Abstract: Based on successful reinforcement projects of the sliding zone of the ancient debris landslide with applying deep high pressure grouting method, and combined with various detection measures and elastoplastic finite element analysis, the mechanism of deep high pressure grouting to reinforce sliding zone, physico-mechanical parameters of the soil in sliding zone before and after grouting, the remnant sliding force and safety factors of the landslide have been studied. Electron microscopy experiments show that, The filling replacement rate of cement slurry to rock and soil in sliding zone is 5%～10%. The soil tests results indicate that the soil cohesion increase from 20.20 kPa to 39.54 kPa and its internal friction angle from 16° to 21.30°. The sound wave CT scanning experiments show that the sound wave velocity of the soil in the sliding zone increases about 31%. The finite element analysis show that pressure grouting could make the unstable landslide go into the basic stable state and the remnant sliding force reduces a lot. These can provide optimization basis for retaining structure design. Tests and calculation results show that high pressure grouting method for enhancing the rock and soil in sliding zone is feasibility. The mechanical performance of the rock and soil in sliding zone has been significantly improved and the safety of the slope has been enhanced.

Key words: slope reinforcement, high pressure grouting, strength parameter, sliding zone