Numerical Investigation of Grouting of Rock Mass with Fracture Propagation Using Cohesive Finite Elements

Abstract

The grouting of a rock mass is frequently adopted in engineering to enhance the strength and integrity of jointed rock. Based on the principle of hydraulic fracturing, grouting slurry with high pressure is injected into the rock mass, resulting in the emergence and propagation of hydraulic fracture. In this work, a numerical model with cohesive finite elements was developed to simulate the grouting of a rock mass, which couples the stress-seepage-damage field. The model considers the fluid exchange between the porous, permeable medium and fractures, in addition to the coupling of fluid exchange and rock deformation. The effect of fluid lag on pore pressure in the vicinity of the fracture tip is specifically analyzed. Results show that the variation of pore pressure in the broken cohesive zone can be divided into four stages: the initial steady-wave stage, descending stage, sharp-rise stage, and fluctuation-rise stage. There is a significant region of lowered pore pressure in the vicinity of the fracture tip as a result of the effect of fluid lag.