USE OF MICROPILE IN SLOPE STABILIZATION

Abstract

Slope failures damage the constructed structures over slopes and sometimes cause loss of human life, so slopes must be stabilized before failures occur. In this study, slopes has been stabilized using micro piles. Several techniques are used to analyze slope stability. In this study, the slope stability analysis is done by PLAXIS 3D, a finite element software. The factor of safety (FOS) unreinforced slopes has been calculated, and micro piles are installed to improve it. Then again, FOS has been calculated for optimum location, inclination, and embedment length of micropile which has been found using PLAXIS 3D software. From the results of the study carried out using PLAXIS 3D software, it has been found that the location of micropile for the maximum factor of safety depends upon the type of soil. The parametric study has been carried out for two soil models first one has cohesion value as 20 kN/m2 and friction angle as 20⁰ and second one is sandy soil which has cohesion value as 2 kN/m2 and friction angle as 33⁰. It has been observed that the optimum location of micropile for soil from first model is at small distance away from the middle in the crest side direction. For second model, that is sandy soil, it is exactly in the middle of the slope. In this study has been found that Micropiles installed at toe of the slope and at near the crest of the slope does not improve the stability of slope in a significant manner for both the models. Micropile has been installed at a different inclination from vertical axis at the optimum location for both the soil models. It was found that the optimum angle of inclination for soil model one is 50⁰ from the vertical axis. For model two soils, that is Sandy soil, the inclination of micropile has a negligible effect on the factor of safety value. Micropile diameter has not any significant impact on the factor of safety in model one soil. For model two soil, that is sandy soils, if the diameter increases, the safety factor increases up to a critical value. After this no improvement in the factor of safety has been observed with an increase in diameter. When the spacing of the micropile increases, the value of factor of safety decreases but the decrease in the factor of safety value is more when spacing of micropile increases more than three times the diameter of the micropile, so spacing of three times diameter of micropile has been selected as optimum spacing for micropile. Length of micropile influences the stability of slopes reinforced with micropile. The parametric study concludes that if the length of micropile below the failure surface increases up to two times the micropile length above the failure surface, the factor of safety increases, but after this critical value, the improvement is not significant.