粗粒土应力-应变特征试验

Mechanical Study on the Coarse-grained Soil Using Laboratory Triaxial Shear Test

以地震灾区四川省北川县曲山镇粗粒土为研究对象,利用室内GDS静/动三轴剪切仪,以围压、剪切速率、初始围压时间为变量,探讨了不同试验条件下粗粒土的抗剪强度指标变化,分析了粗粒土力学剪切过程和变形破坏形态。试验结果表明:试样的应力-应变曲线均呈现应变硬化现象;围压、剪切速率、初始围压时间对土体的力学特性均有不同程度的影响,其中围压的影响最为明显;土体的黏聚力为20.99 kPa,内摩擦角为22.7°;试样在达到20%的应变时,未出现明显的破裂面,而是呈径向鼓状,外形匀称。研究成果对认识粗粒土变形破坏机理具有一定的意义,同时能够为合理选取室内三轴试验条件参数提供参考。

Taking the coarse-grained soil in the earthquake area as the research object and considering confining pressure, shear rates, consolidation time as test variables, stress-strain relationship and strength characteristics were studied. Using cohesion and friction angle to evaluate the soil strength, the change of shear strength were discussed under different experimental conditions, and mechanical shearing process and deformation shapes were analyzed. The results show that stress-strain curves present strain-hardening phenomenon, and the confining pressure is the most influential among the variables. The cohesion is 20.99 kPa and friction angle is 22.7°. When the soil strain reaches to 20% , there is no obvious failure surface, but presents radial barrel deformation and well-balanced outside form. The results can not only offer some theoretical guidance in understanding the coarse-grained soil deformation and failure mecha- nism, but also provide references to select the reasonable triaxial test parameters.