Design method of micropile group for soil slope stabilization based on ultimate resistance of analysis

As a kind of measure for fast slope reinforcement, micropiles are always designed as a group. An analytic model for the ultimate resistance of the micropiles is proposed based on the beam-column equation and the existing P-y curve method, and then an iterative process to find the bending moment and shear capacity of the micropile section is developed. The formulation for calculating the inner force and deflection of the micropiles using the finite difference method is derived. Special attention is paid to determine the spacing of the micropiles, aiming to get the ultimate shear capacity of micropile group. Thus a new design method of micropile group for soil slope stabilization is proposed, including choosing a location for the micropile group within the existing slope, selecting micropile cross section, estimating length of micropile, evaluating shear capacity of micropile group and calculating spacing required to provide force to stabilize the slope and design of concrete cap beams. The application of the method to an embankment slope hazard problem in Qinghai is described, and the monitoring data indicate that slope movement is effectively controlled as a result of the slope stabilization measure, which verifies the reasonability of the design method.