往复剪切作用下砂泥岩混合料力学特性分析

土体在往复剪切作用下的力学性质对研究周期性荷载响应有重要意义。通过改进往复剪切直剪仪，设定4种法向应力进行32次循环剪切，研究了砂泥岩混合料应力应变曲线性态、滞回圈面积和阻尼比变化规律；通过分析剪切刚度随法向应力及往复剪次数的分布规律，建立了砂泥岩混合料剪切刚度经验计算方法；概化了颗粒间接触模式，揭示了砂泥岩混合料强度与变形微观机制。试验结果与理论分析表明:应力应变曲线随法向应力增大由应变软化逐渐转为应变硬化；滞回圈面积随往复剪次数增大而逐渐减小，阻尼比随往复剪次数增加而缓慢增大，且与法向应力无关。初始剪切刚度随法向应力呈线性分布，归一化剪切刚度与往复剪次数呈对数函数关系，据此建立了考虑法向应力与往复剪次数的砂泥岩混合料剪切刚度经验计算方法。

Analysis of mechanical properties of sand shale mixture under reciprocating shear

The mechanical properties of soil under reciprocating shear are of great significance to the study of cyclic load response. By improving the reciprocating shear direct shear instrument, 4 normal stresses are set for 32 cycles of shear. The behavior of stress-strain curve and the law of hysteresis loop area and damping ratio are found out for sandstone-mudstone particle mixture. According to the distribution law of shear stiffness with normal stress and reciprocating shear frequency, an empirical calculation method for shear stiffness of sandstone-mudstone particle mixture is established. By generalizing the contact mode between particles, the micro mechanism of strength and deformation is revealed for sandstone-mudstone particle mixture. Experimental results and theoretical analysis show that the stress-strain curve gradually changes from strain softening to strain hardening as the normal stress increases. The area of the hysteresis loop gradually decreases with the increase of the number of reciprocating shears, and the damping ratio increases slowly with the increase of the number of reciprocating shears, and has nothing to do with the normal stress. The initial shear stiffness is linear with the normal stress, and the normalized shear stiffness has a logarithmic function relationship with the number of reciprocating shears. Based on this, an empirical calculation of the shear stiffness of the sand-shale mixture considering the normal stress and the number of reciprocating shears is established.