Shear Properties of Grout-Rock Interface for Treatment of Mud Inrush

Grouting is an effective method to strengthen weak rock mass in tunnel engineering to prevent and control mud inrush disaster. The hardened grout-rock consolidation involves not only the properties of hardened grout, but also that of weak rock masses. As a transition region between them, the grout-rock interface determines the overall strength, then the shear properties of which was investigated in this study. The gushed mud from engineering project and a kind of Portland cement grout were selected as raw materials. A test system that can apply high injection pressure was developed to simulate the actual generation environment of grout-rock interface. By using it, two sets of samples with three different water-to-cement (W/C) ratios: 0.8, 1 and 1.5; and three different injection pressures: 1 MPa, 1.5 MPa and 2 MPa were prepared. After that, the direct shear test and SEM test were conducted to study the properties of grout-rock interface. The results show that lower W/C ratio and higher injection pressure can result in larger cohesive strength as well as internal friction angle of samples. When W/C ratio was decreased from 1.5 to 0.8, the former increased from 171.95 kPa to 251.55 kPa, and the latter rose from 32.31° to 41.71°. Also, they increased by 73.59 % and 17.64 %, respectively, with injection pressure ranging from 1 MPa to 2 MPa. It is hoped that the data provided will aid in the design of grouting with this material in the future.