危岩破坏激振效应试验研究

危岩破坏瞬间存在能量突然释放问题,对相邻危岩体产生明显的激振作用,可采用激振加速度、峰值速度及激振位移表征。以坠落式危岩为例,进行危岩破坏激振效应模型试验,获得了13万多个危岩破坏激振加速度测试数据。试验结果表明,实验条件下危岩破坏激振作用持续时间30 ms左右,激振加速度、峰值速度及激振位移均是竖直方向大于水平方向,存在约2倍关系,竖向激振加速度最大可及48.7979 m/s²,竖向激振峰值速度达27.2 mm/s,竖向激振位移可及0.0560 mm。基于试验现象,分析了危岩破坏机理进一步研究中应高度重视的两个重要科学问题,即危岩破坏过程中主控结构面端部遵循纯拉状态→弱剪强拉状态→强剪弱拉状态→纯剪状态的演变规律,科学描述各阶段的力学演绎过程,危岩稳定性分析中应考虑危岩破坏激振效应,科学表征危岩破坏瞬间相邻危岩体的瞬时稳定性态。研究成果为进一步分析危岩破坏机制及致灾效应具有一定参考借鉴作用。

Experimental study on excitation effect for unstable rock

The unstable rock has a sudden falling feature, which is a dynamic process to release energy speedily, and will put an evident excitation effect on the rocks around it. The excitation effect can be expressed by the excitation acceleration, peak velocity and excitation displacement. Focusing on the falling unstable rock, an experimental model of excitation effect is proposed. More than 130 thousands acceleration test data are obtained. The test results show that the duration of excitation effect of unstable rock can last about 30 ms; and the values of the excitation acceleration, peak velocity and excitation displacement in vertical direction are about double times larger than the ones horizontal direction; and the excitation acceleration in vertical direction can reach 48.7979 m/s²; the peak velocity is 27.2 mm/s; and the excitation displacement can reach 0.0560 mm. Based on those experimental phenomena, two important issues which must be highlighted for the damage mechanism of unstable rock are analyzed. The first issue is that the stress on the end of dominant fissure in the damage process will evolve from pure tension state to weak shear-strong tension state to strong shear-weak tension state and pure shear state, and the other issue is to describe the mechanical evolution processes for various states, to consider the excitation effect on the damage process of unstable rock, and to analyze the stability of the rock around the damaging moment of the unstable rock. The results may provide a scientific basis for further studies on the collapse mechanism and disaster effect of unstable rock.