开挖卸荷的瞬态特性研究

RESEARCH ON TRANSIENT CHARACTERISTICS OF EXCAVATION UNLOADING

针对中、高地应力条件下的岩体爆破开挖,通过岩体开挖荷载释放过程的力学分析及卸荷持续时间的计算,提出并论证岩体开挖荷载的释放为瞬态卸荷的观点,认为在中、高地应力条件下,岩体开挖荷载的释放需要考虑荷载的瞬态特性及其动力效应。同时,对与分段微差爆破对应的分步开挖荷载、瞬态卸荷方式、开挖卸荷诱发围岩振动及节理岩体瞬态卸荷松动机制等关键问题进行讨论。最后,结合二滩和瀑布沟等高地应力地区水电站地下厂房开挖瞬态卸荷诱发围岩振动的实测资料及观察到的动力破坏现象,对所提出的观点进行例证。

On the basis of the analysis of process of excavation unloading and the calculation of its releasing duration, it is shown that the excavation unloading during rock blasting is a transient process under middle to high in-situ stress conditions. It is proposed that the transient characteristics of the excavation unloading and correspondingly induced dynamic responses of surrounding rock should be considered under middle to high in-situ stress conditions. Problems such as the determination of divisional excavation unloading corresponding to millisecond delay initiation, the path of transient releasing of excavation unloading, releasing of excavation unloading-induced vibration and the mechanism of dynamic loosening of jointed rock mass induced by the transient unloading of in-situ stress, etc. are also discussed. Finally, two historical cases of excavation unloading-induced vibration and dynamic failure of jointed rock mass in Pubugou and Ertan Hydropower stations are presented as verifications.