南京砂的稳态特征研究
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摘要
以南京砂的固结不排水试验为基础,对其稳态特征进行了研究。结果表明:在低围压下稳态线的曲线表达更符合实际情况,松散南京砂在低围压下广义剪应力终值接近于0而表现出不稳定;稳态是土体固有属性,稳态内摩擦角不仅可以通过稳定状态下ps?s–qs?s的关系得到,也可通过同一围压下不同密实度南京砂的有效应力路径末端拟合得到,本研究得到南京砂稳态内摩擦角为35.2°;峰值强度高估了流滑中土体的强度,土体实际发挥的是残余强度,研究中建立了南京砂峰值强度和残余强度的关系;脆性指数能较好地反映南京砂应变软化程度和流滑的可能性;孔隙比的微小变化可导致南京砂软化程度的较大变化。
The CU tests on the reconstituted samples of Nanjing sand are performed and the experimental results are analyzed based on the steady-state theory.The steady-state line under low confining pressure is a curve,which is suitable for the behaviors of loose Nanjing sand in tests.The ultimate deviatoric stress of loose Nanjing sand under lower confining pressure is close to 0 and the behaviors in tests are unsteady.The steady state is the inherent attribute of soils.The steady-state angle of internal friction,35.2°for Nanjing sand,is obtained not only by a fitting curve of,but also by the linear extremity of effective stress paths under different relative densities.The peak strength of sand is overvalued during the flow slide,and there is the residual strength.The relation between the peak strength and the residual strength is obtained.The strength reduction in the strain softening and flow slide of Nanjing sand is expressed in terms of a brittleness index.A smaller change can lead to the larger change of the strain softening of Nanjing sand to great extent.
The CU tests on the reconstituted samples of Nanjing sand are performed and the experimental results are analyzed based on the steady-state theory.The steady-state line under low confining pressure is a curve,which is suitable for the behaviors of loose Nanjing sand in tests.The ultimate deviatoric stress of loose Nanjing sand under lower confining pressure is close to 0 and the behaviors in tests are unsteady.The steady state is the inherent attribute of soils.The steady-state angle of internal friction,35.2°for Nanjing sand,is obtained not only by a fitting curve of,but also by the linear extremity of effective stress paths under different relative densities.The peak strength of sand is overvalued during the flow slide,and there is the residual strength.The relation between the peak strength and the residual strength is obtained.The strength reduction in the strain softening and flow slide of Nanjing sand is expressed in terms of a brittleness index.A smaller change can lead to the larger change of the strain softening of Nanjing sand to great extent.
引文
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[9]ISHIHARA K.Liquefaction and flow failure during earthquake[J].Géotechnique,1993,43(3):351-415.
[10]VERDUGO R.The critical state of sands:discussion[J].Géotechnique,1992,42(4):655-663.
[11]朱建群.含细粒砂土的强度特征与稳态性状研究[D].武汉:中国科学院武汉岩土力学研究所,2007.(ZHU Jian-qun.Strength properties and steady-state behavior of sandy soil[D].Wuhan:Institute of Rock&Soil Mechanics,Chinese Academy of Science,2007.(in Chinese))
[12]YAMAMURO J A,LADE P V.Steady-state concepts and static liquefaction of silty sand[J].Journal of Geotechnical and Geoenvironmental Engineering,1998,124(2):868-877.
[13]SLADEN J A,DHOLLANDER R D,KRAHN J.The liquefaction of sand,a collapse surface approach[J].Canadian Geotechnical Journal,1985,22(4):546-578.
[2]CASAGRANDE A.Liquefaction and cyclic deformation of sands:a critical review[C]//Proc of the Fifth Pan American Conf on Soil Mechanics and Foundations Engineering.Buens Aires:1975.
[3]CASTRO G.Liquefaction and cyclic mobility of saturated sand[J].Journal of the Geotechnical Engineering Division,ASCE,1975,101(GT6):551-569.
[4]POULOS S J.The steady state of deformation[J].J Geotech Engrg Div,ASCE,1981,107(GT5):553-561.
[5]LADE V P,YAMAMURO J A.Evaluation of static liquefaction potential of silty sand slopes[J].Canadian Geotechnical Journal,2011,48(2):247-264.
[6]魏松,朱俊高,王俊杰,等.砂土的稳态强度固结不排水三轴试验研究[J].岩石力学与工程学报,2005,24(22):4151-4157.(WEI Song,ZHU Jun-gao,WANG Jun-jie,et al.Consolidated-undrained triaxial tests study on steady state strength of sand[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(22):4151-4157.(in Chinese))
[7]张津生,彭芝平,周景星.三峡堰基淤砂的流滑特性和抗剪强度指标的选用[J].水利学报,1998(6):14-18.(ZHANG Jin-sheng,PENG Zhi-ping,ZHOU Jing-xing.Flow-sliding property of sand deposit in the cofferdam of the Three Gorges Project and the determination of its shear strength parameters[J].Journal of Hydraulic Engineering,1998(6):14-18.(in Chinese))
[8]黄永林.南京砂的液化与判别[J].世界地震工程,2001,17(1):69-74.(HUANG Yong-lin.Liquefaction of the Nanjing sand and its identification[J].World Information on Earthquake Engineering,2001,17(1):69-74.(in Chinese))
[9]ISHIHARA K.Liquefaction and flow failure during earthquake[J].Géotechnique,1993,43(3):351-415.
[10]VERDUGO R.The critical state of sands:discussion[J].Géotechnique,1992,42(4):655-663.
[11]朱建群.含细粒砂土的强度特征与稳态性状研究[D].武汉:中国科学院武汉岩土力学研究所,2007.(ZHU Jian-qun.Strength properties and steady-state behavior of sandy soil[D].Wuhan:Institute of Rock&Soil Mechanics,Chinese Academy of Science,2007.(in Chinese))
[12]YAMAMURO J A,LADE P V.Steady-state concepts and static liquefaction of silty sand[J].Journal of Geotechnical and Geoenvironmental Engineering,1998,124(2):868-877.
[13]SLADEN J A,DHOLLANDER R D,KRAHN J.The liquefaction of sand,a collapse surface approach[J].Canadian Geotechnical Journal,1985,22(4):546-578.
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