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法向恢复系数是岩崩块石运动分析的关键参数,其取值直接决定了块石的运动轨迹。为了严格测定花岗岩球砾碰撞的法向恢复系数,分析其影响因素,试验采用自行设计的碰撞试验装置和声频采样技术,精确测定花岗岩球砾碰撞的法向恢复系数,研究球砾大小、碰撞速度、含水状态和板的弹性特性4个因素对恢复系数的影响;并基于弹性接触理论推导出碰撞过程的最大接触应力P_(0,max)、碰撞起裂速度v_(ci)和碰撞损伤速度v_(cd),构造接触应力割线变化率k来描述碰撞过程的率相关,分析碰撞法向恢复系数的尺寸效应和速率效应,对碰撞过程耗能机制进行探讨。试验结果表明:花岗岩球砾法向恢复系数存在明显的尺寸效应,低速下更加显著;法向恢复系数的速率效应同样较明显,并且速率效应受球砾尺寸和板的弹性特性影响,呈现较强的相关性;球砾大小和速度相同时,等效弹性模量E*越大,法向恢复系数越小;含水状态对法向恢复系数影响不大。理论分析表明:P_(0,max)和k为控制法向恢复系数变化规律的内在因素;尺寸和速度均是通过改变P_(0,max)和k使法向恢复系数呈现复杂的尺寸效应和速率效应。
The normal recovery coefficient is the key parameter of the rock block rock movement analysis, the value of which directly determines the motion trajectory of the rock block. In order to strictly determine the normal recovery coefficient of granite boulder collision and analyze the influencing factors, the self-designed collision test device and acoustic sampling technique were used to determine the normal recovery coefficient of granite boulder collision accurately. The effects of the gravel size, collision velocity , Water content and elastic properties of the plate on the recovery coefficient. Based on the elastic contact theory, the maximum contact stress P_ (0, max), the collision initiation rate v_ (ci) and the collision damage velocity v_ (cd), the rate of change of secant of contact stress is constructed to describe the rate dependence of collision process, the size effect and rate effect of normal coefficient of recovery of collision are analyzed, and the energy dissipation mechanism of collision process is discussed. The experimental results show that there is obvious size effect on granite gravel recovery coefficient, which is more significant at low speed. The velocity effect of normal recovery coefficient is also obvious, and the rate effect is influenced by the size of boulder and the elastic characteristics of the plate . When the size and velocity of the gravel are the same, the larger the equivalent elastic modulus E * is, the smaller the normal recovery coefficient is. The water-containing state has little effect on the normal recovery coefficient. The theoretical analysis shows that: P_ (0, max) and k are the internal factors that control the variation law of the normal recovery coefficient; both the size and the velocity make the normal recovery coefficient show a complex size effect by changing P_ (0, max) Rate effect.