变围压条件下粉质黏土动孔压特性试验研究
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摘要
为研究变围压条件下粉质黏土的孔压发展规律及强度特性,利用GDS振动三轴试验系统开展了不排水和部分排水时粉质黏土变围压循环三轴试验,研究了变围压应力路径对粉质黏土动孔压变化的影响规律。结果表明:变围压条件下,粉质黏土孔压主要由弹性孔压和残余孔压两部分组成。不排水条件时,粉质黏土最大孔压比随应力路径斜率和循环动应力比增加而增大,最小孔压受循环围压影响较小;部分排水试验时,最大孔压比曲线(r_u~(max)~N)和最小孔压比曲线(r_u~(min)~N)表现为先升后降;当振动次数N>2500次后,孔压变化逐渐趋于平稳。最大(小)孔压比均随着循环动应力比的增大而增大,但循环围压幅值对孔压比的影响却不同。最大孔压比r_u~(max)的稳定值随着循环围压幅值的增大而增大,最小孔压比r_u~(min)的稳定值随着循环围压幅值的增大而减小。上述研究成果可为交通循环荷载作用下粉质黏土的强度特性理论研究提供科学依据,为地基灾变控制研究提供技术支撑。
In order to study the pore pressure development pattern and strength characteristics of silty clay subjected to variable confining pressure,using GDS three axis vibration experimental system,cyclic three shaft experiment was carried out for silty clay under condition of undrained and partial drainage to study the influence of variable confining pressure stress path on dynamic pore pressure variation of silty clay.Results show that under the condition of variable confining pressure,the pore pressure of silty clay mainly consists of two parts,that is the elastic pore pressure and residual pore pressure.In the case of undrained silty clay,the maximum pore pressure ratio increases with the increase of th stress path slope and cyclic dynamic stress ratio,and the minimum pore pressure is less affected by cyclic confining pressure.In the case of partially drained silty clay,the maximum pore pressure ratio curves(r_u~(max)~N)and the minimum pore pressure ratio curves(r_u~(min)~N)rises first and then falls.When virbation times N >2500,the pore pressure variation tends to be stable.The maximum(minimum)pore pressure ratio increases with the increase of cyclic dynamic stress ratio,but the influence of cyclic confining pressure amplitude on pore pressure ratio is different.Stable value of r_u~(max)increases with the increase of cyclic confining pressure amplitude,but stable value of r_u~(min) decreases with the increase of cyclic confining pressure amplitude.Above results may provide scientific evidence for the study of silty clay strength characteristics under traffic cyclic loading,and provide key technical support for study of ground catastrophic control.
In order to study the pore pressure development pattern and strength characteristics of silty clay subjected to variable confining pressure,using GDS three axis vibration experimental system,cyclic three shaft experiment was carried out for silty clay under condition of undrained and partial drainage to study the influence of variable confining pressure stress path on dynamic pore pressure variation of silty clay.Results show that under the condition of variable confining pressure,the pore pressure of silty clay mainly consists of two parts,that is the elastic pore pressure and residual pore pressure.In the case of undrained silty clay,the maximum pore pressure ratio increases with the increase of th stress path slope and cyclic dynamic stress ratio,and the minimum pore pressure is less affected by cyclic confining pressure.In the case of partially drained silty clay,the maximum pore pressure ratio curves(r_u~(max)~N)and the minimum pore pressure ratio curves(r_u~(min)~N)rises first and then falls.When virbation times N >2500,the pore pressure variation tends to be stable.The maximum(minimum)pore pressure ratio increases with the increase of cyclic dynamic stress ratio,but the influence of cyclic confining pressure amplitude on pore pressure ratio is different.Stable value of r_u~(max)increases with the increase of cyclic confining pressure amplitude,but stable value of r_u~(min) decreases with the increase of cyclic confining pressure amplitude.Above results may provide scientific evidence for the study of silty clay strength characteristics under traffic cyclic loading,and provide key technical support for study of ground catastrophic control.
引文
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[11]谷川,王军,蔡袁强,等.考虑变围压因素的饱和软黏土循环纯压动力特性试验研究[J].岩土工程学报,2013,35(7):1307-1315(GU Chuan,WANG Jun,CAI Yuanqiang,et al.Undrained dynamic behaviors of saturated clays under compressive stress paths considering cyclic confining pressure[J].Chinese Journal of Geotechnical Engineering,2013,35(7):1307-1315(in Chinese))
[12]Simonsen E,Isacsson U.Soil behavior during freezing and thawing using variable and constant confining pressure triaxial tests[J].Can Geotechnical,2001,38(4):863-875.
[2]Pyke R M,Seed H B,Chan C K.Settlement of sands under multidirectional shaking[J].Journal of Geotechnical Engineering Division,ASCE,1975,101(4):370-398.
[3]Seed H B,Pyke R M,Martin G R.Effect of multi-directional shaking on pore water development in sands[J].Journal of Geotechnical Engineering Division,ASCE,1978,104(1):27-44.
[4]Ishihara K,Yamazaki F.Cyclic simple shear tests on saturated sand in multi-directional loading[J].Soils and Foundations,1980,20(1):45-59.
[5]Wichtmann T,Niemunis A,Trianafyllidis T.On the influence of the polarization and the shape of thestrain loop on strain accumulation in sand under high-cyclic loading[J].Soil Dynamics and Earthquake Engineering,2007,27(1):14-28.
[6]Sivathayakan S,Vhid Y P.Influence of generalized initial state and principal stress rotation on the undrained response of sands[J].Canadian Geotechnical Journal,2002(39):63-76.
[7]陈存礼,谢定义,高鹏.球应力往返作用下饱和砂土变形特性的试验研究[J].岩石力学与工程学报,2005,24(3):513-520(CHEN Cunli,XIE Dingyi,GAO Peng.Testing study on deformation characteristics of sarurated sand under repeated spherical stress[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(3):513-520(in Chinese))
[8]Rascol E.Cyclic properties of sand:dynamic behavior for seismic applications[D].Lausanne:Swiss Federal Institute of Technology in Lausanne,2009.
[9]Grabe P J.Effects of principal stress rotation on permanent deformation in rail track foundations[J].Journal of Geotechnical and Geoenvironmental Engineering,2009,135(4):555-565.
[10]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 Yuanqiang,WANG Jun.Coupling effects of P-waves and S-waves based on cyclic triaxial tests with cyclic confining pressure[J].Chinese Journal of Geotechnical Engineering,2012,34(10):1903-1909(in Chinese))
[11]谷川,王军,蔡袁强,等.考虑变围压因素的饱和软黏土循环纯压动力特性试验研究[J].岩土工程学报,2013,35(7):1307-1315(GU Chuan,WANG Jun,CAI Yuanqiang,et al.Undrained dynamic behaviors of saturated clays under compressive stress paths considering cyclic confining pressure[J].Chinese Journal of Geotechnical Engineering,2013,35(7):1307-1315(in Chinese))
[12]Simonsen E,Isacsson U.Soil behavior during freezing and thawing using variable and constant confining pressure triaxial tests[J].Can Geotechnical,2001,38(4):863-875.