砂土中松动土压力及松动区位移破坏形式的试验研究
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摘要
针对经典的Trapdoor问题,设计室内挡板下落模型试验装置,进行不同埋深比(埋深比为上覆土体高度与松动区宽度之比)的挡板下落模型试验,采用微型土压力盒量测试验全过程中挡板上方松动土压力的变化,对土体松动土压力及松动区位移破坏形式进行研究。将试验结果与文献既有解析解进行对比,进一步提出考虑挡板上土压力分布的修正松动土压力解析解。研究结果表明:由于土拱效应的存在,松动土压力小于土体自重土压力,松动土压力在试验初期迅速达到最小值,随后略有增长并达到稳定。利用颗粒图像测速技术研究松动区土体内部滑裂面发展规律,所得松动土压力与挡板上各位置松动土压力均吻合良好。松动区土体下移过程中均首先出现初始三角形滑裂面,随着松动区土体位移的增大,滑裂面发展呈现2种不同形式:当土体埋深比小于等于2时,呈逐渐张开展开形式;当土体埋深比大于2时,呈逐渐张开并塔型上升形式。
A trapdoor apparatus was designed to study the classic Trapdoor problem. Micro earth pressure cells were used to measure the loosening soil pressure on the trapdoor during whole period of tests. A series of trapdoor tests with different soil depth ratios(depth ratio is defined as the ratio of soil depth to trapdoor width) were conducted to analyze the loosening soil pressure and the failure mode of loosening zone. Tests results were compared with analytical solutions from literature and a modified analytical solution considering the stress distribution on trapdoor was proposed. The results show that because of soil arching effect, the loosening soil pressure is less than the soil weight. The loosening pressure quickly decreases to the minimum at initial stage of tests, then increases slightly and remains stable at last.Particle image velocimetry(PIV) method was used to analyze the development of slip surfaces in the loosening zone.Results calculated by proposed analytical solution fit well with the tests results. The initial slip surface is triangle slip surface. When the deformation of soil in loosening zone increases, there are two different forms of slip surfaces: it is called expansion form for condition that depth ratio is less than or equal to 2; or called expansion and tower raise form for condition that depth ratio is more than 2.
A trapdoor apparatus was designed to study the classic Trapdoor problem. Micro earth pressure cells were used to measure the loosening soil pressure on the trapdoor during whole period of tests. A series of trapdoor tests with different soil depth ratios(depth ratio is defined as the ratio of soil depth to trapdoor width) were conducted to analyze the loosening soil pressure and the failure mode of loosening zone. Tests results were compared with analytical solutions from literature and a modified analytical solution considering the stress distribution on trapdoor was proposed. The results show that because of soil arching effect, the loosening soil pressure is less than the soil weight. The loosening pressure quickly decreases to the minimum at initial stage of tests, then increases slightly and remains stable at last.Particle image velocimetry(PIV) method was used to analyze the development of slip surfaces in the loosening zone.Results calculated by proposed analytical solution fit well with the tests results. The initial slip surface is triangle slip surface. When the deformation of soil in loosening zone increases, there are two different forms of slip surfaces: it is called expansion form for condition that depth ratio is less than or equal to 2; or called expansion and tower raise form for condition that depth ratio is more than 2.
引文
[1]TERZAGHI K.Theoretical soil mechanics[M].New York:John Wiley and Sons Inc,1943:66-76.
[2]加瑞.盾构隧道垂直土压力松动效应的研究[D].南京:河海大学岩土工程研究所,2007:40-76.JIA Rui.Study on relaxation effect of vertical soil pressure for shield tunnel[D].Nanjing:Hohai University.Geotechnical Research Institute.2007:40-76.
[3]周小文,濮家骝,包承纲.隧洞拱冠砂土位移与破坏的离心模型试验研究[J].岩土力学,1999,20(2):32-36.ZHOU Xiaowen,PU Jialiu,BAO Chenggang.A study of the movement and failure characteristics of sand mass above the crown of a tunnel[J].Rock and Soil Mechanics,1999,20(2):32-36.
[4]DEWOOLKAR M M,SANTICHAIANANT K,KO H Y.Centrifuge modeling of granular soil response over active circular trapdoors[J].Soils and Foundations,2007,47(5):931-945.
[5]HAN J,WANG F,AL-NADDAF M,et al.Progressive development of two-dimensional soil arching with displacement[J].International Journal of Geomechanics,2017,17(12):04017112.
[6]IGLESIA G R,EINSTEIN H H,WHITMAN R V.Validation of centrifuge model scaling for soil systems via trapdoor tests[J].Journal of Geotechnical and Geoenvironmental Engineering,2011,137(11):1075-1089.
[7]IGLESIA G R,EINSTEIN H H,WHITMAN R V.Investigation of soil arching with centrifuge tests[J].Journal of Geotechnical and Geoenvironmental Engineering,2013,140(2):04013005.
[8]LADANYI B,HOYAUX B.A study of the trap-door problem in a granular mass[J].Canadian Geotechnical Journal,1969,6(1):1-14.
[9]ENGESSER F.über den Erddruck gegen innere Stützw?nde[J].Deutsche Bauzeitung,1882,16(1):91-96.ENGESSER F.About the earth pressure against inner supporting walls[J].German Construction,1882,16(1):91-96.
[10]MARSTON A.The theory of external loads on closed conduits in the light of the latest experiments[C]//Proc 9th Annual Meeting of the Highway Research Board.Washington DC:Highway Research Board,1930:138-170.
[11]EVANS C H.An examination of arching in granular soils[D].MA,USA:Massachusetts Institute of Technology,1983:20-58.
[12]陈若曦,朱斌,陈云敏,等.基于主应力轴旋转理论的修正Terzaghi松动土压力[J].岩土力学,2010,31(5):1402-1406.CHEN Ruoxi,ZHU Bin,CHEN Yunmin,et al.Modified Terzaghi loozening earth pressure based on theory of main stress axes rotation[J].Rock and Soil Mechanics,2010,31(5):1402-1406.
[13]蔺港,孔令刚,詹良通,等.基于太沙基土拱效应考虑基质吸力影响的松动土压力计算模型[J].岩土力学,2015,36(7):2095-2104.LIN Gang,KONG Linggang,ZHAN Liangtong,et al.An analytical model for loosening earth pressure considering matric suction based on Terzaghi soil arch effect[J].Rock and Soil Mechanics,2015,36(7):2095-2104.
[14]PAIKOWSKY S G,TIEN H S.Experimental examination of the arching mechanism on the micro level[C]//Discrete Element Methods:Numerical Modeling of Discontinua.Santa Fe,New Mexico,USA:American Society of Civil Engineers,2002:222-228.
[15]CHEVALIER B,OTANI J.Arching observation in threedimensional trapdoor problem with x-ray CT and discrete element method[J].Soils and foundations,2011,51(3):459-469.
[16]PARDO G S,SáEZ E.Experimental and numerical study of arching soil effect in coarse sand[J].Computers and Geotechnics,2014,57:75-84.
[17]STANIER S A,BLABER J,TAKE W A,et al.Improved image-based deformation measurement for geotechnical applications[J].Canadian Geotechnical Journal,2015,53(5):727-739.
[18]SZAJNA W S.Numerical modelling of soil arching in a shallow backfill layer[J].Civil and Environmental Engineering Reports,2014,15(4):127-137.
[19]KRYNINE D P.Discussion:stability and stiffness of cellular cofferdams by Karl Terzaghi[J].Trans ASCE,1945,110:1175-1178.
[20]彭述权,周健,樊玲,等.考虑土拱效应刚性挡墙土压力研究[J].岩土力学,2008,29(10):2701-2707.PENG Shuquan,ZHOU jian,FAN Ling,et al.Research on earth pressure of rigid retaining wall considering soil arching[J].Rock and Soil Mechanics,2008,29(10):2701-2707.
[21]王立国,王志凯.考虑土拱效应的挡土墙被动土压力分析[J].水利与建筑工程学报,2010,8(4):146-149.WANG Liguo,WANG Zhikai.Analysis on passive earth pressure for retaining walls considering soil arching[J].Journal of Water Resources and Architectural Engineering,2010,8(4):146-149.
[2]加瑞.盾构隧道垂直土压力松动效应的研究[D].南京:河海大学岩土工程研究所,2007:40-76.JIA Rui.Study on relaxation effect of vertical soil pressure for shield tunnel[D].Nanjing:Hohai University.Geotechnical Research Institute.2007:40-76.
[3]周小文,濮家骝,包承纲.隧洞拱冠砂土位移与破坏的离心模型试验研究[J].岩土力学,1999,20(2):32-36.ZHOU Xiaowen,PU Jialiu,BAO Chenggang.A study of the movement and failure characteristics of sand mass above the crown of a tunnel[J].Rock and Soil Mechanics,1999,20(2):32-36.
[4]DEWOOLKAR M M,SANTICHAIANANT K,KO H Y.Centrifuge modeling of granular soil response over active circular trapdoors[J].Soils and Foundations,2007,47(5):931-945.
[5]HAN J,WANG F,AL-NADDAF M,et al.Progressive development of two-dimensional soil arching with displacement[J].International Journal of Geomechanics,2017,17(12):04017112.
[6]IGLESIA G R,EINSTEIN H H,WHITMAN R V.Validation of centrifuge model scaling for soil systems via trapdoor tests[J].Journal of Geotechnical and Geoenvironmental Engineering,2011,137(11):1075-1089.
[7]IGLESIA G R,EINSTEIN H H,WHITMAN R V.Investigation of soil arching with centrifuge tests[J].Journal of Geotechnical and Geoenvironmental Engineering,2013,140(2):04013005.
[8]LADANYI B,HOYAUX B.A study of the trap-door problem in a granular mass[J].Canadian Geotechnical Journal,1969,6(1):1-14.
[9]ENGESSER F.über den Erddruck gegen innere Stützw?nde[J].Deutsche Bauzeitung,1882,16(1):91-96.ENGESSER F.About the earth pressure against inner supporting walls[J].German Construction,1882,16(1):91-96.
[10]MARSTON A.The theory of external loads on closed conduits in the light of the latest experiments[C]//Proc 9th Annual Meeting of the Highway Research Board.Washington DC:Highway Research Board,1930:138-170.
[11]EVANS C H.An examination of arching in granular soils[D].MA,USA:Massachusetts Institute of Technology,1983:20-58.
[12]陈若曦,朱斌,陈云敏,等.基于主应力轴旋转理论的修正Terzaghi松动土压力[J].岩土力学,2010,31(5):1402-1406.CHEN Ruoxi,ZHU Bin,CHEN Yunmin,et al.Modified Terzaghi loozening earth pressure based on theory of main stress axes rotation[J].Rock and Soil Mechanics,2010,31(5):1402-1406.
[13]蔺港,孔令刚,詹良通,等.基于太沙基土拱效应考虑基质吸力影响的松动土压力计算模型[J].岩土力学,2015,36(7):2095-2104.LIN Gang,KONG Linggang,ZHAN Liangtong,et al.An analytical model for loosening earth pressure considering matric suction based on Terzaghi soil arch effect[J].Rock and Soil Mechanics,2015,36(7):2095-2104.
[14]PAIKOWSKY S G,TIEN H S.Experimental examination of the arching mechanism on the micro level[C]//Discrete Element Methods:Numerical Modeling of Discontinua.Santa Fe,New Mexico,USA:American Society of Civil Engineers,2002:222-228.
[15]CHEVALIER B,OTANI J.Arching observation in threedimensional trapdoor problem with x-ray CT and discrete element method[J].Soils and foundations,2011,51(3):459-469.
[16]PARDO G S,SáEZ E.Experimental and numerical study of arching soil effect in coarse sand[J].Computers and Geotechnics,2014,57:75-84.
[17]STANIER S A,BLABER J,TAKE W A,et al.Improved image-based deformation measurement for geotechnical applications[J].Canadian Geotechnical Journal,2015,53(5):727-739.
[18]SZAJNA W S.Numerical modelling of soil arching in a shallow backfill layer[J].Civil and Environmental Engineering Reports,2014,15(4):127-137.
[19]KRYNINE D P.Discussion:stability and stiffness of cellular cofferdams by Karl Terzaghi[J].Trans ASCE,1945,110:1175-1178.
[20]彭述权,周健,樊玲,等.考虑土拱效应刚性挡墙土压力研究[J].岩土力学,2008,29(10):2701-2707.PENG Shuquan,ZHOU jian,FAN Ling,et al.Research on earth pressure of rigid retaining wall considering soil arching[J].Rock and Soil Mechanics,2008,29(10):2701-2707.
[21]王立国,王志凯.考虑土拱效应的挡土墙被动土压力分析[J].水利与建筑工程学报,2010,8(4):146-149.WANG Liguo,WANG Zhikai.Analysis on passive earth pressure for retaining walls considering soil arching[J].Journal of Water Resources and Architectural Engineering,2010,8(4):146-149.
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