Characteristics Analysis of Soil Arching Effect Behind Pile Based on Transparent Soil Technology
-
摘要: 为研究圆桩后土拱效应的特征及演化过程,从细观角度开展了基于透明土技术的桩土相互作用试验研究. 首先开展了透明土配比试验,获取物理力学性质适宜的土体;其次设计了试验系统并得到透明土与桩相互作用的散斑场图像;最后通过particle image velocimetry (PIV)技术分析得到位移矢量图,进一步分析得到透明土位移变化规律. 研究结果表明:通过位移矢量图可以得到圆桩作用下土体运动趋势及土颗粒的位移特征,并可进一步解译得到位移等值线构成的拱形结构,即桩后土拱结构,呈现出抛物线形,其范围与桩径、桩间距及深度有相关性;桩径越大,土拱区域越大,桩径30 mm时,土拱高达100 mm,桩土相互作用的影响范围越大;桩间距越大拱高最大值越大,桩间距80 mm时,土拱高也达100 mm;不同深度下土拱拱高在变化趋势上有较大的相似性,深度越深,土拱的最大拱高越小,深度50 mm时,拱高60 mm;通过拟合公式得到,土拱最大拱高沿桩身方向从桩顶至桩底呈逐渐减小趋势,同时随土体位移增加,表现出先增大,后趋于一稳定值的特征,其稳定值的大小与桩径呈正相关、桩间距呈正相关及深度呈负相关.Abstract: In order to study the characteristics and evolution process of soil arching effect behind a circular pile, an experimental study on pile-soil interaction based on the transparent soil technology was carried out from a microscopic perspective. Firstly, the tests as to transparent soil ratio were carried out to obtain the soil with desirable physical and mechanical properties. Secondly, the experimental system was designed and the speckle field image of the interaction between the transparent soil and pile was obtained. Finally, the displacement vector diagram was obtained through particle image velocimetry (PIV) technique, and the displacement variation rule of the transparent soil was further analyzed. The results show that the movement trend and displacement characteristics of soil particles under the action of the circular pile can be obtained through displacement vector, and the arch structure formed by displacement contour, namely, the soil arch structure behind the pile, can be further interpreted, as it presents a parabolic shape and its range is related to pile diameter, pile spacing and depth. The larger the pile diameter is, the larger the soil arch area is. When the pile diameter is 30 mm, the soil arch is up to 100 mm. Meanwhile, the pile-soil interaction affects larger region. The larger the pile spacing is, the larger the maximum arch height is. When the pile spacing is 80 mm, the soil arch height also reaches 100 mm. The soil arch height under different depths shows a similar trend. The deeper the depth is, the smaller the maximum arch height is. When the depth is 50 mm, the arch height is 60 mm. According to the fitting formula, the maximum arch height decreases gradually from the pile top to the bottom along the pile, and at the same time, it increases at first and then tends to stabilize with the increase of soil displacement. The stable value is correlated positively with pile diameter and pile spacing and negatively with depth.
-
Key words:
- circular anti-slide pile /
- transparent soil /
- model test /
- soil arching effect /
- arch height
-
表 1 透明土合成材料折射率
Table 1. Refractive index of transparent earth composite
材料 折射率 熔融石英砂 (SiO2) 1.458 3 正十二烷 (C12H26) 1.442 0 食品级15号白油 1.465 0 表 2 混合液配比表
Table 2. Mixed liquid ratios
正十二烷/ml 15号白油/ml 体积比 混合液折射率 8 92 1.0∶11.5 1.463 1 20 80 1.0∶4.0 1.460 5 24 76 1.0∶3.2 1.459 5 28 72 1.0∶2.5 1.458 5 30 70 1.0∶2.3 1.458 0 表 3 不同相对密度下透明土物理参数
Table 3. Physical parameters of transparent soil with different relative densities
相对密度 Dr/% 孔隙比 干密度/(g•cm−3) 试样质量/g 85 0.630 1.381 82.73 60 0.723 1.312 78.63 35 0.816 1.238 74.21 表 4 不同桩径试验参数
Table 4. Test parameters with different pile diameters
mm 桩径 桩间距 层面深度 桩长 10 60 10 160 20 60 10 160 30 60 10 160 表 5 不同桩间距试验参数
Table 5. Test parameters with different pile spacing
mm 桩径 桩间距 层面深度 桩长 20 40 10 160 20 60 10 160 20 80 10 160 表 6 不同深度试验参数
Table 6. Test parameters with different depths
mm 桩径 桩间距 层面深度 桩长 20 60 10 160 20 60 30 160 20 60 50 160 -
TERZAGHI K. Stress distribution in dry and in saturated sand above a yielding trap-door[C]//Procee-dings of 1st Conference of Soil Mechanics and Foundation Engineering. Boston: Cambridge Press, 1936: 307-316 CHEN L T, POULOS H G, HULL T S. Model tests on pile groups subjected to lateral soil movement[J]. Soils and Foundations, 1997, 37(1): 1-12. doi: 10.3208/sandf.37.1 张建勋,陈福全,简洪钰. 被动桩中土拱效应问题的数值分析[J]. 岩土力学,2004,25(2): 174-178. doi: 10.3969/j.issn.1000-7598.2004.02.002ZHANG Jianxun, CHEN Fuquan, JIAN Hongyu. Numerical analysis of soil arching effects in passive piles[J]. Rock and Soil mechanics, 2004, 25(2): 174-178. doi: 10.3969/j.issn.1000-7598.2004.02.002 张建华,谢强,张照秀. 抗滑桩结构的土拱效应及其数值模拟[J]. 岩石力学与工程学报,2004,23(4): 699-699. doi: 10.3321/j.issn:1000-6915.2004.04.032ZHANG Jianhua, XIE Qiang, ZHANG Zhaoxiu. Arching effect of anti-slide pile structure and its numerical simulation[J]. Chinese Journal of Rock Mechanics and Engineering, 2004, 23(4): 699-699. doi: 10.3321/j.issn:1000-6915.2004.04.032 韩爱民,肖军华,梅国雄. 被动桩中土拱效应特征与影响参数研究[J]. 工程地质学报,2006,14(1): 111-116. doi: 10.3969/j.issn.1004-9665.2006.01.021HAN Aimin, XIAO Junhua, MEI Guoxiong. Behavior of soil arching between passive pilesand effects parameters study[J]. Journal of Engineering Geology, 2006, 14(1): 111-116. doi: 10.3969/j.issn.1004-9665.2006.01.021 周应华,周德培,冯君. 推力桩桩间土拱几何力学特性及桩间距的确定[J]. 岩土力学,2006,27(3): 455-457. doi: 10.3969/j.issn.1000-7598.2006.03.023ZHOU Yinghua, ZHOU Depei, FENG Jun. Geometrically mechanical characters of soil arch between two adjacent laterally loaded piles and determination of suitable pile spacing[J]. Rock and Soil mechanics, 2006, 27(3): 455-457. doi: 10.3969/j.issn.1000-7598.2006.03.023 刘飞成, 张建经, 闫世杰, 等. 基于桩网路堤简化分析方法的参数研究[J]. 西南交通大学学报, 2018, 53(6): 1227-1236.LIU Feicheng, ZHANG Jianjing, YAN Shijie, et al. Parameters analysis based on simplified method to solve piled embankment with geogrid-reinforcement[J]. Journal of Southwest Jiaotong University, 2018, 53(6): 1227-1236. MANNHEIMER R J, OSWALD C J. Development of transparent porous media with permeabilities and porosities comparable to soils,aquifers,and petroleum reservoirs[J]. Ground Water, 1993, 31(5): 781-788. doi: 10.1111/j.1745-6584.1993.tb00851.x ISKANDER M, SADEK S, LIU J. Optical measurement of deformation using transparent silica gel to model sand[J]. International Journal of Physical Modelling Geotechnics, 2002, 2(4): 13-26. doi: 10.1680/ijpmg.2002.020402 孔纲强,孙学谨,肖扬,等. 透明土与标准砂压缩变形特性对比试验研究[J]. 岩土工程学报,2016,38(10): 1895-1903. doi: 10.11779/CJGE201610020KONG Gangqiang, SUN Xuejin, XIAO Yang, et al. Comparative experiments on compressive deformation properties of transparent soil and standard sand[J]. Chinese Journal of Geotechnical Engineering, 2016, 38(10): 1895-1903. doi: 10.11779/CJGE201610020 ISKANDER M G, LIU J, SADEK S. Transparent amorphous silica to model clay[J]. Journal of Geotechnical & Geoenvironmental Engineering, 2002, 128(3): 262-273. WILLERT C. The fully digital evaluation of photographic PIV recordings[J]. Applied Scientific Research, 1996, 56(2/3): 79-102. doi: 10.1007/BF02249375 LIU J. Visualization of 3-D deformations using transparent “soil” models[D]. New York: Polytechnic University, 2003. 曹兆虎,孔纲强,刘汉龙,等. 基于透明土的管桩贯入特性模型试验研究[J]. 岩土工程学报,2014,36(8): 1564-1568. doi: 10.11779/CJGE201408025CAO Zhaohu, KONG Gangqiang, LIU Hanlong, et al. Model tests on pipe pile penetration by using transparent soils[J]. Chinese Journal of Geotechnical Engineering, 2014, 36(8): 1564-1568. doi: 10.11779/CJGE201408025 周航,孔纲强,崔允亮. 基于透明土的XCC桩沉桩挤土效应模型试验及其理论研究[J]. 土木工程学报,2017,50(7): 100-109.ZHOU Hang, KONG Gangqiang, CUI Yunliang. Model test and theoretical study on XCC pile penetration effect based on transparent soil[J]. China Civil Engineering Journal, 2017, 50(7): 100-109. 齐昌广,左殿军,刘干斌,等. 塑料套管混凝土桩挤土效应的非侵入可视化研究[J]. 岩石力学与工程学报,2017,36(9): 2334-2340.QI Changguang, ZUO Dianjun, LIU ganbin, et al. Non-intrusively visualization on squeezing effect of plastic tube cast-in-place concrete piles[J]. Chinese Journal of Rock Mechanics and Engineering, 2017, 36(9): 2334-2340. 周东,刘汉龙,仉文岗,等. 被动桩侧土体位移场的透明土模型试验[J]. 岩土力学,2019,40(7): 2686-2694.ZHOU Dong, LIU Hanglong, ZHANG Wengang, et al. Transparent soil model test on the displacement field of soil around single passive pile[J]. Rock and Soil Mechanics, 2019, 40(7): 2686-2694. KONG G Q, CAO Z H, ZHOU H, et al. Analysis of piles under oblique pullout load using transparent-soil models[J]. Geotechnical Testing Journal, 2015, 38(5): 728-736. LIU J Y, ISKANDER M G. Modeling capacity of transparent soil[J]. Canadian Geotechnical Journal, 2010, 47(4): 451-460. doi: 10.1139/T09-116 谭可源. 刚性桩复合地基土拱效应的研究[C]//中国公路学会第七届中国公路科技创新高层论坛. 北京: 人民交通出版社, 2015: 112-120.