不同小主应力和负温条件下冻结粉质黏土平面应变试验研究

Experimental study on plane strain of frozen silty clay under different minor principal stresses and negative temperatures

针对冻结法施工中的平面应变问题,利用改进的安徽理工大学冻土真三轴仪进行平面应变试验,分析冻结粉质黏土在不同小主应力和负温条件下的强度和变形特性,建立基于Weibull分布和Drucker-Prager强度准则的冻结粉质黏土损伤本构模型。理论和试验结果表明:同一温度下,不同小主应力下的应力-应变曲线呈现不同程度的硬化特征。破坏强度随小主应力的增加表现出先增后减的规律,随温度的降低呈线性增长的趋势。建立的非线性莫尔-库仑强度准则可以近似描述冻结粉质黏土的强度随小主应力增大而呈现出的非线性变化特征。不同试验条件下小主应力方向的应变均为膨胀变形,体应变均呈现剪缩的特性。随着小主应力的增大,试样的变形模量呈现先增后减的趋势;当小主应力相同时,其值随温度的降低而增大。当温度相同时,破坏时的中主应力随小主应力的增大同样表现出先增后减的趋势。建立的损伤本构模型可以较好地反映复杂应力路径下小主应力和温度对冻结粉质黏土强度和变形特性的影响。

Aiming at the plane strain problem in freezing method construction,the plane strain tests were carried out by using the improved true triaxial apparatus of frozen soil in Anhui University of Science and Technology.Subsequently,the strength and deformation of frozen silty clay were analyzed under different principal stresses and temperatures.Based on Weibull distribution and Drucker-Prager strength criterion,a damage constitutive model was established for frozen silty clay.The theoretical and experimental results demonstrate that the stress-strain curves under different minor principal stress exhibit different degrees of hardening characteristics at the same negative temperature.The failure strength increases first and then decreases with the increase of the minor principal stress,while it increases linearly with decreasing temperature.The established nonlinear Mohr-Coulomb strength criterion can describe the nonlinear correlation between the strength of frozen silty clay and the minor principal stress.Under different test conditions,the strain along the minor principal stress is expansion deformation,and the volume strain exhibits shear contraction.As the minor principal stress increases,the deformation modulus of the sample increases first and then decreases.For the same minor principal stress,the deformation modulus exhibits a negative correlation with temperature.Under the same temperature,the intermediate principal stress at failure also increases first and then decreases with increasing minor principal stress.The performed analysis revealed that the established damage constitutive model effectively considers the influence of minor principal stress and temperature on the strength and deformation of frozen silty clay under complex stresses.