冻融循环作用后饱和黏土的应变速率效应试验研究

Experimental investigation on strain rate effects of saturated clay subjected to freeze-thaw cycles

为研究不同应变速率加载对融化饱和黏土力学效应的影响,对不同初始压实度的融化饱和黏土进行了不同应变速率和围压下的固结不排水三轴剪切试验,分析了融化饱和黏土的应力-应变关系曲线特征、孔隙水压力、割线模量(E_(50))、峰值强度、残余强度、抗剪强度指标的变化规律。结果表明:随着应变速率的增大,融化饱和黏土峰值强度和残余强度均先增大后减小,随后持续增大;而E_(50)模量则一直增大。应变速率未改变偏应力峰值所对应的应变大小;初始压实度不影响融化饱和黏土峰值强度对应的应变值,且在围压为120 k Pa、应变速率为0.15%/h时初始压实度对融化饱和黏土孔隙水压力发展趋势的影响不大,而当应变速率超过1.5%/h时,初始压实度的影响显著。随着围压增大,融化饱和黏土峰值强度对应的应变值及孔隙水压力明显增大。应变速率小于15%/h时,内摩擦角随着应变速率增大而减小,应变速率大于15%/h时,内摩擦角则随着应变速率增大而增大;黏聚力随着应变速率的增大持续增大。其研究结果对加深融土应变速率效应的理解具有一定的理论意义。

Consolidated undrained triaxial shear tests on thawed saturated clay with different initial compaction degrees were conducted under different strain rates and confining pressures to study the effect of strain rates on the mechanical properties of the thawed saturated clay. The stress-strain characteristic curve, pore water pressure, secant modulus （E50）, peak strength, residual strength and shear strength index of thawed saturated clay were analyzed. The results show that when the strain rate increases, the peak and residual strengths of the saturated clay first increase then decrease, then continue to increase; but the secant modulus E50 increases continuously. The strain rate does not change the strain magnitude corresponding to the deviatoric stress peak. The initial compaction does not affect the strain value corresponding to the peak strength of the thawed saturated clay. And the initial compaction degree has little effect on the development trend of pore water pressure of thawed saturated clay at confining pressure of 120 kPa and strain rate of 0.15% / h. The effect of initial compaction is significant as the strain rate exceeds 1.5% / h. The confining pressures have great impact on the developments of the pore water pressures and the strain values at the peak strengths. With the increase of confining pressure, the strain value and the pore water pressure corresponding to the peak strength of the thawed saturated clay increase. Internal fraction angles decrease with the increase of strain rates when the strain rates slower than 15%/h, but increase with the increasing strain rates when the strain rates exceed 15%/h. Cohesion of the thawed saturated clay increases with the increase of strain rates. The results of this study imply theoretical significance to understand the effect of increasing the strain rate of molten soil.