Laboratory Study on Diffusion and Migration of Grout in Rock Mass Fracture Network

Abstract

The flow process of grout in a rock mass fracture network is an important part to judge the effect of grouting in engineering. Till date, little research has been done on the diffusion and migration pattern of grout in a random fracture network. Based on this, herein, a visualized fracture grouting test system with constant pressure was developed, consisting of pressure supply equipment, constant-pressure pulping equipment, fracture simulation equipment, and monitoring equipment. The system can simulate the flow process of the fracture network under the effect of various parameters such as the grouting pressure, grout characteristics, and fracture aperture and achieve the real-time monitoring of grout pressure, flow velocity, and diffusion distance in a random fracture network. Also, the governing equation of grout flow in a single rough fracture was obtained. The reliability of the test system was proved by the comparison of the single fracture grouting theory with the test results. Moreover, the grouting diffusion mechanism of the random fracture network was studied. The results show that (1) the pressure at the same point in the fracture increased with an increase in the grouting pressure and a decrease in the fracture aperture and was not affected by a change in the grout viscosity. (2) After the grout was dispersed into several branches in the fracture network, the pressures dropped significantly, the flow velocity decreased, and the pressure of each branch and flow distribution coefficient were greatly affected by the angle of bifurcation (intersection) fracture. The development of a test system and study results has a certain guiding value for grouting engineering.