砂岩球体法向恢复系数实验研究

Normal restitution coefficient of sandstone spheres

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。本文中采用自行设计的碰撞实验装置和声频采样技术,测定了砂岩球体碰撞的法向恢复系数,研究了粒径、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。结果表明:砂岩球体法向恢复系数存在复杂的尺寸效应,恢复系数随粒径的增大先增大后减小;碰撞过程中存在的黏弹性耗能机理和弹塑性损伤耗能机理共同作用产生了复杂的尺寸效应;受砂岩非均质特性的作用,粒径较小时,恢复系数的速度效应较明显(随速度增大而增大),粒径较大时速度对恢复系数的影响消失;砂岩饱和使黏弹性耗能和弹塑性损伤耗能增加,使恢复系数比风干时低;等效弹性模量对恢复系数的影响较大,等效弹性模量越大,法向恢复系数越小。

The normal restitution coefficient （NRC） is a key parameter that determines the trajectory of the stone during a rockfall. In this study, using a test equipment and a sound-sampling technique developed by ourselves, we first measured the NRC of sandstone spheres and analyzed its influencing factors, i.e. the particle size, the impact velocity, the hydrous state and the elastic properties of the plate, and then we examined the size effect, the rate effect and the energy dissipation mechanism of the NRC. The results show that the NRC of sandstone spheres has a complex size effect which, with the increase of the size of sandstone spheres, at first increases and then decreases. The analysis shows that there exists two energy dissipation mechanisms, i.e. the viscoelastic dissipation and the elastoplastic damage dissipation, interacting with each other, which result in the complex size effect; that, due to the heterogeneity of sandstones, the velocity effect of the NRC is obvious when the diameter of the sandstone particle is small, while this effect is unobservahle when the diameter is over 5 cm; that, compared with the NRC of air-drying sandstones, the saturation can cause the viscoelastic dissipation and elastoplastic damage dissipation to increase; and that the equivalent elastic modulus has a great impact on the NRC, i.e. the greater the equivalent elastic modulus, the smaller the NRC.