变围压条件下粉质黏土动孔压特性试验研究

Experimental study on dynamic pore pressure characteristics of silty clay subjected to variable confining pressure

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（rumaxN）和最小孔压比曲线（ruminN）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rumax的稳定值随着循环围压幅值的增大而增大,最小孔压比rumin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（rumaxN）and the minimum pore pressure ratio curves（ruminN）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 rumaxincreases with the increase of cyclic confining pressure amplitude,but stable value of rumin 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.