Extension Evaluation on Excavation Safety of Deep Foundation Pit in Sandy Cobble Stratum Based on Entropy Method
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摘要: 为客观评价富水砂卵石地层中深基坑开挖的安全稳定性,根据结构变形、受力、地下水以及周边环境等因素选取地面沉降、建筑物沉降、地下水位等8个评价指标进行开挖安全性评价,以成都某地铁车站深基坑工程为例,根据基坑开挖4个月内的实测数据,采用熵值法对所选评价指标进行赋权,基于物元理论与可拓集合的关联函数,建立深基坑开挖安全可拓评价模型,并将评价结果与模糊综合评判结果进行比较. 研究结果表明:熵值赋权计算中,混凝土支撑轴力、桩顶沉降和支护结构水平位移是本案例中最重要的三项指标,对安全评价影响最大;对地面沉降与管线沉降的可拓评价结果比模糊综合评判结果高一个等级,与实际监测数据的评判结果相符,有利于施工过程中对潜在风险的防控;基于熵值赋权的可拓评价模型能够对基坑开挖安全性进行单因素分析与综合分析,所构建的可拓评价模型可以在成都地区富水砂卵石地层基坑工程安全评价中推广使用.Abstract: In order to objectively evaluate the safety and stability of deep foundation pit excavation in watery sandy pebble stratum, eight evaluation indexes, such as ground settlement, building settlement and groundwater level, are selected to evaluate the excavation safety according to the structural deformation, stress, groundwater and surrounding environment. A deep foundation pit project of a metro station in Chengdu is used as an example, and according to the measured data within the four months of foundation pit excavation, the entropy method is employed to assign the selected evaluation indexes. Based on the correlation function between the matterelement theory and extension set, the extension evaluation model of excavation safety for the deep foundation pitis established. Comparing the evaluation results with those of fuzzy comprehensive evaluation, it is concludedthat the axial force of concrete support, pile top settlement and the horizontal displacement of support structure are the most important three indexes in the entropy weight calculation of this case, which have the greatest impact on the safety evaluation. For the safety evaluation of ground settlement and pipeline settlement, the extension evaluation result is one grade higher than the fuzzy comprehensive evaluation result, which is consistent with actual monitoring data and is conducive to the prevention and control of potential risks in the construction process. The extension evaluation model based on entropy weight can accurately improve the safety of the foundation pit excavation through single factor analysis and comprehensive analysis, and the extension evaluation model can be applied in the safety evaluation of foundation pits in watery sandy cobble strata in Chengdu.
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表 1 凤溪站深基坑监测数据
Table 1. Monitoring data of deep foundation pit at Fengxi station
序号 开挖深度/m c1/mm c2/mm c3/m c4/mm c5/mm c6/kN c7/mm c8/mm 1 1 −2.69 −2.62 13.00 3.9 −1.03 29.84 −4.12 −0.62 2 6 −4.02 −2.31 15.00 3.0 −0.81 48.06 −7.24 −6.98 3 9 −6.65 −2.43 19.40 3.8 −1.79 152.90 −10.33 −7.62 4 14 −8.27 −3.17 21.00 5.8 −2.88 181.39 −13.10 −10.34 5 18 −6.81 −6.39 23.10 6.9 −3.68 646.69 −12.28 −12.10 6 22 −8.31 −8.04 25.40 7.6 −4.73 200.69 −12.46 −12.58 7 26 −10.51 −5.40 27.78 8.9 −5.75 212.55 −14.08 −12.94 8 30 −13.15 −7.29 32.00 8.4 −5.70 222.25 −13.65 −14.50 9 32 −12.37 −6.91 33.55 4.3 −6.24 264.09 −12.84 −14.61 表 2 熵值赋权计算结果
Table 2. Results of the entropy weighting method
项目 ej gj wj c1 0.958 873 0.041 127 0.100 230 c2 0.953 535 0.046 465 0.113 240 c3 0.980 939 0.019 061 0.046 453 c4 0.970 981 0.029 019 0.070 722 c5 0.923 029 0.076 971 0.187 586 c6 0.879 137 0.120 863 0.294 555 c7 0.978 304 0.021 696 0.052 875 c8 0.944 878 0.055 122 0.134 338 表 3 凤溪站深基坑开挖安全性判别
Table 3. Excavating safety evaluation for deep foundation pit at Fengxi station
监测项目 安全性判别标准 判别内容 Ⅰ级 Ⅱ级 Ⅲ级 结构变形 ${F_1} = \dfrac{ { {\text{实测变形值} } } }{ { {\text{基坑开挖深度} } } }$ F1 > 0.012
F1 > 0.0070.004 ≤ F1 ≤ 0.012
0.002 ≤ F1 ≤ 0.007F1 < 0.004
F1 < 0.002支撑轴力 ${F_2} = \dfrac{ { {\text{容许轴力} } } }{ { {\text{实测轴力} } } }$ F2 < 0.8 0.8 ≤ F2 ≤ 1.0 F2 > 1.0 基底隆起 ${F_3} = \dfrac{ { {\text{实测变形值} } } }{ { {\text{基坑开挖深度} } } }$ F3 > 1.0 × 10−2
F3 > 0.5 × 10−2
F3 > 0.2 × 10−20.4 × 10−2 ≤ F3 ≤ 1.0 × 10−2
0.2 × 10−2 ≤ F3 ≤ 0.5 × 10−2
0.4 × 10−3 ≤ F3 ≤ 0.2 × 10−2F3 < 0.4 × 10−2
F3 < 0.2 × 10−2
F3 < 0.4 × 10−3沉降值 ${F_4} = \dfrac{ { {\text{实测沉降值} } } }{ { {\text{基坑开挖深度} } } }$ F4 > 1.2 × 10−2
F4 > 0.7 × 10−2
F4 > 0.2 × 10−20.4 × 10−2 ≤ F4 ≤ 1.2 × 10−2
0.2 × 10−2 ≤ F4 ≤ 0.7 × 10−2
0.4 × 10−3 ≤ F4 ≤ 0.2 × 10−2F4 < 0.4 × 10−2
F4 < 0.2 × 10−2
F4 < 0.4 × 10−3地下水位 ${F_5} = \dfrac{ { {\text{降水设计值} } } }{ { {\text{实测水位} } } }$ F5 < 0.8 0.8 ≤ F5 ≤ 1.2 F5 > 1.2 注:1. F1上行适用于基坑附近无建筑物或地下管线的情况,下行适用于基坑附近有建筑物或地下管线的情况;
2. F3、F4的上、中行与F1同,下行适用于对变形有特别严格要求的情况.表 4 各监测指标关联函数值
Table 4. Correlation function values of monitoring indexes
Ⅰ级 Ⅱ级 Ⅲ级 K11 = −0.7945 K21 = 0.0137 K31 = −0.0259 K12 = −0.8744 K22 = −0.3719 K32 = 0.7438 K13 = −0.1740 K23 = 0.9329 K33 = −0.1555 K14 = −0.9603 K24 = −0.8609 K34 = 0.2781 K15 = −0.9025 K25 = −0.5125 K35 = 0.9750 K16 = −0.3958 K26 = −0.3626 K36 = 0.6598 K17 = −0.7800 K27 = 0.0500 K37 = −0.0833 K18 = −0.9348 K28 = −0.7717 K38 = 0.4566 表 5 各特征指标安全等级
Table 5. Safety level of characteristic indexes
评价方法 c1 c2 c3 c4 c5 c6 c7 c8 基于熵值法的
可拓评价Ⅱ级 Ⅲ级 Ⅱ级 Ⅲ级 Ⅲ级 Ⅲ级 Ⅱ级 Ⅲ级 模糊综合
评判方法Ⅲ级 Ⅲ级 Ⅱ级 Ⅲ级 Ⅲ级 Ⅲ级 Ⅲ级 Ⅲ级 表 6 监测指标预警值与监测值
Table 6. Warning values and monitoring values of monitoring indexes
项目 预警要求 最大监测值 预警值/
mm变化速率/
(mm•d−1)监测值/
mm变化速率/
(mm•d−1)c1 22.40 ≥ 3.00 13.15 2.55 c2 16.00 ≥ 3.00 8.04 1.67 c3 1600 ≥ 500 1850 1052 c4 22.40 ≥ 3.00 8.90 1.60 c5 22.40 ≥ 3.00 6.24 1.35 c7 20.00 ≥ 4.00 14.08 2.43 c8 22.40 ≥ 3.00 14.61 1.39 注:变化速率通常取工况前3 d内的最大值. -
CHOI H H, CHO H N, SEO J W. Risk assessment methodology for underground construction projects[J]. Journal of Construction Engineering and Management, 2004, 130(2): 258-272. doi: 10.1061/(ASCE)0733-9364(2004)130:2(258) KEPAPTSOGLOU K, KARLAFTIS M G, GKOUNTIS J. A fuzzy AHP model for assessing the condition of metro stations[J]. KSCE Journal of Civil Engineering, 2013, 17(5): 1109-1116. doi: 10.1007/s12205-013-0411-0 邓祥辉,徐甜,龚珍,等. 基于模糊层次分析法的地铁深基坑施工风险评估[J]. 数学的实践与认识,2017,47(13): 136-142.DENG Xianghui, XU Tian, GONG Zhen, et al. Risk assessment of metro deep excavation pit in construction based on fuzzy analytical hierarchical process[J]. Mathematics in Practice and Theory, 2017, 47(13): 136-142. 郭健,钱劲斗,陈健,等. 地铁车站深基坑施工风险识别与评价[J]. 土木工程与管理学报,2017,34(5): 32-38. doi: 10.3969/j.issn.2095-0985.2017.05.006GUO Jian, QIAN Jingdou, CHEN Jian, et al. Risk identification and evaluation for foundation pit construction of subway station[J]. Journal of Civil Engineering and Management, 2017, 34(5): 32-38. doi: 10.3969/j.issn.2095-0985.2017.05.006 叶派平,李春芳. 基于模糊理论的地铁车站深基坑工程风险评价[J]. 公路,2018,63(5): 232-236. 李明, 吴波, 李春芳. 深基坑工程周边建筑物安全模糊综合评价[J]. 隧道建设(中英文), 2018, 38(增刊1): 58-66.LI Ming, WU Bo, LI Chunfang. Fuzzy comprehensive evaluation for safety of surrounding buildings of deep foundation pit[J]. Tunnel Construction, 2008, 38(S1): 58-66. 周勇,郑晓静,朱彦鹏,等. 基于FZZY-AHP评估模型的地铁车站施工风险分析[J]. 兰州理工大学学报,2008,44(4): 109-115. doi: 10.3969/j.issn.1673-5196.2008.04.027ZHOU Yong, ZHENG Xiaojing, ZHU Yanpeng, et al. Risk analysis of subway station construction based on FZZY-AHP assessment model[J]. Journal of Lanzhou University of Technology, 2008, 44(4): 109-115. doi: 10.3969/j.issn.1673-5196.2008.04.027 黄磊. 模糊数学评价方法在深基坑安全评价中的应用[J]. 人民珠江,2019,40(3): 153-159. doi: 10.3969/j.issn.1001-9235.2019.03.026HUANG Lei. Application of fuzzy mathematics evaluation method in safety evaluation of deep foundation pit[J]. People's Pearl River, 2019, 40(3): 153-159. doi: 10.3969/j.issn.1001-9235.2019.03.026 申建红,盖立庭,万索妮,等. 基于模糊集与改进证据理论的深基坑施工风险评价[J]. 土木工程与管理学报,2019,36(2): 28-34,41. doi: 10.3969/j.issn.2095-0985.2019.02.005SHEN Jianhong, GAI Liting, WAN Suoni, et al. Risk assessment of excavation construction based on fuzzy set and improved evidence theory[J]. Journal of Civil Engineering and Management, 2019, 36(2): 28-34,41. doi: 10.3969/j.issn.2095-0985.2019.02.005 王成汤,王浩,覃卫民,等. 基于多态模糊贝叶斯网络的地铁车站深基坑坍塌可能性评价[J]. 岩土力学,2020,41(5): 1670-1679,1689.WANG Chengtang, WANG Hao, QIN Weimin, et al. Evaluation of collapse possibility of deep foundation pits in metro stations based on multi-state fuzzy Bayesian networks[J]. Rock and Soil Mechanics, 2020, 41(5): 1670-1679,1689. 程敏,王倩露,林慧龙,等. 基于改进FMEA法的深基坑施工风险评价[J]. 土木工程与管理学报,2008,35(1): 54-59,72.CHENG Min, WANG Qianlu, LIN Huilong, et al. Risk assessment of deep foundation pit construction based on improved FMEA method[J]. Journal of Civil Engineering and Management, 2008, 35(1): 54-59,72. 李立云,刘政,王兆辉. 基于灰色关联模型的改进型层次分析法与基坑风险评价[J]. 北京工业大学学报,2008,44(6): 889-896.LI Liyun, LIU Zheng, WANG Zhaohui. Improved analytic hierarchy process based on grey correlation model and its application in pit risk engineering[J]. Journal of Beijing University of Technology, 2008, 44(6): 889-896. 李立云,梁湟琴,贾雷. 基于灰色关联模型改进型层次分析法的基坑降水风险评价[J]. 防灾科技学院学报,2019,21(1): 23-29.LI Liyun, LIANG Huanqin, JIA Lei. Risk analysis on pit dewatering by improved analytic hierarchy process based on gray correlationmodel[J]. Journal of Institute of Disaster and Prevention, 2019, 21(1): 23-29. 陈楠. 基于IOWA算子的地铁车站深基坑施工安全综合评价[J]. 隧道建设(中英文),2020,40(2): 202-208.CHEN Nan. Comprehensive evaluation of construction safety of deep foundation pit of metrostation based on IOWA operator[J]. Tunnel Construction, 2020, 40(2): 202-208. 魏丹. 基于故障树和层次分析法的地铁施工风险评价——以隧道竖井基坑围护结构失稳为例[J]. 安全与环境工程,2008,25(1): 100-104. doi: 10.3969/j.issn.1671-1556.2008.01.027WEI Dan. Risk assessment of subway construction based on fault tree analysis and analytical hierarchy process:a case study of destabilization of pit supporting structure of tunnel shaft[J]. Safety and Environmental Engineering, 2008, 25(1): 100-104. doi: 10.3969/j.issn.1671-1556.2008.01.027 唐建新,李欣怡. 基于模糊数学的地铁深基坑稳定性评价[J]. 安全与环境学报,2008,18(6): 2135-2140.TANG Jianxin, LI Xinyi. On the stability evaluation of the deep foundation pit based on the fuzzy mathematics theory[J]. Journal of Safety and Environment, 2008, 18(6): 2135-2140. 侯文丽,徐港. 基于AHP的地下工程基坑开挖风险评价——以杭州艮山东路地下管廊工程为例[J]. 智能城市,2019,5(3): 11-13. 宋博. DEA-BP神经网络下地铁车站深基坑施工安全评价[J]. 中国安全科学学报,2019,29(5): 91-96.SONG Bo. Safety evaluation for deep foundation pit construction in metro station based on DEA-BP neural network[J]. Chinese Journal of Safety Science, 2019, 29(5): 91-96. 王景春,张法. 基于熵权二维云模型的深基坑施工风险评价[J]. 安全与环境学报,2008,18(3): 849-853.WANG Jingchun, ZHANG Fa. Risk assessment of the deep foundation pit based on the entropy weight and 2-dimensional cloud model[J]. Journal of Safety and Environment, 2008, 18(3): 849-853. 吴丹红,张美霞,张汉斌,等. 基于可拓学的地铁车站深基坑施工安全评价[J]. 安全与环境学报,2019,19(3): 761-766.WU Danhong, ZHANG Meixia, ZHANG Hanbin, et al. On the safety evaluation for deep foundation pit of the subway stations based on extenics[J]. Journal of Safety and Environment, 2019, 19(3): 761-766. 叶义成, 柯丽华, 黄德育. 系统综合评价技术及其应用[M]. 北京: 冶金工业出版社, 2006. 魏新江, 邓志秋, 魏纲, 等. 可拓评价方法和熵值法相结合的基坑安全评价[J]. 岩土工程学报, 2008, 30(增刊1): 672-676.WEI Xinjiang, DENG Zhiqiu, WEI Gang, et al. Safety evaluation of foundation pits by extension assessment method combined with entropy law[J]. Chinese Journal of Geotechnical Engineering, 2008, 30(S1): 672-676. 沈世伟,许君臣,代树林,等. 基于熵值赋权法的节理岩体隧道爆破质量可拓学评价[J]. 土木工程学报,2013,46(12): 118-126.SHEN Shiwei, XU Junchen, DAI Shulin, et al. Extenics evaluation of joint rock tunnel blasting quality based on entropy weighting method[J]. China Civil Engineering Journal, 2013, 46(12): 118-126. 刘招伟, 赵运臣. 城市地下工程施工监测与信息反馈技术[M]. 北京: 科学出版社, 2006.
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