Abstract: This paper presents an investigation into the effect of secondary grout on the micropiles performance. A large number of in situ tests were performed on the slope stability mitigation reinforced with micropiles with secondary pressure grout. The characteristics of secondary pressure grout were evaluated. The results demonstrate that splitting pressure, continuous pressure and rocksoil cracking pressure can reflect the mechanisms and the effects of secondary pressure grout. These factors can be considered as the control indicators for the secondary pressure grout. The secondary pressure grout acting on the fully weathered shale formation can be divided into four categories: secondary pressure grout without splitting, secondary pressure grout with shortterm slurry injection, secondary pressure groutwithout crushing pressure and secondary pressure grout with crushing pressure.

Key words: Micropile with Secondary Pressure Grout, Slope Stabilization, InSitu Tests, Splitting Pressure