斜椭圆应力路径下饱和松砂动力特性试验研究
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摘要
利用空心圆柱扭剪仪模拟斜入射地震波作用形成的斜椭圆应力路径,对比研究了等向固结条件下饱和福建标准松砂在循环斜椭圆、圆形、扭剪、三轴路径下的动力特性。试验研究表明:土体循环孔压发展存在陡升型和陡降型两种模式;圆形路径下累积孔压增长速率最快,循环扭剪最小;归一化孔压与斜椭圆的倾角无关,但受斜椭圆长短轴比及动应力比影响。砂土的不排水动强度与动应力路径密切相关,循环扭剪和循环三轴最大,循环斜椭圆次之,圆形路径最小。地震波从特定角度入射时,形成近似圆形路径,若只将地震波视为垂直入射的S波,将高估地基土体抗液化强度。
A set of tests with the hollow cylinder apparatus are conducted to simulate the oblique incident seismic waves. Tests are performed with two cyclic stress components involving the horizontal shear stress(torsional shear stress) and the vertical shear stress(stress difference between vertical normal stress and horizontal normal stress) to show an elliptical shape in the orthogonal coordinates of stress difference and shear stress. Then the dynamic characteristics of saturated Fujian standard loose sand, consolidated under isotropic undrained condition and applied with cyclic oblique elliptic stress path, cyclic circular shear, cyclic torsional shear and cyclic triaxial path, are studied. The experiment results show that the development of elastic pore pressure can be classified as "sharp dropping type" and "sharp rising type". The cumulative rates of excess pore water pressure under cyclic circular shear and under cyclic torsional shear are the fastest and the slowest respectively. The normalizing pore pressure is independent of inclination angle of the obliquity of elliptic path, but depends on the ellipticity of cyclic stress path and stress amplitude CSR. Experimental results also indicate that undrained dynamic strength of Fujian sand is closely related to cyclic stress path. The cyclic torsional shearing path and cyclic triaxial path have the highest dynamic strength. The strengths under standard inclined elliptical loading path and under cyclic circular path are lower and the lowest respectively. Approximate circular path can be generated with seismic wave in a particular incident angle. If seismic wave is regarded as vertical incident S wave, the soil liquefaction strength would be overestimated.
A set of tests with the hollow cylinder apparatus are conducted to simulate the oblique incident seismic waves. Tests are performed with two cyclic stress components involving the horizontal shear stress(torsional shear stress) and the vertical shear stress(stress difference between vertical normal stress and horizontal normal stress) to show an elliptical shape in the orthogonal coordinates of stress difference and shear stress. Then the dynamic characteristics of saturated Fujian standard loose sand, consolidated under isotropic undrained condition and applied with cyclic oblique elliptic stress path, cyclic circular shear, cyclic torsional shear and cyclic triaxial path, are studied. The experiment results show that the development of elastic pore pressure can be classified as "sharp dropping type" and "sharp rising type". The cumulative rates of excess pore water pressure under cyclic circular shear and under cyclic torsional shear are the fastest and the slowest respectively. The normalizing pore pressure is independent of inclination angle of the obliquity of elliptic path, but depends on the ellipticity of cyclic stress path and stress amplitude CSR. Experimental results also indicate that undrained dynamic strength of Fujian sand is closely related to cyclic stress path. The cyclic torsional shearing path and cyclic triaxial path have the highest dynamic strength. The strengths under standard inclined elliptical loading path and under cyclic circular path are lower and the lowest respectively. Approximate circular path can be generated with seismic wave in a particular incident angle. If seismic wave is regarded as vertical incident S wave, the soil liquefaction strength would be overestimated.
引文
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[12]黄博,丁浩,陈云敏.GDS空心圆柱仪动力试验能力探讨[J].岩土力学,2010,31(2):314-320.HUANG Bo,DING Hao,CHEN Yun-min.Preliminarystudy of dynamic testing performance of hollow cylinderapparatus[J].Rock and Soil Mechanics,2010,31(2):314-320.
[13]ISHIHARA K,TOWHATA I.Sand response to cyclicrotation of principal stress directions induced by waveloads[J].Soils and Foundations,1983,23(4):11-16.
[14]HIGHT D W,GENS A,SYMES M J.The development ofa new hollow cylinder apparatus for investigating theeffects of principal stress rotation in soils[J].Géotechnique,1983,33(44):355-383.
[15]SEED H B,LEE K L.Liquefaction of saturated sandduring cyclic loading[J].Journal of the Soil Mechanicsand Foundation Division,ASCE,1966,92(6):105-134.
[16]邵生俊,谢定义.饱和砂土的物态变化与孔隙水压力的关系[C]//第五届全国土动力学学术会议论文集.大连:[出版者不祥],1998:88-97.
[17]BOULANGER R W,SEED R B.Liquefaction of sandunder bi-directional monotonic and cyclic loading[J].Journal of Geotechnical Engineering,ASCE,1995,121(12):870-878.
[2]TAKAHIRO S,KAZUHIKO K,et al.Estimation ofearthquake motion incident angle at rock site[C]//Proceedings of 12th World Conference on EarthquakeEngineering.[S.l.]:[s.n.],2000,0956.
[3]潘旦光,楼梦麟,董聪.P、SV波作用下层状土层随机波动分析[J].工程力学,2006,23(2):66-71.PAN Dan-guang,LOU Meng-lin,DONG Cong.Randomwave-theory analysis of layered soil sites under P-andSV-wave excitations[J].Engineering Mechanics,2006,23(2):66-71.
[4]李山有,马强,韦庆海.地震体波斜入射下的断层台阶地震反应分析[J].地震研究,2005,28(3):277-281.LI Shan-you,MA Qiang,WEI Qing-hai.Seismic responseanalysis of fault step subjected to obliquely incident bodywaves[J].Journal of Seismological Research,2005,28(3):277-281.
[5]黄博,凌道盛,丁浩,等.斜入射地震波在土体中产生的动应力路径及试验模拟[J].岩土工程学报,2013,35(2):276-283.HUANG Bo,LING Dao-sheng,DING Hao,et al.Seismicstress path induced by obliquely incident waves and itssimulation[J].Chinese Journal of GeotechnicalEngineering,2013,35(2):276-283.
[6]栾茂田,金丹,许成顺,等.双向耦合剪切条件下饱和松砂的液化特性试验研究[J].岩土工程学报,2008,30(6):790-794.LUAN Mao-tian,JIN Dan,XU Cheng-shun,et al.Liquefaction of sand under bi-directional cyclic loading[J].Chinese Journal of Geotechnical Engineering,2008,30(6):790-794.
[7]栾茂田,金丹,张振东,等.饱和松砂的双向耦合剪切特性试验研究[J].岩土工程学报,2009,31(3):319-325.LUAN Mao-tian,JIN Dan,ZHANG Zhen-dong,et al.Liquefaction of sand under bi-directional cyclic loading[J].Chinese Journal of Geotechnical Engineering,2009,31(3):319-325.
[8]潘华,陈国兴,刘汉龙.变幅波浪荷载下饱和南京细砂残余孔隙水压力特性[J].岩石力学与工程学报,2011,30(4):843-849.PAN Hua,CHEN Guo-xing,LIU Han-long.Residualpore water pressure properties of Nanjing’s saturated finesand under wave loads with variable amplitudes[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(4):843-849.下转第170页
[9]谷川,蔡袁强,王军.地震P波和S波耦合的变围压动三轴试验模拟[J].岩土工程学报,2012,34(10):1903-1909.GU Chuan,CAI Yuan-qiang,WANG Jun.Couplingeffects of P-waves and S-waves based on cyclic triaxialtests with cyclic confining pressure[J].Chinese Journalof Geotechnical Engineering,2012,34(10):1903-1909.
[10]陶明安,沈扬,王鑫,等.空心圆柱仪模拟列车荷载下土中应力路径能力分析[J].岩土力学,2013,34(11):3166-3172.TAO Ming-an,SHEN Yang,WANG Xin,et al.Abilityanalysis of HCA to imitate stress path of soil caused bytrain load[J].Rock and Soil Mechanics,2013,34(11):3166-3172.
[11]钱建固,王永刚,张甲峰,等.交通动载下饱和软黏土累计变形的不排水循环扭剪试验[J].岩土工程学报,2013,35(10):1790-1798.QIAN Jian-gu,WANG Yong-gang,ZHANG Jia-feng,et al.Undrained cyclic torsion shear tests on permanentdeformation responses of soft saturated clay to trafficloadings[J].Chinese Journal of GeotechnicalEngineering,2013,35(10):1790-1798.
[12]黄博,丁浩,陈云敏.GDS空心圆柱仪动力试验能力探讨[J].岩土力学,2010,31(2):314-320.HUANG Bo,DING Hao,CHEN Yun-min.Preliminarystudy of dynamic testing performance of hollow cylinderapparatus[J].Rock and Soil Mechanics,2010,31(2):314-320.
[13]ISHIHARA K,TOWHATA I.Sand response to cyclicrotation of principal stress directions induced by waveloads[J].Soils and Foundations,1983,23(4):11-16.
[14]HIGHT D W,GENS A,SYMES M J.The development ofa new hollow cylinder apparatus for investigating theeffects of principal stress rotation in soils[J].Géotechnique,1983,33(44):355-383.
[15]SEED H B,LEE K L.Liquefaction of saturated sandduring cyclic loading[J].Journal of the Soil Mechanicsand Foundation Division,ASCE,1966,92(6):105-134.
[16]邵生俊,谢定义.饱和砂土的物态变化与孔隙水压力的关系[C]//第五届全国土动力学学术会议论文集.大连:[出版者不祥],1998:88-97.
[17]BOULANGER R W,SEED R B.Liquefaction of sandunder bi-directional monotonic and cyclic loading[J].Journal of Geotechnical Engineering,ASCE,1995,121(12):870-878.
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