Growth and Mechanics of Brittle Fault Systems in Rock Mass: An Example of Baihetan Hydropower Dam Area

Abstract

Architectures of fault systems play important role in stability and mechanics of rock mass. While growth mechanism of faults is intrinsic controler for architectures of fault systems. This paper presents a case on faulting in the dam area of an oversized hydropower in Southwestern China. The faults in this area are mostly strike-slip faults with shallow brittle deformation characters, extending tens to hundreds of meters. These faults can be divided into four groups which are formed during two generations corresponds to two periods of tectonic events. Growth model of these faults have been built based on geologic and mechanic data. The first generation of faults was formed based on preexisting joints. While the secondary generation emerge only if the existing faults become critically misaligned during rotation of the primary stresses. The criterion laws for formation of secondary faults are suggested. According to the growth model, we can predict placement of secondary faults in space. Conversely, when geometry and space characters of the fault systems are known, we can estimate mechanic parameters and tectonic environments of the rock mass.