• ISSN 0258-2724
  • CN 51-1277/U
  • EI Compendex
  • Scopus
  • Indexed by Core Journals of China, Chinese S&T Journal Citation Reports
  • Chinese S&T Journal Citation Reports
  • Chinese Science Citation Database

Editor-in-Chief: Zhai Wanming

Associate Editor-in-Chief:

Li Hengchao

WANG Kelvin C.P.

Launched: 1954

Sponsored by:Journal of Southwest Jiaotong University

Tel: 028-66367562

Fax: 028-66366552

E-mail: xbz@home.swjtu.edu.cn

Cycle: bi-monthly

Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Display Method:
Vehicle to Grid Optimization Strategy from the Perspective of Supply and Demand Game
DAI Chaohua, YANG Shuai, YE Shengyong, FAN Wenli
 doi: 10.3969/j.issn.0258-2724.20230097
[Abstract](66) [FullText HTML](44) PDF 2170KB(11)
Abstract:

With the explosive development of electric vehicles (EV), the contradiction between the impact of charging load and grid support capacity is highlighted. In response to this problem, an EV charging and discharging (vehicle to grid, V2G) optimization strategy was proposed from the perspective of the game between supply and demand. Firstly, a power price sharing mechanism was constructed to make EV charging and discharging mutually appropriate with base load by combining the characteristics of EV charging and discharging behaviors. Then, for the leader-follower game relationship between the aggregator’s pricing of electricity and the EV users’ charging and discharging behavior selection process, an optimization model was established, whose optimization objectives are maximizing the revenue of the aggregator on the leader level and minimizing the cost of electricity for EV users on the follower level. Finally, the seeker optimization algorithm was used to solve the optimization objectives of both sides separately, and the game cycle was carried out until the equilibrium, so that the optimal electricity pricing strategy and EV charging/discharging strategy were obtained. The simulation results show that the proposed charging and discharging strategy can realize the peak-cutting and valley-filling of the base load curve by the EV charging and discharging load. The variance of the base load curve is reduced by 56.6%, and the difference between peak and valley is decreased by 28.0%. Meanwhile, the charging and discharging cost of EV users is lowered by 40.4%, and the revenue of the aggregator is increased by 40.1%.

Collaborative Computing Method for Highly Available Operation of Digital Twin Manufacturing Equipment
DING Guofu, LIU Mingyuan, XIE Jiaxiang, ZHANG Jian, ZHANG Haizhu, ZHENG Qing
 doi: 10.3969/j.issn.0258-2724.20230074
[Abstract](65) [FullText HTML](55) PDF 2719KB(13)
Abstract:

In digital twin technology, the operation of complex models and production logic consumes a large number of resources. Meanwhile, differences in hardware capabilities and user requirements make it difficult to ensure simulation accuracy and real-time performance, reducing system availability. To address this issue, a real-time synchronous computing framework for digital twin manufacturing equipment that collaboratively processed visualization and logic computation was proposed. Firstly, a digital model of the equipment was constructed based on multidimensional workshop information. According to hardware capabilities and users’ personalized computational needs, a configurable and adaptive system environment mapping method was introduced to adjust simulation fidelity, ensuring the real-time and correct operation of the twin equipment. The process was illustrated by using lighting environment mapping as an example. Secondly, a simulation-based motion logic solving algorithm for a six-degree-of-freedom (6-DOF) manipulator was presented, which used the rendering frame time as the simulation clock advancement step to ensure accurate model motion and synchronization between visualization and computation. The algorithm was generalized for application to other multi-body equipment. Finally, a web-based digital twin workshop modeling and simulation cloud platform was designed and developed. A 6-DOF manipulator and a specific bogie frame processing workshop were used as application cases, and the proposed method was validated. The results show that with the adaptive reduction of mapping fidelity, simulation response speed is increased by 45%, while GPU and CPU resource utilization is effectively reduced. It proves that the method can achieve reasonable resource allocation and efficient system computation while reducing error accumulation, making it a highly available real-time collaborative computing method.

Seismic Testing and Calculation Method of Assembled Bridge Piers with Hybrid Connection of Engineered Cementitious Composites and Assembled Mortise-Tenon Joints
LIN Shangshun, LIN Yongjie, ZHANG Jianshuai, ZHAO Jinbing
 doi: 10.3969/j.issn.0258-2724.20230040
[Abstract](37) [FullText HTML](21) PDF 2935KB(6)
Abstract:

In order to improve the force performance and durability of assembled bridge piers, it was proposed to adopt the assembled bridge piers with hybrid connection of cast-in-place fiber-reinforced engineered cementitious composites (ECC) and assembled mortise and tenon joints and carry out the pseudo-static tests of the bridge piers with different design parameters (depth of the groove and thickness of the cast-in-place ECC layer), so as to establish the experimentally-validated ABAQUS finite-element model. In addition, extended parametric analysis was carried out, and theoretical derivation was conducted on the basis of the finite element parametric analysis. The calculation method of the eigenvalue of the skeleton curve and the restoring force model of the hybrid-connected assembled RC bridge pier were proposed. The results show that the damage mode of the three bridge pier specimens is compression bending damage, and the cast-in-place ECC section of each specimen is not damaged; the changes in the depth of the groove and the height of the cast-in-place ECC section have significant effects on the ductility coefficient and ultimate displacement of the bridge piers. The results of the theoretical analysis coincide with the results of the finite element analysis. The ratio of the calculated values of the formulas to the values of the finite element analysis ranges from 0.85 to 1.14, except for peak displacement, and the results are reliable; the hysteresis curve calculated by the hybrid-connected assembled bridge pier restoring force model matches well with the test curve, which can be used for the elastic-plastic calculation of bridge piers.

Fracture Mechanism of Cologne-Egg Fastener Clips in Rail Corrugation Sections
CUI Xiaolu, PENG Shuangqian, XU Jia, ZHONG Jianke, QI Yayun
 doi: 10.3969/j.issn.0258-2724.20230025
[Abstract](73) [FullText HTML](74) PDF 4197KB(10)
Abstract:

As typical rail damage of the railway, rail corrugation is often accompanied by the fastener clip fracture, which seriously affects the operation safety of the train. Moreover, the small-radius section of the Cologne-egg fastener experiences frequent rail corrugation. To explre the fracture mechanism of Cologne-egg fastener clips, firstly, the finite element model of the wheel set-rail-fastener system, including the complete Cologne-egg fastener model, was established baesd on the field investigation. Then, the resonant response of the Cologne-egg fastener clip was explored, considering the frictional coupling vibration of the wheel-rail system. Finally, the fatigue life of the Cologne-egg fastener clip was compared in the cases of with and without rail corrugation sections, and the fatigue damage of different clips was quantified. The results show that the dominant frequency of the frictional coupling vibration of the wheel-rail system is consistent with the first-mode constraint mode of the Cologne-egg fastener clip in the frequent rail corrugation sections, which indicates that the clip resonance induced by the frictional coupling vibration of the wheel-rail system is the main reason for the Cologne-egg fastener fracture. The frictional coupling vibration of the wheel-rail system is aggravated by the rail corrugation, which makes the clip life of the Cologne-egg fastener in the rail corrugation section decrease by 99.04% compared with that in the absence of rail corrugation section. The clip life is thus only 3.11% of the design clip life. Besides, the Cologne-egg fastener clip on the low gauge side is more prone to fatigue failure in the small-radius curved section, and the failure position is located on the inner side of the rear arch end of the clip.

Site Effects of Linear Method and Modified Horizontal-to-Vertical Spectral Ratio
CHEN XueLiang, CHEN Kelin, LAN Jingyan, LI Xingzhe
 doi: 10.3969/j.issn.0258-2724.20230094
[Abstract](130) [FullText HTML](76) PDF 3851KB(29)
Abstract:

In order to further study the influence of site effects from engineering ground motion, a comparative analysis of site effects from ground motion in the Sichuan strong earthquake area was carried out based on two empirical methods, namely, horizontal-to-vertical spectral ratio (HVSR) and linear inversion. Firstly, 233 sets of strong motion waveforms captured by 17 strong motion stations during the aftershocks of the Wenchuan Earthquake were selected based on the magnitude, station, distance from the epicenter, and other factors. Second, the linear inversion method was used to estimate the quality factor Qs of the S-wave based on the hinged three-stage attenuation model in the Longmenshan area. Meanwhile, two methods, rotational HVSR and multidirectional HVSR, were applied to explain the mechanism of the site effect of azimuthal angle on HVSR in seismic wave propagation. Finally, the possible reasons for the variability of the site effects calculated by the linear inversion and HVSR methods were analyzed, based on which an improved HVSR method was proposed to improve the accuracy of the site effect assessment. The results show that the quality factor of the S-wave in the area is frequency-dependent and approximately equals to 199.2f 0.8 in the range of 0.4–20.0 Hz. The results of HVSR may have a certain dominant direction, and the site effect may increase suddenly at a certain angle with the change of the azimuthal angle, which may be related to the anisotropy of the soil layer at the site. The amplification of vertical ground motion, i.e., the vertical site effect formed by the coupling of soil layer at the site, engineered bedrock, or middle and deep hard rock layers, is the main reason for the difference between HVSR and linear inversion methods.

Adhesion Adaptability of Dual-Source-Powered Electric Multiple Unit on Qinghai−Xizang Line
WANG Bo, LUO Shihui, WANG Chen, QU Tianwei, MA Weihua, LEI Cheng
 doi: 10.3969/j.issn.0258-2724.20220843
[Abstract](129) [FullText HTML](111) PDF 3947KB(30)
Abstract:

In order to analyze the feasibility of a dual-source-powered electric multiple unit (EMU) with enhanced operational efficiency on the Qinghai–Xizang Line (Golmud–Lhasa section), the dynamics model of EMU was established and verified. A dynamic method was adopted to study the relationship among the traction adhesion coefficients, traction force, creepage, and speed for the dual-source-powered EMU and the HXN3 internal combustion locomotive operating on the straight sections, curved sections, and ramps of the Qinghai–Xizang Line. The adhesion characteristics of dual-source-powered EMU under traction conditions were validated by comparing the dynamic responses of the two locomotives. The analysis finds that: 1) The traction adhesion coefficients of the locomotives are proportional to their traction force. Moreover, within the speed range of 40–120 km/h, the adhesion coefficient of the dual-source-powered EMU decreases from 0.19 to 0.09, while the adhesion affluence increases from 59.0% to 85.7%. 2) The adhesion affluence of the dual-source-powered EMU is superior to that of the HXN3 locomotive in both straight sections and ramps, thereby enhancing its ability to cope with low wheel-rail adhesion conditions in harsh external environments and exhibiting better adaptability in plateau environments. 3) In the curved section, by ignoring the structure-induced adhesion reduction difference, the adhesion reduction amplitudes of the dual-source-powered EMU and HXN3 locomotive are 6.3% and 6.8%, respectively, at R300 m curve. At the R800 m curve, the HXN3 locomotive demonstrates an adhesion reduction amplitude of 3.0%, while the adhesion reduction amplitude of the dual-source-powered EMU is below the threshold value, ensuring sufficient adhesion.

Mesoscopic Study on Mechanical and Deformation Behaviors of Reinforced Buried Pipelines Under Vertical Loads
WANG Zhijie, CHENG Biao, YANG Guangqing, GAO Gushun, WANG He
 doi: 10.3969/j.issn.0258-2724.20230046
[Abstract](91) [FullText HTML](55) PDF 3819KB(7)
Abstract:

In order to deeply study the protective effect of geogrid-reinforced buried pipelines under vertical load, indoor model tests were carried out, and a discrete element simulation analysis model was established. The mechanical response and deformation behavior of geogrid-reinforced buried pipelines and surrounding soil systems under vertical load were explored from the mesoscopic level, and the development and evolution laws of the load-settlement curve of loading plate, contact force between particles inside the model, particle displacement, and vertical radial deformation of pipelines were revealed under different buried depths of pipelines and reinforcements. The results show that when the buried depth of the pipeline H is shallow (H = 1.5D, D is the outer diameter of the pipeline model), the ultimate bearing capacity is smaller than that of the pipeline with a large buried depth. Although the settlement of the loading plate is smaller under the same load, the vertical radial deformation of the pipeline is large. After the geogrid above the pipeline is reinforced, the ultimate bearing capacity of the model system is significantly increased, and the vertical radial deformation of the pipeline is reduced. A shallower buried depth of the geogrid indicates a more obvious reinforcement effect. When the buried depth of the geogrid u is reduced from 0.75B to 0.25B, the ultimate bearing capacity is increased by about 57.2%, and the radial deformation of the pipeline is reduced by about 27.9%. In this study, the interaction mechanism among pipelines, soil, and geogrid is revealed from the mesoscopic level, and the mechanical and deformation behavior of geogrid-reinforced protected buried pipelines were visualized.

Refined Traffic Flow Model Based on Cellular Automaton Under Cooperative Vehicle Infrastructure System
LI Xun, CHENG Shuo, WU Dandan, ZHANG Lei, WANG Xiaohua
 doi: 10.3969/j.issn.0258-2724.20220830
[Abstract](58) [FullText HTML](49) PDF 2207KB(11)
Abstract:

The cell size in the classical cellular automaton-based traffic flow model makes it difficult to express the position relationship of vehicles accurately. Therefore, a scheme to improve the symmetric two-lane cellular automaton (STCA) model by refining the cell size was presented. Firstly, the position, speed, acceleration, and interaction of vehicles in the urban road two-lane environment were analyzed, and the numerical model of these characteristics was built based on the cellular automaton. Especially, the road size and the cellular representation form in the model were improved to solve the problem that the existing traffic flow model based on cellular automaton does not conform to the vehicle driving phenomenon on the actual road. Secondly, according to the real vehicle infrastructure environment, road congestion, lane changing, and other behaviors in the STCA model were redefined, and the lane rules were combined with the refined lane model. A new traffic flow model, namely STCA-CH, was established. Finally, the model was compared with STCA, STCA-I, STCA-S, and STCA-M models, and the validity of the STCA-CH model was verified by analyzing the average speed, average flow, lane changing frequency, and space-time diagram under different vehicle densities. The results show that the lane changing frequency of the STCA-CH model is about 21.14% higher than that of the STCA-M model, and the maximum average flow is about 25.76%, 11.30%, and 3.75% higher than that of the STCA-I, STCA-S, and STCA-M models respectively.

Fixed Point Evolution Algorithm
SU Qinghua, HONG Nan, HU Zhongbo
 doi: 10.3969/j.issn.0258-2724.20220079
[Abstract](78) [FullText HTML](40) PDF 3044KB(15)
Abstract:

In order to design an efficient and robust evolution algorithm, the fixed point iteration idea in solving equations was first introduced into the optimization field. The optimization process of an evolution algorithm was regarded as the gradual display process of the fixed point of an equation in an iterative framework. On this basis, a novel evolution algorithm based on a mathematical model was developed, named fixed point evolution algorithm (FPEA). The reproduction operator of FPEA is a quadratic polynomial which is derived from a fixed point iteration model with the Aitken method. The overall framework of FPEA inherits the population-based iterative model of traditional evolution algorithms such as differential evolution algorithm. The experimental results show that the average ranking of the optimal value of FPEA ranks first among all the compared algorithms on benchmark functions CEC2014 and CEC2019. The proposed algorithm can achieve the highest solution accuracy with a low computational overhead on four engineering constraint design problems among the compared algorithms including CSA and GPE.

Short-Circuit Characteristics Analysis of New Continuous Cable Traction Power Supply System
ZHANG Liyan, LUO Bo, ZHENG Xing
 doi: 10.3969/j.issn.0258-2724.20220290
[Abstract](43) [FullText HTML](30) PDF 2245KB(3)
Abstract:

New continuous cable traction power supply system (CCTPSS) can achieve long-distance transmission and reduce the number of electric phases. However, the two-stage power supply mode leads to the complex structure of the system. In order to reveal the short-circuit characteristics of CCTPSS, the two-port network parameters of traction cable and catenary-rail of unit length were established. Each sub-network was cascaded and equated with a two-port network, which was then transformed into a Ⅱ-type circuit for modeling the distribution parameters of the traction cable and catenary-rail of any length. The locomotive voltage drops after short circuit of catenary. Therefore, considering the coupling relationship between the train and the network, the short-circuit current and voltage were solved by iterative calculation. The accuracy of the calculation method was validated by simulation. Finally, the electrical characteristics of different short-circuit types were analyzed, with emphasis placed on the influence of distributed capacitance on short-circuit current and voltage. The results show that the distributed capacitance can increase the short-circuit current and, under different short-circuit conditions, the output voltage of traction transformer. The short-circuit current of catenary is jointly provided by traction transformers on both sides, and the farther away from the short-circuit point is, the less current is provided. The cable phase-to-phase short circuit has the greatest impact on the operation of the non-fault-circuit locomotive.

Comprehensive Comparison of Inversion Performance of Urban Traffic Congestion Source Parameters
ZHAO Xueting, HU Liwei
 doi: 10.3969/j.issn.0258-2724.20230008
[Abstract](57) [FullText HTML](40) PDF 2228KB(5)
Abstract:

In order to accurately grasp the main parameters and diffusion and propagation laws inherent in urban traffic congestion sources and realize scientific control of traffic congestion sources, the Gaussian plume model for air pollutant dispersion was introduced and improved. The urban traffic congestion sources were divided into continuous traffic flow and a series of intermittent traffic flow, so as to realize the structural analysis of the Gaussian plume model. Then, three test functions, namely Griewank, Schaffer, and Rastrigin were used to test the “single point source” parameter inversion algorithm, and the seeker optimization algorithm was selected. Finally, the performance of the five typical objective functions with different numbers of parameters (one, two, and three) was evaluated in three dimensions based on the observed traffic congestion source data. The results show that in the one-parameter case, the stability of the objective function based on the sum of squared deviations of traffic density per unit area is better, and the confidence interval of the absolute value of the relative deviation of the inverse source strength is 38.38% ± 9.94%; the number of experiments less than 50.00% accounts for 84.52% of all experiments, and the stability of each objective function is better. In the two-parameter case of source strength inversion, the accuracy of the objective function based on the root-mean-square error of traffic density per unit area in the form of logarithmic transformation is the highest, and the confidence interval of the absolute value of the relative deviation of source strength inversion is 51.42% ± 9.84%; the number of experiments less than 50.00% accounts for 92.16% of all experiments. In terms of inversion location, the accuracy of the objective function based on the sum of squared deviations of traffic density per unit area is the best (absolute value of position deviation inversion is 37.22 m ± 10.64 m), and the stability of the objective function based on correlation coefficient is the strongest (coefficient of variation is 0.022). In the three-parameter case, the accuracy inversion results are more consistent with those in the two-parameter case, and the source strength stability of each objective function is poor except for the objective function in the form of logarithmic transformation, but the position stability is better.

First-Order Logic Clause Selection Method Based on Multi-criteria Decision Making
ZENG Guoyan, XU Yang, CHEN Shuwei, JIANG Shipan
 doi: 10.3969/j.issn.0258-2724.20230023
[Abstract](76) [FullText HTML](45) PDF 1744KB(8)
Abstract:

First-order logic-based automatic theorem provers (ATPs) are important for the research on knowledge representation and automatic reasoning, and heuristic strategies are a critical research topic to enhance the performance of ATPs. Mainstream heuristic strategies select clauses by describing clause properties and then determining the priority of the properties. However, the priority of properties is subject to human factors, and it takes a long time to evaluate clauses. A new multi-criteria decision making (MCDM) clause evaluation method was proposed based on the standard contradiction separation (S-CS) rule. Firstly, the entropy weight method was used to objectively assign weights to clause properties. Secondly, preference ranking organization method for enrichment evaluations (PROMETHEE Ⅱ) was combined to evaluate the clauses and obtain the complete order of the clauses. Finally, the proposed MCDM method was applied to ATPs CSE 1.5 (contradiction separation extension 1.5), Vampire 4.7, and Eprover (E 2.6) to form new ATPs MCDM_CSE, MCDM_V, and MCDM_E. The theorems in first-order form (FOF) from the international theorem provers problem library Thousands of Problems for Theorem Provers (TPTP) were tested on MCDM_CSE, and the Conference on Automated Deduction (CADE) 2022 competition (FOF division) was tested on MCDM_V and MCDM_E. The experiments show that MCDM_CSE proves 151 more theorems (from TPTP) than CSE 1.5 and proves 5 theorems unproved by Vampire 4.7, 41 theorems unproved by E 2.6, and 293 theorems unproved by Prover9. In a shorter average time, MCDM_V proves 6 more theorems (from CADE 2022) than Vampire 4.7, and MCDM_E proves 8 more theorems than E 2.6.

Simulation of Dynamic Coupling of Metro-Earth-Grid for DC Interference in Rail Transit
LIU Wei, LI Songyuan, TANG Yuning
 doi: 10.3969/j.issn.0258-2724.20230052
[Abstract](54) [FullText HTML](24) PDF 2077KB(5)
Abstract:

In response to the problem that direct current (DC) bias current of neutral grounded transformer is affected by dynamic stray current leakage and depot grounding of rail transit, a metro-earth-grid coupling model of stray current distribution and diffusion under multi-train operation was proposed, and the complex image method was used to calculate the earth potential. The self and mutual resistance coefficients of grounding grids were defined, and the coupling relationship between DC bias current and earth potential was proposed. The field-circuit coupling model of earth potential and DC bias current was built according to the topology of stray current intrusion path. A scaled-down simulation test of stray current intrusion into the grid for rail transit was designed, and tests and model calculation were conducted for verification. The results show that the maximum error between the experimental data and the model calculation data is 8.41%. The rail-to-earth transition resistance increases from 3.00 Ω·km to 15.00 Ω·km, and the absolute average of DC bias current decreases by 82.4%. Using a blocking connection device between the car depot and the main line can reduce DC bias current by 23.45% compared with using a unidirectional conduction device.

Identification Method for Key Nodes in En-Route Network
TIAN Wen, FANG Qin, ZHOU Xuefang, SONG Jinjin
 doi: 10.3969/j.issn.0258-2724.20220532
[Abstract](119) [FullText HTML](26) PDF 2045KB(13)
Abstract:

Accurate identification of key nodes is of great significance for enhancing network resilience and improving operational capabilities. In order to improve the identification accuracy of key nodes in the en-route network, a comprehensive evaluation method based on the technique for order preference by similarity to an ideal solution (TOPSIS)-grey correlation analysis method and a node classification method for the en-route network were proposed. Firstly, an evaluation index system of key nodes in the en-route network was constructed from three perspectives: complex network characteristics, traffic volume, and vulnerability. Then, the relative entropy was introduced to improve the TOPSIS method, and the importance of en-route waypoints was comprehensively evaluated by combining this method with the grey correlation analysis method. The K-means clustering method was used to effectively divide the levels of en-route waypoints. Finally, key node identification was carried out based on the actual operation data of civil air traffic management. It finds that the results obtained by the constructed evaluation index system of key nodes in the en-route network are more comprehensive than the evaluation results of a single index. The improved TOPSIS-grey correlation analysis is more accurate than the traditional TOPSIS method. The proposed identification method finds that there are 29 key nodes in the typical busy en-route network in Eastern China, which play a key role in the network structure and traffic volume.

Extremum Conditions of Response of Maglev Guideway Under Train Loads
XIANG Huoyue, LIU Kehong, LI Yongle
 doi: 10.3969/j.issn.0258-2724.20220835
[Abstract](57) [FullText HTML](23) PDF 2268KB(12)
Abstract:

To reveal the variation law of dynamic response of maglev guideways, maglev trains were simplified as moving uniform loads, and analytical methods were employed to obtain the analytical solutions for dynamic response of simply supported guideways. The variation laws of the maximum response of guideways with train speed and guideway span were discussed, and the extremum conditions of response of maglev guideways were derived, which were verified by finite element and train-bridge coupling vibration methods. The results show that under the condition of a large train-guideway span ratio, the maximum response of midspan increases with fluctuations as the train speed increases and has extremums. Guideway response also has similar change laws with the variations of guideway span, mass, and other parameters. When the product of span and speed is a specific constant, or the product of the first-order vertical frequency and span of guideway is a specific time the train speed, the guideway produces vibration isolation.

Maximum Temperature in Bifurcated Tunnel Based on Synergistic Effect of Longitudinal Ventilation and Air Curtain
LI Tao, YANG Yunping, MI Chun, CHEN Zhengquan, WANG Chunxiang, CHEN Longfei, ZHANG Yuchun
 doi: 10.3969/j.issn.0258-2724.20230157
[Abstract](97) [FullText HTML](32) PDF 2379KB(10)
Abstract:

To investigate the effect of synergistic longitudinal ventilation and air curtain on the control of tunnel fire smoke in urban bifurcated tunnels, the 1∶10 small-sized bifurcated tunnel fire experiments were conducted, and the along-travel and maximum temperatures of bifurcated tunnels under the synergistic effect of longitudinal ventilation and air curtains were analyzed by taking into account the variables of longitudinal ventilation, jet velocity, angle, and thickness of air curtain. Firstly, the smoke and heat insulation effect of the air curtain was analyzed through 57 sets of small-sized tunnel fire experiments. Then, based on the dimensionless empirical correlation formula for the maximum temperature rise of the ceiling in a tunnel fire, a model of the maximum temperature rise under the synergistic effect of air curtain and longitudinal ventilation was constructed at a fixed heat release rate of 47.9 kW. Finally, the experimental values of the maximum temperature rise under different working conditions were compared with the predicted values of the theoretical models of the maximum temperature rise. The results show that an air curtain can effectively help longitudinal ventilation reduce the temperature in the main tunnel by up to 420 ℃ while effectively preventing smoke from entering the bifurcated tunnels. When the jet velocity of the air curtain is small, the increase in longitudinal wind speed can effectively prevent the accumulation of smoke in the bifurcation and improve the insulation efficiency of the air curtain on the smoke. In addition, the temperature of the smoke at the tunnel bifurcation point can be reduced by up to 170 ℃. The constructed theoretical model of the maximum temperature rise is compared with the experimental results, and the error between them is less than 10%.

Acoustic Emission Characteristics of Loose Particles in Direct Shear Test at Different Rates
WU Xin, LUO Xiaoyu, LI Longcan, LIU Yonghong, ZHU Xu, LIN Huali
 doi: 10.3969/j.issn.0258-2724.20230179
[Abstract](66) [FullText HTML](27) PDF 2844KB(12)
Abstract:

Loose particle accumulations are widely present in nature and industrial production activities. In order to study their mechanical properties and instability processes, acoustic emission (AE) technology was used to explore the evolution law of acoustic characteristics of loose particles in a shear process. Firstly, the AE characteristic parameters of loose particles at different shear rates were analyzed. Then, the AE evolution stages were divided based on the mechanical characteristics of the loading process. Finally, the AE evolution law of loose particles under shear failure was further verified with spectral changes and the proportion of wavelet packet energy. The results show that the energy and ringing count increase gradually with the shear process. The faster the shear rate, the larger the increases of energy and ringing count. The number ratio of small events to large events (b value) decreases gradually during the shear process, and the larger the shear rate, the smaller the b value. The shear strength of particles at different rates is about 140 kPa, and the peak shear force is about 400 N. The changes of ringing count, AE energy, and b value during shear motion are closely related to shear failure stage. The spectral barycenter gradually decreases in the shear process from about 350 kHz to 250 kHz. Meanwhile, the energy proportion of the low frequency band increases, and the energy proportion of the high frequency band decreases accordingly, which results in a spectral barycenter constantly moving down.

Influence of Temperature-Varying Characteristics on Operating Performance of Alpine Electric Multiple Units
QI Yayun, LI Long, SHI Huailong, SONG Ye, DAI Huanyun
 doi: 10.3969/j.issn.0258-2724.20220876
[Abstract](136) [FullText HTML](79) PDF 3718KB(29)
Abstract:

The service environment of alpine electric multiple units (EMUs) is affected by temperature for a long time, and the vehicle suspension element parameters and under-rail parameters have strong seasonal variation characteristics. To investigate the influence of temperature-varying characteristics of rubber elements on the operating performance of alpine EMUs, a multi-body dynamics model of alpine EMUs was established to analyze the vehicle dynamics characteristics under different temperatures. Then, the wheel wear characteristics at different temperatures were analyzed by the Jendel wear model. Finally, the wheel surface fatigue index was proposed based on the fatigue prediction model. The results show that the temperature variation will change the stiffness and damping value of suspension parameters, and the stiffness of suspension parameters increases as the temperature decreases. The dynamic performance of the EMUs decreases at low temperatures. The wear of the vehicle increases as the temperature decreases. After 200 000 miles of operation, the largest depth of wheel wear is found at a temperature of −40 ℃, which is 6.2% greater than the depth of wheel wear at a temperature of 20 ℃. The surface contact fatigue index gradually increases as the temperature decreases, with wheel surface fatigue indexes being 6.4648×10−4, 6.6150×10−4, and 6.7885×10−4 at temperatures of 20 ℃, −20 ℃, and −40 ℃, respectively. Temperature-varying characteristics have a large effect on the suspension parameters of alpine EMUs, with dynamic performance deteriorating at low temperatures, wear intensifying, and wheel surface fatigue increasing.

Centrifuge Test on Bearing Capacity of Energy Piles in Sand Affected by Thermal-Cool Cycles
CHEN Long, HU Yifan, CHEN Yonghui, ZHU Lei, ZHANG Tilang
 doi: 10.3969/j.issn.0258-2724.20220740
[Abstract](114) [FullText HTML](60) PDF 2453KB(8)
Abstract:

To study the bearing capacity of energy piles in sand affected by thermal-cool cycles, a centrifuge model test on slender energy piles buried in Fengpu sand with different compactions was carried out. The change rules of the axial force, side friction, and individual bearing capacity of energy piles were obtained and compared under 20 thermal-cool cycles in the test. The test results show that the axial force of the energy pile decays gradually and tends to be stable with increasing thermal-cool cycles. The maximum axial force attenuation value of the energy pile buried in the sand with medium compaction is much larger than that buried in the dense sand. During thermal-cool cycles, for energy piles buried in the sand with medium compaction, a neutral point is located at the bottom half of the pile. Positive additional side friction is generated above the neutral point during cool cycles, and negative additional side friction is generated underneath the neutral point. Oppositely, during thermal cycles, negative additional side friction appears above the neutral point, and positive additional side friction is underneath the neutral point. The dense sand has an obvious constraint effect on the lower part of energy piles. Positive additional side friction is distributed along the pile during cool cycles because the pile moves downward relative to the surrounding soil. During thermal cycles, the additional side friction is negative. The bearing capacity of the energy piles will be reduced because of the long-term temperature cycles. The bearing capacity of the energy piles buried in the dense sand and sand with medium compaction is reduced by 7.3% and 15.6%, compared with the prototype pile. The bearing capacity of the prototype pile and energy piles buried in the dense sand is 11% larger than that of the prototype pile buried in the sand with medium compaction. Therefore, reasonable measures should be taken to meet the bearing requirements of energy piles when buried in sandy layers with different compactions in actual engineering.

Ride Comfort Analysis of Suspension System of Mining Dump Truck Based on AMESim
LIU Qihang, FENG Handui, LIU Shen, LI Beibei, LIU Xiumei
 doi: 10.3969/j.issn.0258-2724.20230135
[Abstract](143) [FullText HTML](106) PDF 3597KB(32)
Abstract:

Mining dump trucks are mainly used for small-scale mine transportation, often run on poor roads or with serious overloading and other conditions. Hydro-pneumatic suspension is widely used in large construction vehicles due to its nonlinear characteristics of stiffness and damping, which can better adapt to external load excitation changes. For the XDR80t mining dump truck produced by XCMG, the acceleration data of the tire center of mass and body were collected, and a method based on frequency domain integral was proposed to obtain the relative displacement data of the piston rod. AMESim simulation platform was used to establish a mechanical and hydraulic co-simulation model, and the variation trend of body vibration characteristics under different structural parameters of suspension was investigated. The results show that the damping hole diameter has a more obvious influence on the vibration state of the body. When the damping hole diameter is changed from 8 mm to 14 mm, the peak value of acceleration is reduced by about 49.27%, and the root mean square (RMS) value is reduced by about 49.42%. However, the pitch angle shows an increasing trend. With the increase in cylinder/rod diameter from 180/150 mm to 200/170 mm, the peak value of acceleration and RMS value decrease by 16.84% and 18.62%. When the pre-charge pressure is increased from 1.5 MPa to 2.25 MPa, the peak value of acceleration and RMS value decrease by 27.67% and 27.49%, and the pitch angle declines.

Influence Mechanism of Long-Span Arch Bridge Deformation on Running Stability of High-Speed Trains Under Crosswind
LI Xiaozhen, ZHOU Yanxi, WANG Ming
 doi: 10.3969/j.issn.0258-2724.20220598
[Abstract](206) [FullText HTML](141) PDF 3947KB(52)
Abstract:

In order to explore the influence mechanism of arch bridge deformation on the running stability of the train under crosswind, the horizontal and vertical displacement of the mid-span was obtained through the wind, vehicle, and bridge coupling system, and the running stability of the train under different wind speeds and train speeds was analyzed. The contribution of bridge deformation to horizontal and vertical acceleration of the train in the wind, vehicle, and bridge system was quantified. Combined with the sensitive wavelength of the acceleration response of the train and the time-frequency characteristic of bridge deformation, the influence mechanism of bridge deformation on running stability was analyzed. The results show that the vertical displacement difference of the bridge is smaller than the horizontal displacement difference, and the main displacement is caused by the vehicle-induced bridge deformation. The maximum value reaches −9.2 mm. Under the action of train and wind load, the horizontal and vertical displacement of the bridge is more significant, but its influence on the stability of the train is mainly reflected in the position of the junction pier, which is about four times the response of other positions. Except for the junction pier area, the running stability of the train on the bridge is mainly determined by the wind-induced train vibration and track irregularity. The spectral density distribution of horizontal and vertical acceleration power of the train is closely related to the wavelength of track irregularity, and the corresponding sensitive wavelength range is less than 120 m. The horizontal and vertical acceleration of the train is mainly affected by the bridge deformation caused by the vehicle load, while the bridge deformation caused by wind load is mainly distributed in the main span, and the wavelength is larger than 120 m. Therefore, it does not exert a significant impact on the acceleration of the train.

Review on Intelligent Image Recognition of Apparent Diseases of Stay Cable
ZHANG Hong, JIANG Xiaogang, ZHU Zhiwei, XIA Runchuan, ZHOU Jianting
 doi: 10.3969/j.issn.0258-2724.20220647
[Abstract](199) [FullText HTML](79) PDF 2161KB(36)
Abstract:

The stay cable is one of the main load-bearing elements of cable-stayed bridges, and the disease of its outer sheath is easy to penetrate inside the cable and affect the health of the steel wire. Therefore, it is significant to use the video image method to intelligently identify the apparent disease of the cable. Based on image recognition, the methods of apparent disease recognition for stay cable were systematically reviewed from two aspects: traditional image detection and deep learning. The basic principles and application effects of each method were introduced, and the current detection examples were analyzed. Some cutting-edge deep learning methods were introduced to provide a reference for the apparent detection of cables. The main features of various methods were summarized, and the problems existing in the current detection were discussed and prospected. The deep learning model-based image recognition method had better recognition accuracy and algorithm robustness, stronger learning ability and adaptability, and optimal comprehensive image defect recognition effect, but there were still difficulties such as the difficult balance between detection accuracy and speed, large image data demand, and high labeling cost. To this end, detection methods could be improved by improving image quality, constructing more semi-supervised and unsupervised deep learning models, and enhancing the learning ability of detection models.

Axial Compression Performance of Concrete Columns Confined by Ultra-High Performance Concrete Reinforced with High-Strength Steel Wire Cloth
DENG Zongcai, WANG Tianyu
 doi: 10.3969/j.issn.0258-2724.20230096
[Abstract](58) [FullText HTML](34) PDF 2963KB(8)
Abstract:

In order to master the constraint effect of new high-strength steel wire cloth reinforced ultra-high performance concrete (UHPC), a study was conducted on the influence of the surface density and number of layers of high-strength steel wire cloth on the axial compression performance of confined concrete columns. Firstly, the constraint effect of high-strength steel wire cloth reinforced UHPC was evaluated using Poisson’s ratio, ductility index, and toughness index. Secondly, a lateral constraining force model of the composite constraining layer was established considering the constraining force provided by high-strength steel wire cloth and UHPC. Finally, a constitutive model of axial compression of confined concrete was established based on the Ottosen failure criterion and an effective constraint index. The results show that the confined column exhibits obvious ductile failure under compression, and the high-strength steel wire cloth reinforced UHPC confinement system can effectively suppress crack development and slow down the stiffness degradation of the specimen in the later stage of loading. Compared with the unconfined column, confined columns have maximum increases of 147.0%, 104.0%, and 58.0% in ultimate bearing capacity, peak compressive strain, and peak stress, respectively. When the number of layers of high-strength steel wire cloth increases from 1 to 2, and the surface density increases to 3.3 times, the ultimate bearing capacity, peak compressive strain, and peak stress of the confined column increase by 8.4%, 29.3%, and 15.8%, respectively, while the ductility index and toughness index increase by 50.3% and 44.2%, respectively. The model established in this paper highly agrees with the experimental results compared with the classical constitutive model of axial compression of confined concrete.

Experimental Study and Numerical Analysis of Shear Behavior of Studs Embedded in Engineered Cementitious Composite Bridge Decks
LIU Yiming, ZHANG Qinghua, BU Yizhi
 doi: 10.3969/j.issn.0258-2724.20220824
[Abstract](143) [FullText HTML](73) PDF 6132KB(17)
Abstract:

In order to study the shear behavior of studs embedded in engineered cementitious composites (ECC), model tests and the numerical analysis of finite elements were carried out. The failure mode of studs embedded in ECC was determined based on push-out model tests. Then, parametric numerical analysis of finite element was performed to elucidate the effects of stud diameter, height/diameter ratio of stud, tensile strength of stud, and compressive strength of ECC on the shear behavior and failure mode of connectors. Finally, a method for calculating the shear capacity of studs embedded in ECC was established according to the above research. The results show that the shear strength of studs embedded in ECC is closely related to the failure mode of the push-out model. When the push-out model fails due to ECC crushing, the shear strength of the connector depends on the compressive properties of ECC. When the push-out model fails due to stud fracture, the shear strength of the connector depends on the tensile strength of the stud and compressive properties of ECC; increasing the compressive strength of ECC and reducing the height/diameter ratio of the stud both can improve the shear stiffness of the connector, but the tensile strength of the stud has a slight effect on the shear stiffness of the connector. When the height/diameter ratio of the stud is lower than 4.60, the shear strength of the stud reduces with the decreasing height/diameter ratio of the stud. Studs with a height/diameter ratio of greater than 4.60 are recommended to serve as a shear connector applied in steel-ECC bridge decks.

Vortex-Induced Vibration Response of Bridges Considering Both Spanwise Variation of Vibration Amplitude and Correlation of Aerodynamic Forces
YANG Meng, WANG Yunfei, ZHAO Jiabin, ZHOU Jing, WANG Yongjing, LI Yongle
 doi: 10.3969/j.issn.0258-2724.20220714
[Abstract](185) [FullText HTML](71) PDF 1996KB(28)
Abstract:

This paper aims to study the effect of spanwise variation of vibration amplitude and spanwise correlation of the nonlinear aerodynamic forces on the vortex-induced vibration (VIV) response of bridges. Firstly, a nonlinear aerodynamic force model of the bridge represented by polynomial functions of vibration amplitude was introduced. Secondly, on the basis of the two-dimensional VIV (2D VIV) analysis method, an approach for predicting the three-dimensional VIV (3D VIV) amplitude response with consideration of both spanwise variation of vibration amplitude and spanwise correlation of aerodynamic forces was proposed through theoretical analysis. Finally, by taking a 1 700 m long-span suspension bridge as an example, the nonlinear aerodynamic force parameters of vertical VIV of the bridge girder at different angles of wind attack were extracted through a wind tunnel test. Then, the VIV amplitude response of the suspension bridge under a first-order positive symmetrical vertical mode at different angles of wind attack was analyzed. The results prove that when the aerodynamic forces are assumed to be fully correlated along the span, the 3D analysis under different wind speeds leads to a significantly higher VIV amplitude response (about 19%) as compared with the 2D analysis method due to the effect of spanwise variation of vibration amplitude of the aerodynamic forces. However, when the aerodynamic forces are assumed to be partially correlated along the span, the VIV amplitude response by 3D analysis is reduced significantly, and the reduction range is about 16%–30% under most wind speeds and about 70% under certain wind speeds. It is proved that it is important to accurately predict the VIV amplitude response of long-span bridges by considering the spanwise variation of vibration amplitude and spanwise partial correlation of aerodynamic forces. The approach proposed in this paper is also applicable to the analysis of torsional VIV or VIV at higher-order modes.

Display Method:
Crossing Power Governance Approach of Continuous Power Supply System in Electrified Railway
LI Qunzhan, PENG You, HUANG Xiaohong, WANG Hanlin, REN Tao
2024, 59(6): 1245-1255.   doi: 10.3969/j.issn.0258-2724.20220887
[Abstract](176) [FullText HTML](59) PDF 2232KB(36)
Abstract:

A novel crossing power governance approach was proposed to mitigate the effects of crossing power in the traction power supply system while taking regenerative braking energy utilization into account. First, the power flow under different operating conditions was derived based on the structure of the continuous power supply system, and the method for detecting crossing power was analyzed. Second, a power transfer and energy storage unit was set using the single-phase combined co-phase traction substation, and the working mechanism of the improved system was analyzed. Then, a cooperative control strategy of crossing power governance was proposed by combining the upper control strategy of power distribution and negative sequence satisfactory compensation with the lower control strategy of converter control. Finally, the amount of crossing power was calculated using the experimental data of a railway line, and the cost-effectiveness of the governance measure was evaluated. In addition, the accuracy and efficacy of the proposed scheme were verified by simulation. The research results show that the proposed system and its control strategy can effectively mitigate the crossing power and regenerative braking energy, with the utilization rate of the crossing power of the power transfer and energy storage unit exceeding 70% in the case of traction substation and traction network loss. The system is highly economical and feasible.

Modeling and Simulation of Inductive Coupling Interference from Suburban Railways to Buried Pipelines
XIE Shaofeng, LI Weilan, HUANG Darui, ZHONG Fan
2024, 59(6): 1256-1265, 1304.   doi: 10.3969/j.issn.0258-2724.20220652
[Abstract](72) [FullText HTML](35) PDF 3287KB(33)
Abstract:

With the rapid development of suburban railways and oil and gas pipelines, parallel laying or cross-laying is inevitable for suburban railways and buried pipelines. In order to assess the impact of the traction power supply system of suburban railways on the safe operation of oil and gas pipelines, firstly, the mathematical model of the alternating current (AC) traction power supply system of the suburban railways and the adjacent buried pipelines was established, and the simulation based on CDEGS software was conducted. Next, the two cases of the oblique approach and parallel approach were unified by the equivalent distance method. The influence mechanism of the traction power supply system of the suburban railways on the adjacent buried pipeline was investigated, and the influence of factors including soil resistivity, distance between the conductor and the buried pipeline, locomotive load current, parallel length of railway and buried pipeline, pipeline coating resistivity, and number of current harmonics of electric multiple units on the inductive coupling voltage distribution along the pipeline was investigated. Finally, combined with the setting of a through ground line, four schemes to suppress the inductive coupling voltage were put forward for comparative analysis. The results show that the error of the equivalent distance method is within 5% when the ratio of the maximum distance to the minimum distance between the traction power supply system of the suburban railway and the buried pipeline is less than 4.5. The maximum value of the inductive coupling voltage of the pipeline increases with increasing soil resistivity. The decrease in the inductive coupling voltage is 50.6% when the distance between the suburban railway and the buried pipeline varies from 50 m to 250 m. The increase in the inductive coupling voltage rises significantly when the locomotive load current varies from 200 A to 1 000 A. The inductive coupling voltage increases from 22.6 V to 170.7 V when the parallel length varies from 2 km to 10 km. The harmonic content and the number of harmonics have a significant influence on the inductive coupling voltage. The best inductive coupling voltage suppression effect is achieved by adding a return line on the basis of the through ground line.

Improved and Fast Global Maximum Power Point Tracking Algorithm of Photovoltaic Power Generation System
ZHOU Guohua, XUE Ning, BI Qiang
2024, 59(6): 1266-1274.   doi: 10.3969/j.issn.0258-2724.20220863
[Abstract](83) [FullText HTML](28) PDF 2823KB(27)
Abstract:

In order to improve the energy utilization of photovoltaic (PV) power generation under partial shading conditions (PSCs), an improved and fast global maximum power point tracking (GMPPT) algorithm was proposed. Firstly, the output characteristics of PV array under PSCs were researched, and the output curve of PV array was divided into constant current region (CCR) and constant voltage region (CVR) according to the relationship between knee point and open circuit voltage. Then, the operation principles of the traditional maximum power trapezium (MPT) algorithm and the improved and fast GMPPT algorithm were analyzed. The improved and fast GMPPT algorithm is based on the MPT algorithm, where the search interval is limited by dynamic upper and lower limits of voltage, and CCR with a long adjustment time was skipped to further improve the tracking speed. Finally, the effectiveness of the proposed algorithm was verified by simulation and experiment. The experimental results reveal that the minimum tracking time of the improved and fast GMPPT algorithm is 4.0 s, and the scanning voltage and the energy loss of the proposed algorithm are 17.34 V and 98.19 J, respectively. Compared with the traditional global scanning algorithm and the MPT algorithm, the proposed algorithm decreases tracking time by 68.25% and 68.00%, lowers scanning voltage by 74.86% and 75.63%, and reduces energy loss by 58.19% and 62.31%, respectively.

Thermal Aging Characteristics of Vehicle-Mounted Cable Terminal Stress Control Tube and Its Influence on Insulation Performance
SUN Chuanming, LIU Kai, ZHANG Pengpeng, XIN Dongli, GAO Bo, LI Guangjian, WU Guangning
2024, 59(6): 1275-1284.   doi: 10.3969/j.issn.0258-2724.20220164
[Abstract](116) [FullText HTML](59) PDF 3008KB(55)
Abstract:

In order to determine the thermal aging characteristics of the vehicle-mounted cable terminal stress control tube and its influence on the insulation performance of cable terminal under thermal aging conditions, firstly, the macro-dielectric characteristics and micro-aging law of vehicle-mounted cable terminal stress control tube were determined through experimental research. Secondly, based on the analysis of the electrical conductivity, polarization, and loss characteristics of the stress tube material under thermal aging, the dielectric characteristic curves under different aging periods were obtained. Finally, a finite element model of the electric field of the vehicle-mounted cable terminal was established by considering the aging characteristics of the stress control tube, and the electric field distribution of the cable terminal of the stress control tube was calculated based on the dielectric parameters under thermal aging. The results show that the electrical conductivity increases most significantly at 140 ℃ and reaches the maximum value of 1.1 × 10−10 S/m at a field intensity of 50 kV/m. The relative dielectric constant reaches the minimum value of 14.00 at high temperature (140 ℃) for 20 days. In addition, trap hindrances such as folding and breaking of polymer long chain are enhanced during pyrolysis reaction, and the dielectric loss increases. In terms of functional group characteristics and microstructure of the stress control tube, thermal aging results in pyrolytic polymerization of olefin polymers in stress control tube materials, forming chemical stereoscopic defects. In addition, the cracking of polymer spherulites and the formation of inorganic oxidation products on the surface of the stress control tube sample are intensified, and the physical and chemical properties of the sample surface are changed. Simulation results show that under thermal aging conditions, the electric field distortion area inside the cable terminal presents a trend of expanding, creeps along the stress control tube towards the terminal high voltage, and finally stabilizes at the junction of the main insulation layer of ethylene propylene rubber (EPR) and stress control tube.

Direct Current Ampacity of 35 kV Alternating Current Cross-Linked Polyethylene Cables Under Various Direct Current Topologies and Laying Environments
ZHANG Tianyin, WANG Qilong, WANG Xin, JIN Yang, YANG Min, CHEN Xiangrong
2024, 59(6): 1285-1293, 1304.   doi: 10.3969/j.issn.0258-2724.20220704
[Abstract](99) [FullText HTML](37) PDF 3295KB(30)
Abstract:

Converting alternating current (AC) cables into direct current (DC) operation is of great significance to achieve new energy generation connected to the grid and increase power supply capacity. A 35 kV AC cross-linked polyethylene (XLPE) cable was taken as the research object, and temperature field simulation of the three-core AC cable was carried out through the finite element method under three kinds of DC topologies: three-wire bipole, monopole, and bipole. At the same time, common influencing factors in the distribution network were considered, such as distance from hot water pipes, cable cluster laying, and current imbalance, so as to explore the influence of these factors on the ampacity of the cable when the AC cable was changed to the DC operation. The results show that under the same operating temperature, the 35 kV AC XLPE cable has the smallest ampacity when operating under the monopolar DC topology and the largest ampacity under the three-wire bipolar DC topology. When the horizontal distance between AC cable and urban water supply pipes is 2.0 m, and the vertical distance is 0.5 m, the ampacity of cables operating under the above kinds of DC topologies is reduced by about 3.0%. The maximum ampacity can be increased by 90 A as the asynchronous peak value is loaded when the cable cluster is laid. The cable ampacity increases first and then decreases with increasing current imbalance, and it reaches the maximum value when the current imbalance is 0. The research results can provide some reference for converting 35 kV AC XLPE cables into DC operation.

Lightweight Detection of Railway Object Intrusion Based on Spectral Pooling and Shuffled-Convolutional Block Attention Module Enhancement
CHEN Yong, WANG Zhen, ZHANG Jiaojiao
2024, 59(6): 1294-1304.   doi: 10.3969/j.issn.0258-2724.20220074
[Abstract](91) [FullText HTML](37) PDF 3198KB(23)
Abstract:

In infrared low-light scenes, railway object intrusion detection faces low detection accuracy, and it is difficult to achieve lightweight real-time detection. Therefore, a lightweight detection method of railway object intrusion based on convolutional block attention module (CBAM) enhancement was proposed. Firstly, the Darknet53 feature extraction network was improved by deep separable convolution to achieve lightweight extraction of railway object intrusion characteristics in infrared low-light scenes. Secondly, semantic-guided infrared spectral pooling was used for feature enhancement to improve the feature quality of infrared image downsampling. Then, a shuffled-CBAM was proposed to achieve feature extraction and fusion of key infrared targets and improve the accuracy of infrared target detection. Finally, the lightweight anchor-free network was used to predict the output result of railway object intrusion, overcoming the deficiency of poor real-time performance due to non-maximum value suppression operation with anchor frame detection, and it reduced calculation load and speeded up the detection efficiency. The experimental results show that the lightweight model has higher detection accuracy, and the size of the model is reduced by 179.01 MB after the improvement. The detection rate is increased to 39 frames/s, which is 3.9 times that of the YOLOv4 method. Compared with other detection methods, the proposed method can detect infrared railway object intrusion quickly and accurately.

Fatigue Properties and Life Prediction of Ultrasonic Rolling EA4T Axle Steel
ZHANG Jiwang, ZHANG Haonan, YANG Bing, SU Kaixin, LI Hang
2024, 59(6): 1305-1313.   doi: 10.3969/j.issn.0258-2724.20220257
[Abstract](300) [FullText HTML](101) PDF 2602KB(48)
Abstract:

In order to study the influence of surface ultrasonic rolling processing (SURP) on the fatigue properties of EA4T axle steel, the EA4T axle steel specimens were firstly treated by SURP technology, and the surface properties of the treated specimens were analyzed. The 3D surface morphologies, roughness, hardness, residual stress, full width at half maximum (FWHM), and crystal size were investigated. Then, the fatigue tests were carried out on the EA4T axle steel specimens using a rotary bending fatigue testing machine. The stress–fatigue life (S-N) curves and crack propagation behaviors were obtained, and the effect of SURP on fatigue properties and crack propagation behaviors of EA4T axle steels was analyzed. Finally, a back propagation (BP) neural network was used to establish the fatigue life prediction model of SURP EA4T axle steel, which took load stress amplitude, surface roughness, surface FWHM, surface hardness, hardened layer depth, surface residual stress, and depth of residual stress layer as input. In addition, the life of SURP EA4T axle steel specimens was predicted. The results show that SURP can reduce the surface roughness of the specimens to 0.17 μm and remove the groove morphology. Meanwhile, the surface hardness of the specimens is improved to 420 HV, and a surface residual stress of about −500 MPa and a residual stress layer with a depth of about 550 μm are introduced. There are conventional fatigue limits for grinding specimens, grinding with polishing specimens, as well as SURP specimens. The fatigue properties of grinding specimens and grinding with polishing specimens are basically the same, with a fatigue limit of 355 MPa. The fatigue property of SURP specimens is improved significantly, with a fatigue limit of 455 MPa, an increase of 28% compared with the grinding specimens. Fatigue fracture observations show that the fatigue cracks of all specimens initiate from the surface, and SURP cannot change the fatigue damage mechanism of the specimen. SURP can increase the threshold value of crack propagation of the specimen from 6.29 MPa·m1/2 to 11.21 MPa·m1/2, and it can slow down the crack initiation and propagation of short cracks, thus significantly improving the fatigue property of EA4T axle steel. The fatigue life prediction model of SURP EA4T axle steel has a prediction accuracy of 88.5%.

Short-Period Error Suppression Method of PCB-Based Inductive Linear Displacement Sensor
TANG Qifu, LI Mi, ZHAO Jing, GUO Yangting, PENG Song
2024, 59(6): 1314-1321.   doi: 10.3969/j.issn.0258-2724.20220450
[Abstract](208) [FullText HTML](77) PDF 2802KB(44)
Abstract:

In the linear displacement measurement, the printed circuit board (PCB)-based new inductive displacement sensors is easy to lead to short-period errors in manufacturing, assembly, and other process links because of its large pitch. Among the types of short-period errors caused, the first-order and fourth-order errors are the most common short-period errors in PCB-based inductive linear displacement sensors. Therefore, in order to reduce the first-order and fourth-order errors, the generation mechanism of these two kinds of errors was first studied from the output signals, and then an error self-correction method that did not depend on external reference was proposed. Firstly, the sources of short-period first-order and fourth-order errors and the functions of the two errors with the original sine (SIN) and cosine (COS) signals of the sensor were analyzed theoretically. Then, a short-period error function model based on the characteristics of the original SIN and COS signals of the sensor was established, and the corresponding parameters of the first-order and fourth-order errors in the error function model were calculated based on the measured data of the sensor prototype. Finally, the first-order and fourth-order error models were used for the error compensation of the sensor prototype. The results of prototype experiments show that the peak-to-peak value of the error after compensation is reduced from 51.6 μm to 36.2 μm. The short-period first-order error is reduced by about 64.5%, and the short-period fourth-order error is reduced by about 83.0%.

Braking Energy Utilization in Urban Rail Transit: Status and Prospects
LIU Jizong, ZHANG Zutao, WANG Hao, KONG Lingji, YI Minyi, ZHU Zhongyin
2024, 59(6): 1322-1345.   doi: 10.3969/j.issn.0258-2724.20220676
[Abstract](449) [FullText HTML](404) PDF 4133KB(88)
Abstract:

The development of urban rail transit plays an important role in alleviating urban traffic congestion, and its regenerative braking energy utilization technology has attracted much attention. At present, the inverter regenerative braking energy utilization technology includes the topology structure of the feedback circuit, vehicle-network voltage relationship, and feedback device optimization. Other regenerative braking energy utilization technologies include various energy storage types such as supercapacitor energy storage, flywheel energy storage, and battery energy storage. On this basis, the regenerative braking energy utilization technology in urban rail transit based on inverter feedback and energy storage feedback was systematically and comprehensively reviewed, and the characteristics, trends, and key research issues in the development process of the technology were pointed out in terms of improving energy storage density, system stability, and device life, so as to provide guidance for further exploration and commercial development in this field. In addition, the research trends of regenerative braking energy utilization technology in urban rail transit were analyzed, and future research can focus on system topology optimization, energy storage capacity, system stability, service life, and technical and economic analysis.

Method of Splicing Constant Speed Signals with Short Signals During Wheelset Acceleration and Deceleration
ZHANG Wei, DONG Dawei, HUANG Yan, YAN Bing, HUA Chunrong, LYU Lumei, SONG Shizhe
2024, 59(6): 1346-1356.   doi: 10.3969/j.issn.0258-2724.20220523
[Abstract](162) [FullText HTML](95) PDF 4138KB(46)
Abstract:

The characteristic value of train wheelsets is closely related to the speed, and the quantitative analysis of wheelset faults requires signals with a certain length collected at a certain speed. However, such a signal is difficult to be obtained by the system working in the variable speed condition. Therefore, a signal reconstruction method that did not require any velocimeters was proposed to realize the above quantitative analysis. This method used short signal segments to splice the constant speed signals under the acceleration and deceleration conditions. Firstly, a short-time Fourier transform (STFT) peak search method was adopted to obtain the speed curve and extract multiple signal segments passing through a specified speed. Secondly, the signal segments were converted into an angular domain signal, and the phase difference between signals was determined by cross-power spectra density (CPSD). Then, according to the phase difference and the length of the front signal, the splicing position of signals was obtained, and interpolation and fusion techniques were used to ensure the continuity of spliced signals. Finally, the spliced angular domain signal was resampled into the time domain signal. A rotor test bench with a similar wheelset structure has verified that during acceleration and deceleration of a cracked shaft, the frequency spectrums of the spliced signals of each speed obtained by this method are highly close to the frequency spectrums of the constant speed signals obtained by the experiment. The relative errors of the 1x and 3x values between the spliced signal of 15.0 Hz and the constant speed signal are only 0.9% and 1.0%, respectively. After adding noise to the signals to be spliced and shortening them to 1.5 cycles, the splicing phase error does not exceed 10°.

Formation Mechanism of Metro Wheel Polygonal Based on Vehicle-Track Coupling
SHI Yixuan, DAI Huanyun, MAO Qingzhou, SHI Huailong, WANG Qunsheng
2024, 59(6): 1357-1367, 1388.   doi: 10.3969/j.issn.0258-2724.20220785
[Abstract](289) [FullText HTML](143) PDF 5666KB(67)
Abstract:

Wheel polygonal wear will deteriorate the vibration environment of rail vehicles, lead to resonance fatigue failure of structural components, and seriously threaten driving safety. To study the formation mechanism of wheel polygonal wear of metro vehicles, the dynamic line tracking test was carried out, and the vertical coupling finite element model and dynamics model of the track were established. In addition, the iterative simulation analysis of long-term wheel-track wear was carried out. The results show that the wheel polygonal wear of 7–9th order occurs in the measured vehicle, which leads to the forced vibration of 50–70 Hz, and the frequency is close to that of the P2 force during the coupling vibration of the wheel-track system. Through the iterative simulation analysis of wheel wear, it is determined that P2 force resonance of the wheel-rail system caused by periodic irregular rail joint weld is the root cause of the 7th–9th order wheel polygonal wear. Under the long-term action of P2 force, the floating slab track bed and the ladder sleeper track bed of steel spring will cause 8th and 15th order wheel polygonal wear, respectively.

Method for Compressing Departure Tracking Interval of High-Speed Trains Based on Pre-departure Strategy
LU Gongyuan, HU Liuyang, PENG Hui, ZHANG Hongxiang, ZHANG Shoushuai
2024, 59(6): 1368-1377.   doi: 10.3969/j.issn.0258-2724.20220064
[Abstract](113) [FullText HTML](36) PDF 2427KB(14)
Abstract:

The departure tracking interval is one of the main bottlenecks that limit the 3-minute tracking operation of trains, and compressing the departure tracking interval can effectively improve line capacity. The departure tracking process of high-speed trains was first analyzed, and a pre-departure annunciator was set at a certain distance inside the outbound annunciator, making the train have a certain initial speed and shortening the remaining outbound distance when the outbound annunciator was open. At the same time, the principle of “failure-oriented safety” for the pre-departure process was put forward to ensure that the train did not cross the outbound annunciator. Then, based on the analysis of factors affecting the compression of departure tracking interval, the curves of train control mode under different pre-departure schemes were studied. Finally, the high-speed yard of Shanghai Hongqiao Station was studied, and the results show that the departure tracking interval can be compressed by the proposed method. The compression effect increases first and then decreases with the increase in the pre-departure distance, and the maximum compressible departure tracking interval can be more than 26 s if the pre-departure distance reaches 200 m of the effective lengths of the arrival-departure track.

Hyperpath Searching Algorithm Method Based on Signal Delay at Intersections
DU Muqing, JU Ziyan, LI Dawei
2024, 59(6): 1378-1388.   doi: 10.3969/j.issn.0258-2724.20220387
[Abstract](143) [FullText HTML](40) PDF 2217KB(16)
Abstract:

The periodic change of intersection signals in urban road systems leads to the uncertain delay of vehicle travel. In order to reduce the delays of vehicles at signal-controlled intersections, an improved hyperpath searching algorithm was proposed with the minimization of travel time on the road segments and the expected delay at the intersections as the optimization goal. First, according to the probability distribution function of vehicles arriving at the intersection, the expected waiting time and the turning movement proportion were derived. Then, the high-performance hyperpath searching algorithm was developed with the introduction of the label setting algorithm. Finally, the improved hyperpath searching algorithm was applied to the road network at Xinjiekou area, Nanjing, and the optimal hyperpath set was used to evaluate the applicability of the algorithm. The results show that compared with the shortest path strategy, hyperpath searching algorithm reduces the intersection delay and the total travel time by 67.1% and 22.3%, respectively as drivers shift to a driving route in the optimal hyperpath set. Furthermore, the hyperpath-based strategy can optimize the trip distribution in the road network, alleviating traffic congestion and contributing to flow equilibrium.

Determination of Influence Range of Urban Traffic Congestion and Identification of Key Road Sections
ZHAO Xueting, HU Liwei, KOU Fangling
2024, 59(6): 1389-1397.   doi: 10.3969/j.issn.0258-2724.20220413
[Abstract](135) [FullText HTML](37) PDF 4679KB(35)
Abstract:

In order to determine the influence range of non-point source traffic congestion and identify key road sections, the risk field strength theory and the regional growth method were introduced to improve the plume model. The maximum and core influence ranges were determined, and key road sections were identified. First, the “source-path-sink” of non-point source traffic congestion was defined, and the “source” risk field strength model of non-point source traffic congestion was constructed based on the traffic survey data and traffic status data in Guiyang in 2021. By considering the traffic influence of different land use properties and the adjustment coefficient of different road grades for calibration, the identification model of the maximum influence range was established based on different “source” risks, and the regional growth method was introduced to establish a model for determining the influence range of the core area of the road section. Finally, based on the traffic volume, length, and time of the road section, the damage evaluation index of the road section with traffic congestion was constructed, and quantitative research on the degree of traffic congestion was carried out. The original model, the improved model, and the actual situation were compared. The results show that different land use properties and different road grades have different influences on traffic congestion in road sections. The improved identification model of influence range based on different “source” risks is more effective, and the prediction accuracy is increased by 3.54%, which is closer to the actual situation. With the regional growth method, the accuracy of the influence range of the core area of the road section with traffic congestion is higher, which is 2.66% different from the actual situation. In summary, a new idea for the delineation of the cumulative risk range of urban non-point source traffic congestion and the determination of key risk paths is provided, also serving as a theoretical basis for further governance of different types of traffic congestion.

Simulation Research on Coupling Relationship Between Energy Distribution and Dynamic Response of High-Speed Solenoid Valves
ZHAO Jianhui, CHEN Wenfei, YANG Guichun, CHEN Jingyan
2024, 59(6): 1398-1405.   doi: 10.3969/j.issn.0258-2724.20220452
[Abstract](377) [FullText HTML](72) PDF 2501KB(44)
Abstract:

In order to study the energy distribution inside the high-speed solenoid valve and the coupling relationship between the energy parameters and the dynamic response, the performance of the high-speed solenoid valve was optimized. Firstly, the dynamic model of the high-speed solenoid valve was established based on the finite element method, and the accuracy of the model was validated through the experimental data. Secondly, based on the D-optimal design of experiments and the method of least squares, the response surface prediction model of the solenoid valve’s dynamic response characteristics was constructed, with the energy parameters as the factors. Finally, based on the meta-analysis method, the simulation analysis of the dynamic response of the high-speed solenoid valve with significant energy parameters and parameter interactions was carried out. The results show that the eddy energy E1 is the relatively sensitive parameter affecting the response time of high-speed solenoid valve opening To among the single parameters, and To increases by about 25% with the increase in E1. The interaction between E1 and damping energy E3 and between E1 and Joule energy E4 is the highly sensitive parameter affecting To, and the interaction between E1 and E4 is the highly sensitive parameter affecting the response time of closing Tc. The results also find that the factors that play a dominant role in the interaction parameters change with the range of values.

Theoretical Study on Uplift Calculation of Embedded Twelve Ground Screws of Transmission Angle Steel Tower
HE Songyang, YAN Xiuqing, LI Zhengliang, LIU Xiangyun, LI Zhong, GONG Tao
2024, 59(6): 1406-1414.   doi: 10.3969/j.issn.0258-2724.20230011
[Abstract](83) [FullText HTML](40) PDF 3570KB(14)
Abstract:

In order to solve the problem of ground screw connection under large load of transmission angle steel tower, an embedded twelve ground screw joint structure was proposed. Based on the plastic yield line theory of stiffness difference evolution, the influence of the position of ground screws and the stiffness difference between ground screws and tower foot plates was considered, and the theoretical formula of uneven internal force between embedded ground screws and external ground screws under uplift load was derived. Then, combined with 24 sets of refined numerical analysis, the influence of different ground screw diameters, ground screw spacings, and tower foot plate thicknesses on the differences in uplift forces of internal and external ground screws was studied, and the correction coefficient of stiffness difference was calibrated. Finally, the theoretical formula was verified by 72 sets of numerical experiments. The research results show that the embedded twelve ground screw structure can improve the uplift bearing capacity of the joint by 40%–50% compared with the traditional eight ground screw structure; when the internal ground screw is arranged on the orthogonal line of the external ground screw, the uneven distribution coefficient of internal force of the internal and external ground screws under the uplift load is about 1.1, and it does not change with the diameter of the ground screw and the thickness of the tower foot plate. When the internal screw is close to the external screw along the diagonal, the uneven distribution coefficient of the internal force of the internal screw will decrease, but when the thickness of the tower foot plate increases, the uneven distribution coefficient will increase. The calculation results based on the plastic yield line theory of stiffness difference evolution of the tower foot plate are compared with the numerical simulation results. The average value of the ratio of the theoretical uneven distribution coefficient to the numerical uneven distribution coefficient is 1.01, and the coefficient of variation is 0.03.

Wind-Induced Vibration of 400 km/h Trains with Vertical Sound Barrier on Highspeed Railway Bridge
LI Xiaozhen, ZHANG Xiaobang, ZHENG Jing, XU Hong, CHEN Feng
2024, 59(6): 1415-1422.   doi: 10.3969/j.issn.0258-2724.20220033
[Abstract](258) [FullText HTML](149) PDF 1990KB(68)
Abstract:

The increasing speed of high-speed trains makes the dynamic problem of sound barriers prominent. In this study, the dynamic amplification factor of vertical sound barriers caused by high-speed trains was taken as the research object to explore the vibration characteristics and influencing parameters of vertical sound barriers. Firstly, the finite element model of the vertical sound barrier on a high-speed railway bridge was established, and its basic dynamic characteristics were analyzed. Then, the vibration law of the sound barrier under the fluctuating wind load of 400 km/h train was studied, and the dynamic amplification factor of the sound barrier steel structure was calculated based on it. Finally, the vibration response and dynamic amplification factor of the sound barrier were analyzed with multiple parameters. The results show that the dynamic amplification factor of the sound barrier column with a height of 5.0 m is about 2.76 when the train’s speed is 400 km/h. The distance between the installed sound barrier and the center line of the track is increased from 3.8 m to 4.7 m, and the dynamic amplification factor of the bending moment response is reduced by 0.3. The dynamic magnification factors of the bending moment responses of sound barrier columns with a height of 2.3, 3.3, and 5.0 m are 1.64, 2.52, and 2.76, respectively. The transverse displacement of the top is increased from 0.45 mm to 3.80 mm, while the bending moment of the bottom is increased by 26.8% and 60.8%, respectively. Increasing the height of the sound barrier is not conducive to the vibration characteristics of the structure.

Line Shape of Boundary Transition Section of Terrain Model at Bridge Sites in Complex Mountainous Areas
ZHANG Mingjin, YAN Tingyuan, HU Bo, CHEN Hongyu, LI Yongle
2024, 59(6): 1423-1430.   doi: 10.3969/j.issn.0258-2724.20220282
[Abstract](184) [FullText HTML](90) PDF 2243KB(49)
Abstract:

The curve of the transition section of the terrain model at bridge sites in complex mountainous areas directly affects the accuracy of the wind tunnel experiment or numerical simulation results. To study the ideal form of line shape used in the boundary transition section of the terrain model at the bridge site, the principle of constructing line shape of the transition section was put forward based on the two ideas of setting up the transition section. The numerical simulation method was used to compare the three types of typical line shapes of the transition section in terms of the flow separation characteristics, mean wind speed profiles, wind attack angle profiles, and distribution of turbulent kinetic energy along the route under the uniform flow. The influence law of the slope change of the transition section on the flow field was also explored. The results show that the sine-squared curve exhibits superior characteristics compared with other line shapes, with a maximum shear stress difference of 3.77 × 10−3 Pa at the same location in terms of flow separation characteristics, a maximum wind speed difference of 0.09 m/s in terms of transitional performance of wind, and a maximum turbulent kinetic energy difference of 1.46 × 10−3 J. These findings provide important insights for selecting the line shape of the transition section of the terrain model at bridge sites.

Analysis of Bending Natural Vibration Characteristics of Box Girder Based on Additional Deflection for Shear Lag
ZHANG Yuyuan, ZHANG Yuanhai, ZHANG Hui
2024, 59(6): 1431-1439.   doi: 10.3969/j.issn.0258-2724.20220618
[Abstract](187) [FullText HTML](85) PDF 1897KB(47)
Abstract:

In order to reveal the influence of the bending space effect on natural vibration frequency weakening, the additional deflection caused by the shear lag effect was selected as the generalized displacement, and the warping additional deformation of box girder was incorporated into the total kinetic energy of the system. The bending variational solution of the natural vibration frequency of box girder considering the influence of shear deformation, shear lag, and their double effects was established by using the Hamilton principle. The difference ratio parameter of spatial effect on natural vibration frequency weakening was introduced, and the influence of the section size and the side-to-middle span on the difference ratio parameter was analyzed in detail. The example analysis shows that the analytical solution of the natural vibration frequency of the box girder considering shear derformation and double effects is in good agreement with the finite element numerical solution. A larger frequency order indicates a greater weakening degree of each effect to the natural vibration frequency. The double effect is the most significant, which reduces the natural vibration frequency of simply supported and continuous box girders by 4.72% and 4.80% respectively for the first-order frequency. The larger span width ratio, width-to-height ratio, and side-to-middle span ratio indicate a smaller difference ratio of natural vibration frequency. A larger plate width ratio is accompanied by a smaller difference ratio of natural vibration frequency considering shear lag and double effect and a larger difference ratio of natural vibration frequency considering shear derformation . At the same span width ratio, shear lag and shear derformation effects weaken the natural vibration frequency to the same extent. At the different width-to-height ratio ratios, the shear lag effect weakens the natural vibration frequency to almost the same extent, and the shear derformation effect has a more significant impact. Low-order natural vibration frequency can be calculated using a box girder without a cantilever plate.

Optimization Analysis and Monitoring of Construction Process of Open Spherical Reticulated Shell Structure with a Large Rise-to-Span Ratio
SHI Kairong, LIN Zhiyi, JIANG Zhengrong, CHEN Chunguang, CHEN Yiqiao, LIANG Jun
2024, 59(6): 1440-1447, 1486.   doi: 10.3969/j.issn.0258-2724.20220228
[Abstract](162) [FullText HTML](81) PDF 2462KB(27)
Abstract:

To ensure the construction safety of the complex spatial grid structure, the optimization analysis and monitoring of the construction process were carried out. An open single-layer spherical reticulated shell structure with a large rise-to-span ratio was taken as an example, and the construction process of this complex special-shaped structure was simulated through finite element analysis (FEA). By changing the boundary conditions of the support, the shape of the rib axis, and the support mode of the temporary support jig frame, different FEA models were established. The stress variations of key members and the structural displacement were analyzed to optimize the construction process. On this basis, the arc rod model with a temporary support jig frame was used as the final calculation model for construction process simulation, and the calculation results before and after unloading were compared with the on-site monitoring data to verify the accuracy of the FEA model in simulating the construction process. The failure sensitivity of the temporary support jig frame was further studied to avoid structural safety problems. The results show that the FEA model is consistent with the actual structure. The stress of each measuring point before and after unloading changes slightly, and the maximum tensile and compressive stress changes are 10.61 MPa and −5.67 MPa, respectively. The special-shaped spherical reticulated shell with a large rise-to-span ratio is in a controllable state during construction. The failure of a certain temporary support jig frame would have a great influence on member stress and structural displacement in the adjacent area. The maximum change of the member stress is 28.00 MPa, and that of the vertical displacement is 13 mm. Therefore, the reliability of the support jig frame shall be ensured during the construction.

Experimental Study on Dam Foundation Leakage Detection by Magnetoelectric Method Based on M Sequence
LIU Jin, CHE Wenyue, QIAN Wei, ZHANG Huapeng, HUANG Guojiao, DING Liang, HE Xiufeng
2024, 59(6): 1448-1456.   doi: 10.3969/j.issn.0258-2724.20220681
[Abstract](120) [FullText HTML](59) PDF 2819KB(35)
Abstract:

The dam foundation leakage problem has been a key factor affecting the overall safety of reservoir dams. To effectively and accurately detect dam foundation leakage, the magnetoelectric method based on M sequence correlation identification technology was applied to the dam leakage detection based on the pseudo-random identification principle. Firstly, the distribution of magnetic induction intensity, mean square error, and variation coefficient under various leakage depth conditions were characterized through the analysis of physical model experiments. Then, various leakage forms, high-resistance shielding layers, and leakage channel numbers were designed, so as to obtain the response characteristics of the detection results to the inclined channel, high-resistance shielding layer, and multiple leakage channels. Finally, the field test of Hongshiyan Dam in Yunnan Province was conducted to study the feasibility of this technology. The results show that under different burial depth conditions, the variation coefficients of maximum magnetic induction intensity vary within 2%. Along the inclined leakage channel, the magnetic induction intensity decreases slowly, and the ridge direction of the magnetic field contour map can be considered as the inclined leakage direction. The magnetic induction intensity is affected by the high-resistance shielding layer and has an error between 10% and 20%. The multiple leakage channels can be reflected by the concentrative distribution of abnormal zones in magnetic field contour maps. The leakage directions are observed in the field test, containing NW300°, SW265°, W215°, and NW305°, respectively.

Characteristics and Significance of New Geological Tectonic Activities in Niba Mountain Fault Zone
DENG Ronggui, ZHONG Zhibin, WANG Wenpo, WANG Yuanyuan, ZHANG Jin, LIU Yuancheng
2024, 59(6): 1457-1468.   doi: 10.3969/j.issn.0258-2724.20220376
[Abstract](188) [FullText HTML](62) PDF 5310KB(39)
Abstract:

New geological phenomena have been found in the structural geological mapping of Niba Mountain tunnel field of Ya’an to Xichang section of Beijing−Kunming Expressway. To demonstrate the nature of the Niba Mountain fault zone and new tectonic phenomena of regional geological tectonic significance, using quartz particle morphology scan, geological mechanics and rockmass mechanics theory and numerical simulation analysis method, first elaborated the area of Niba Mountain tunnel engineering geological environment and the new tectonic phenomena, and then discusses the Niba Mountain fault zone boundary faults and tectonic activity, Secondly, the regional geological tectonic significance of the neotectonic phenomenon is discussed. Finally, the existence of the neotectonic phenomenon and the rationality of the evidence of the regional tectonic new framework are demonstrated by numerical simulation analysis. The results show that: 1) the Niba Mountain fault zone has obvious neotectonic activity characteristics; 2) the Niba Mountain fault zone to which the new tectonic deformation phenomenon belongs has genetic homology with the Xianshuihe active fault zone in the “Y” shaped active tectonic zone in western Sichuan, which is the southeast extension of the Xianshuihe fault zone; 3) the Niba Mountain fault zone and its southeastern extension fault (Ebian−Mabian−Leibo segment) and the “Y” shaped active tectonic zone in western Sichuan constitute the original “X” type tectonic model, and have the conditions for the breeding of moderate and strong earthquake activities.

Numerical Analysis of Multiphysics Coupling of Grout Penetration
CHEN Feng, YANG Jie, ZHANG Chong, YU Zhen, LIU Xianfeng
2024, 59(6): 1469-1478.   doi: 10.3969/j.issn.0258-2724.20220763
[Abstract](266) [FullText HTML](59) PDF 2804KB(40)
Abstract:

Grout penetration in the unsaturated formation is a complex multiphysics process. In order to analyze more accurately the penetration characteristics of grout in saturated and unsaturated formations and estimate the range of grout penetration and grout compaction area, a multiphysics coupling model for unsaturated porous media was developed based on mixture theory. A novel five-degree-of-freedom eight-node quadrilateral axisymmetric Serendipity element was constructed through the secondary development of ABAQUS, so as to realize the numerical solution of soil deformation, soil porosity, pore pressure, and grout concentration distribution during grouting. The state variables, such as soil saturation and permeability coefficient, were updated in real time. The effects of grout water-cement ratio, grouting pressure, initial dry density, and water content of soil on the grouting in silty sand were analyzed with a three-dimensional axisymmetric grouting example, and the fitting curves of horizontal and vertical diffusion distance of grout with the above factors were obtained. The results show that the range of grout penetration is most significantly influenced by the water-cement ratio, followed by the grouting pressure, and it is least influenced by the water content and dry density of soil; the range of grout penetration increases with the increase in the water-cement ratio, especially when the water-cement ratio is greater than 1.0; a compacted area will be formed around the grouting pipe, where the soil is simultaneously subject to the grouting pressure and pore pressure; with the increase in the distance from the grouting pipe, the porosity of the soil gradually decreases in the compacted area and gradually recovers outside the compacted area, while the compacted area increases with the increase in the grouting pressure. The research results can provide theoretical guidance for calculating the grouting reinforcement in the soil.

Consolidation Solution of Aquitard Induced by Dropping of Groundwater Table with Continuous Drainage Boundary
JIANG Liuhui, LI Chuanxun, WU Wenbing, MEI Guoxiong
2024, 59(6): 1479-1486.   doi: 10.3969/j.issn.0258-2724.20220473
[Abstract](204) [FullText HTML](86) PDF 2006KB(33)
Abstract:

In order to investigate the influence of the drainage boundary, which can better reflect the actual permeability, on the land subsidence caused by over-exploitation of groundwater, firstly, a one-dimensional consolidation model of aquitard caused by the dropping of groundwater table in phreatic aquifer with continuous drainage boundary was established by introducing the continuous drainage boundary, where the pore pressure decayed exponentially with time. Secondly, the general analytical solutions of the model and the analytical solutions of two special dewatering models for the instantaneous dropping of the groundwater table and the single-stage and constant-rate dropping of the groundwater table were obtained by using the method of separate variables. Then, the correctness of the analytical theory in this paper was preliminarily verified by the degeneracy of the analytical solutions under certain conditions. Finally, the single-stage and constant-rate dropping of the groundwater table was taken as an example, and the consolidation curves of the aquitard under different interface parameters B were calculated based on the analytical solutions. In addition, the influence of interface parameter B on the consolidation behaviors was analyzed emphatically. The results show that the maximum error rate is 13% by comparing the theoretically calculated settlement curve with the experimental settlement curve, which further indicates that the continuous drainage boundary is closer to the actual permeable boundary. Furthermore, larger interface parameter B indicates (better water permeability of the drainage boundary) a faster pore pressure dissipation rate, faster consolidation rate, and shorter consolidation time, but the final consolidation state is not affected.

Experimental Study on Long-Term Deformation Characteristics of Deep and Thick Fills in Giant Karst Cave
SU Rui, SU Qian, HE Chenfang, DONG Minqi, WANG Xun, ZHENG Yuchao
2024, 59(6): 1487-1496.   doi: 10.3969/j.issn.0258-2724.20220642
[Abstract](88) [FullText HTML](27) PDF 3652KB(21)
Abstract:

In order to explore the variation of settlement and stress of the karst cave backfill and natural accumulation layer at different depths, a giant karst cave backfill project in the Yujingshan tunnel of Chengdu—Guiyang railway was studied. A 1∶100 laboratory centrifugal model test was carried out to analyze the long-term deformation law of the inhomogeneous natural soft accumulation layer at the bottom of the karst cave, in which the river sand with a particle size of less than 2 mm was used to simulate the karst cave backfill, and the western Sichuan clay was used to simulate the soft soil layer at the bottom of the karst cave. The reliability of the laboratory test was verified by field monitoring results. The results show that the deformation of the karst cave backfill basically reaches a stable state within 1.5 years after the termination of construction, and the deformation is about 86.9% of the total settlement; the deformation of the soft soil layer is the main component of the soil deformation at the bottom of the tunnel, and its deformation accounts for about 87.5% of the total settlement. The settlement at the bottom of the tunnel is positively correlated with the thickness of the soft soil layer, and when the thickness of the soft soil layer is less than 12.5 cm, it has less influence on the settlement at the bottom of the tunnel. The difference in settlement deformation between the model test and the on-site monitoring is only 3.83%, indicating that the experiments conducted in this article can reflect the long-term deformation characteristics of the soil at the bottom of the tunnel.

Bending Properties of Polypropylene Fiber-Sulfoaluminate Cement-Based Repair Material Using Grey Relation Theory
CUI Sheng’ai, XIA Wei, XU Lilin, ZHANG Shuhao, LI Guhua
2024, 59(6): 1497-1504.   doi: 10.3969/j.issn.0258-2724.20220459
[Abstract](152) [FullText HTML](75) PDF 2039KB(40)
Abstract:

To improve the economic benefits of engineered cementitious composite (ECC) and control the repair cycle, the polypropylene fiber-sulfoaluminate cement-based (PP-SACC) repair materials were designed with polypropylene fiber featuring low cost and sulfoaluminate cement featuring fast hardening and early strength employed as the key components. The influence of water-binder ratio, fiber content, and aggregate size on the bending properties of the repair materials was explored. In addition, the grey relation model was used to comprehensively evaluate PP-SACC under all working conditions. The results indicate that the fiber content is the most important factor that affects the strength, toughness, and crack characteristics. The influence factors of fiber content on initial crack strength, toughness index, and average crack width are −0.68, 0.79, and −0.98, respectively. The aggregate size can significantly affect the crack characteristics. The influence factor of quartz sand size on the average crack width is −0.86. The water-binder ratio also greatly affects the strength and toughness, and a reasonable water-binder ratio is beneficial to leverage the bridging effect of the fiber. The PP-SACC repair material has excellent toughness and flexural hardening properties.