Damage evolution of hydraulically coupled Jianchuandong dangerous rock mass

Abstract

Submerged rock masses in reservoir areas can be dangerous when the base rock mass is located in a deterioration zone formed by periodic water level fluctuations. Deformation of the base rock mass is driven by compression due to its own overlying weight and the hydrological conditions of the reservoir; the combination of these two factors represents a complex mechanical environment. This hydraulic coupling accelerates the deterioration and the instability of the base rock mass. To investigate the Jianchuandong dangerous rock mass (JDRM) in the Three Gorges Reservoir area, we devised a new hydraulic coupling mechanism that, when applied to a generalized mechanics model, represents the mechanical environment of the base rock mass in the deterioration zone. In this hydraulic coupling mechanism, when water is in direct contact with the rock mass, the water pressure contributes to the expansion of existing fractures in the JDRM base rock mass. With this hydraulic coupling mechanism, we created a constitutive damage model that reflects the observed stress-strain characteristics of the JDRM base rock mass in these hydrological conditions. After refining our model by incorporating the damage experienced by the submerged dangerous rock mass over time, we determined that the eventual failure of the JDRM can be divided into three stages: the formation of the bottom damage zone, progressive deformation and damage, and sudden rock collapse. Our model indicates that the damage can magnify the effective stress experienced by the base rock mass and lead to the nonlinear acceleration of the deterioration of the dangerous rock mass.