深切河谷岩体结构的表生改造

岩体结构的表生改造是指河谷下切过程中 ,由于应力释放 ,岸坡岩体将向临空面方向发生卸荷回弹变形 ,谷坡应力场产生新的调整 ,伴随这一过程岩体结构所产生的一系列新的变异或变化。岩体结构的表生改造一般具有两类形式 ,即原有构造或原生结构面的进一步改造 ,或新的表生破裂体系的形成。其结果是在河谷岸坡一定深度范围内 ,形成类似于地下硐室围岩“松动圈”的岸坡卸荷带 ,从而恶化岩体的工程性状 ,降低结构面强度 ,对工程具有明显的影响和作用。该文采用有限元法模拟了某水电站坝区岩体结构的表生改造 ,探讨了地应力在表生改造中的作用 ,分析了表生改造对岩体结构的控制作用 ,为深入研究坝区岩体结构奠定了基础

EPIGENETIC REFORMATION OF THE ROCK MASS STRUCTURE IN A DEEP DOWNCUTTING GORGE

The epigenetic reformation of a rock mass is usually referred to a series of variation of the rock mass structure resulted from gorge stress field adjustment. In the process of a gorge downcutting, the rock mass near the slope will rebound toward the free surface due to stress relief. An unloading zone similar to the loosened zone around a tunnel is thus formed along the gorge slope in a certain depth. Therefore, the epigenetic reformation of the rock mass structure in a deep downcutting gorge can deteriorate the engineering behavior of the rock mass and decrease the strength of the structural discontinuity, which have a considerable influence on the rock mass engineering. The finite element method is used to model the epigenetic reformation of the rock mass structure of a large scale hydropower station. The effect of geostress on the epigenetic reformation is discussed in the paper. Such an approach is essential to the analysis of the rock mass structure at the dam site.