Abstract: Based on the curtain grouting engineering of Zhongjiashan tunnel, a large-scale model test device is designed to simulate the process of fracture grouting in fault fracture zone. The variation law of key parameters during the grouting are recorded and analyzed by layouting monitoring components, and the distribution of grouting veins are exposed intuitively by excavating the filling medium. The test results show that the fracturing pressure presents a pulse-like law during the grouting process, and the first fracturing pressure under the conditions of this test is 0.12 MPa which is made a comparative analysis with the existing theoretical solution. The change mechanism of fracturing pressure is analyzed based on the conversion of slurry diffusion form, saturation of primary and secondary fracturing channels, formation of new fracturing channels and saturation of the follow-up fracturing zone. The definition methods of primary and secondary fracturing pressure are proposed; then 7 primary fracturing pressure and 53 secondary fracturing pressure under the conditions of this test are found to show an increasing law approximately. Based on the p-t curve, the fracturing process of soil are divided into 3 stages including the energy accumulation, soil fracturing and slurry energy transfer from the perspective of energy dissipation. The spatial distribution law and coexistence law of primary and secondary grouting veins are found by excavating the filling medium. The site application test is carried out in curtain grouting engineering of Zhongjiashan tunnel to verify the correctness of test results. The test results play a guiding role on the understanding of grouting theory and the application of grouting engineering to some extent.

Key words: fault fracture zone, model test, fracture grouting, fracturing pressure, primary fracture, secondary fracture, distribution of grouting veins