Stability analysis of earth slopes reinforced with micropiles

Micropiles are common reinforcements often used for slope stabilization under emergency conditions. In many circumstances they are extensively installed to cover a large area. A flow chart was suggested to calculate the factor of safety for micropile-reinforced slopes according to the shear strength reduction technique. Coupled analyses are performed for micropiles in a homogeneous slope with and without a thin weak layer. It is shown that the position of the micropiles has a significant impact on the failure mode of the reinforced slope for a homogeneous slope, indicating that the conventional design method based on uncoupled analysis in which the pile response and slope stability are considered separately is inaccurate. For relatively small embedment of micropiles, the response of micropiles is dominated by rigid-body rotation without substantial flexural distortion. The critical embedment depth to achieve fixed conditions at the base of the micropiles is found to range from 1.5 to 2 times the length above the sliding plane. Truncation of micropiles likely increases the capacity of the reinforcement system, and this benefit is particularly important for the slope with a thin weak layer. The largest truncation length of micropiles for homogeneous slopes and the slope with a thin weak layer is about 1/4 and 1/2 times the length above the sliding plane, respectively. The portion of truncated micropiles can be filled with soils and compacted in the standard procedure to decrease the cost in practice engineering.