Calculation Method for Unstable Rock Stability based on Dominant Fissure Model

Abstract

In accordance with in-situ exploration and years of experience in unstable rock-related design, this paper states that the Mohr-Coulomb model is insufficient for the selection of the shear strength parameters of the dominant fissure of unstable rocks. Therefore, a JRC-JCS model of dominant fissure for three types of unstable rocks was established, which is more applicable to construction practice. Based on this model, calculation methods were obtained for the three types of unstable rocks, and the stability coefficient expressions of the unstable rocks were determined. The stability of five typical unstable rocks in Wanzhou District, Chongqing Municipality, China, namely, W12, W22, W59, W4, and W16, was calculated by these methods. As indicated by the calculation results, the unstable sliding rock W12, unstable toppling rock W22, and unstable falling rock W4 are stable, while the unstable toppling rock W59 and unstable falling rock W16 remain unstable and thus need reinforcing. These calculation results are relatively in line with the actual situation, according to a verification by in-situ monitoring from 2003 to 2013. This further verifies the practicality and applicability of the above calculation methods, which are based on the dominant fissure model. These methods also offer a theoretical basis for the amendment of the local standard, namely, Chongqing’s design specification for prevention and control projects of geological hazards (DB50/5029-2004), in terms of calculation methods for unstable rock stability.