考虑温度与围压影响的冻结砂土非正交弹塑性本构模型

Non-orthogonal elastoplastic model for frozen sand incorporating effects of temperature and confining pressure

冻土的受力变形特性受温度与围压的影响显著。为描述温度的影响,通过建立冻土三向拉伸强度与温度的非线性关系,并采用平移变换的方法将其考虑到屈服函数中。为描述围压的影响,通过建立潜在强度衰减因子,并将其引入统一硬化参量中,发展得出了考虑围压影响的硬化参量。最终,基于非正交弹塑性模型框架,在平移变换应力空间内建立了能够考虑温度和围压影响的冻土非正交弹塑性本构模型。模型预测结果与冻结粉砂三轴压缩试验结果的对比表明,所建立模型能够模拟不同温度和围压下冻结砂土应力–应变关系。其不仅能够反映冻土峰值抗剪强度随温度降低而增大的温度效应,还能描述围压增大条件下应力应变曲线由剪胀与软化型逐渐转变为剪缩与硬化型的规律。

The mechanical properties of frozen soils are significantly affected by temperature and confining pressure.To characterize the effects of temperature,a nonlinear relationship between the three-dimensional tensile strength and the temperature is established,which is incorporated into the yield function based on the coordinate transformation method.To characterize the effects of confining pressure,a potential strength degradation factor is established,which is used to develop the hardening parameters that effectively account for the effects of the confining pressure.Finally,based on the framework of the non-orthogonal elastoplastic model,a non-orthogonal elastoplastic constitutive model for frozen soils that can consider the effects of temperature and confining pressure is developed in the coordinate transformation space.Comparisons between the model predictions and the triaxial compression test results of the frozen silty sand demonstrate that the developed constitutive model can simulate the stress-strain relationship of frozen silty sand under different temperatures and confining pressures.The developed constitutive model characterizes the temperature effects,i.e.,the increase in the peak shear strength with decreasing temperature,and the confining pressure effects,i.e.,the transition from shear dilation and softening to shear contraction and hardening as reflected by the stress-strain curve under the increasing confining pressure.