岩石类脆性材料动态压剪耦合特性研究

Dynamic coupled behavior of rock materials under combined compression and shear loading

岩石具有复杂的细微观结构,其宏观力学性能表现出明显的加载路径敏感性和应变率效应。应用基于改进的SHPB装置,对花岗岩、大理岩和砂岩等三类岩石进行了五种倾角的准静态和动态压剪联合加载实验,较系统地讨论了与岩石应力应变关系曲线的拟线性阶段的斜率、破坏强度等有关的加载路径敏感性和应变率效应。结果表明:岩石的法向模量、切向模量和破坏强度都有明显的压剪耦合效应(即加载路径敏感性)和应变率效应;比较而言,法向模量对剪切应力的依赖性强于剪切模量对法向应力的依赖性。基于Drucker-Prager(D-P)准则和考虑压剪耦合效应的修正的DP准则拟合岩石的动静态破坏面,拟合结果表明:岩石的内黏聚力有一定的应变率效应,内摩擦角的应变率效应不明显;修正的D-P准则可以描述压剪耦合效应。并探讨了大理岩的后继屈服面和岩石应力应变关系的描述问题。此研究提供了一种确定岩石动态强度参数的方法,表明进行压剪联合加载实验研究有助于揭示复杂应力状态下岩石的动静态力学性能。

Since rocks are of complex structures at the micro and meso scales,they exhibit obvious load-path dependency and strain rate effect.Employing the modified split Hopkinson pressure bar （SHPB）device,a series of experiments were conducted to investigate the mechanical behaviors of three kinds of rocks,e.g.granite,marble,and sandstone,under quasi-static and dynamic combined compression and shear loading with five oblique angles.The load-path dependency and strain rate effect related to the slopes on stress strain relationship curves at the quasi-linear loading stage and the strength of rocks were analyzed in detail.The results show that normal,shear modulus and failure strength of rocks exhibit obvious strain rate effect and certain coupled compression-shear effect,which is also known as path-load dependency.The dependence of shear stress on normal modulus is stronger than that of normal stress on shear modulus. The Drucker-Prager（D-P）criterion and the modified D-P criterion,which consider the coupled compression and shear effect,were employed to fit the quasi-static and dynamic failure surfaces.The results show that the inner cohesion of rock exhibit certain strain rate effect,but the inner friction angle takes on little strain rate effect.Further discussions focus on the subsequent yield surfaces of marble and the description of stress strain relationship of rocks under combined compression and shear loading.These investigations provide a powerful method to determine strength parameters of rock materials under dynamic loading,and it is helpful to use the combined compression and shear experiments to investigate quasi-static and dynamic behaviors of rocks under complicated stress states.