循环冲击载荷作用下砂岩破坏模式及其机理

利用岩石动静组合加载SHPB试验装置对不同静载砂岩试件进行循环冲击试验,研究其破坏模式.在研究岩石试件界面摩擦力的基础上,对不同静载作用下岩石试件的应力状态进行分析.研究应力波斜入射到微裂纹时的作用效应,探索具有一定静载的岩石在循环冲击作用下的破裂机理.研究结果表明:对具有三轴静载的试件,应力波在其最大剪应力所在平面进行斜入射时优先破坏.在循环冲击载荷作用下,具有轴向静载的岩石在破坏过程中具有明显的端部效应,而没有轴向静载的岩石则没有端部效应；静载荷的组合形式对岩石在循环冲击作用时的破坏模式影响较大；无静载荷作用时,岩石在循环冲击时逐步破坏成几块,破裂面平行于纵向面,属于张应变破坏；只有轴向静载作用时,岩石试件第1次破坏形成共轭双曲线型破裂面,进而在入射界面处发生破坏,破坏都属于张剪破坏；具有三轴静载作用时,由于轴向静载的不同,岩石最终破坏成圆锥台、圆锥体和V型锥体,破坏属于拉剪破坏.

Failure modes and mechanisms of sandstone under cyclic impact loadings

Based on modified split Hopkinson pressure bar(SHPB),failure modes of sandstone with different static loads under cyclic impacts were studied by tests.On the basis of analysing the value and distributing rule of interface friction of rock specimen,stress state characteristics of specimen with different static loads were researched.The effect of stress wave inclined to micro-crack was studied.The failure mechanisms of sandstone coupled static and cyclic impacts loadings were analysed.The results show that the rock specimen is more likely to fail when the stress waves are inclined to maximum shear stress plane of a point with three-dimensionally stressed state.The failure modes of specimens with axial static loads have apparent end effect when subjected to cyclic impact loadings,and no end effect with no axial static loads.The combining forms of static loads have great influence on failure modes.Rock specimens without static loads subjected to cyclic impact loadings fragment into several pieces step by step,and the rupture plane parallels to longitudinal section of specimens,the lateral tensile strain results in failure.Rock specimens only with axial static load subjected to cyclic impact loadings rupture into the shape of conjugate hyperbolas on the first failure,and the follow-up failures occur at incident end-face,and all the failures are the results of lateral tensile strains and shear stresses.When rock specimens are subjected to three dimensional static loads,specimens under cyclic impact loadings rapture into circular cone frustum,circular cone and V-shaped cone as the axial static pressures increase,and tensile stress(reflected longitudinal wave) and shear stress(reflected transversal wave) result in these failure modes.