含水量对高含冰量冻结砂土屈服面的影响

Effect of water content on yield surface of ice-rich frozen silty sand

以往关于冻土屈服特性的研究很少考虑含水量的影响,但实际工程中经常遇到的是变含水量情况,因此本文通过-5.0℃条件下高含冰量冻结砂土的一系列三轴压缩试验,系统地研究了含水量对屈服特性的影响,并且由此建立了带有含水量参数的偏应力-剪应变增量型关系式。试验结果表明:随含水量的变化,应力-应变曲线类型有明显变化,即在不同的含水量区间,含水量对硬化规律有不同的影响特性,因此为了使屈服函数的形式更加简单和提高拟合准确度,对于屈服函数的具体形式应该根据塑性剪应变(硬化参数)和含水量不同区间进行分别确定;当塑性剪应变较小时(0.00%~1.00%),随含水量的增大,偏应力逐渐增加,而当塑性剪应变较大时(大于1.00%),随含水量的增大,偏应力有一个先减小后增大的变化过程,并且42.0%可以作为含水量转折点;通过分段硬化原则建立的带有含水量参数的屈服函数与偏应力-剪应变的增量型关系式的模拟值与试验点基本相吻合,这说明得到的屈服函数与偏应力-剪应变的增量型关系式可以用于不同含水量条件下屈服面和偏应力-剪应变曲线的预测。

Previous researches on yield properties of frozen soil rarely consider the change of water content.However,water content often changes in practical engineering.So a series of triaxial compressive tests are conducted on ice-rich frozen silty sands at-5.0℃to investigate systemically the effect of water content on yield properties and then to establish a relationship between deviatoric stress and shear strain with change of water content.The experimental results show that with water content changing,there are obvious changes in the stressstrain curves,which show that water content has different influence on hardening law in different ranges of water content.So the concrete form about yield function should be determined according to ranges of plastic shear strain(hardening parameter)and water content to make the yield function simple and accurate.When plastic shear strain is within1.00%,deviatoric stress always increases with water content.However,with water content increasing,deviatoric stress firstly decreases and then increases when plastic shear strain is beyond1.00%.And water content of42.0%can be regard as a turning point.The yield function and the increment type relation between deviatoric stress and shear strain have been established with change of water content by segmented hardening principle.The testing results show that experimental values are basically consistent with simulated values.So they can be used to predict yield-surfaces and deviatoric stress-shear strain curves at different water contents.