To assess the stability of large-scale underground caverns within steeply dipping rock strata, a high-resolution microseismic monitoring system was deployed in the right-bank underground powerhouse of the Wudongde hydropower station in southwest China. The progression of damage in the surrounding rock mass, including the initiation, propagation, coalescence, and interaction of rock microfractures, was first demonstrated by analysing the temporal and spatial distribution of microseismic activity. The microseismic monitoring results were validated using conventional monitoring data and field observations. A typical failure of the surrounding rock mass was observed, and data on the evolution of the microseismicity and its corresponding mechanism during the development of this failure was also obtained. The results provide an overall understanding of the progressive damage and failure evolution in large-scale underground openings.
Layered rock masses are widely distributed on land. During formation of this kind of rock mass, differences in material composition, particle size, colour, and fabric result in rock stratification. Consequently, a set of dominant and parallel discontinuities, called bedding planes, is generated. As can be expected, these bedding planes play a vital role in the stability of engineering projects in layered rocks, and in particular in their modes of failure. Hence, the mechanics of the failure mechanism in stratified rock masses has its own distinctive features. Many large-scale underground openings have been constructed recently in stratified rock masses, due to their universal distribution. Therefore, it is of significance to study the failure modes and mechanism of underground openings in layered rock masses.
