Stability Assessment of Bolt-Supported Road Cutting Dip Slopes Using Discrete-Element and Limit-Analysis Methods

Abstract

Fully grouted bolts are widely used to reinforce road cutting slopes because of their low cost and high efficiency. However, there is a lack of research on the anchorage failure mechanism and stability assessment of bolt-supported road cutting dip slopes (BRCDSs). In this work, a progressive failure process of BRCDSs was captured via a triangular block model in the Universal Distinct Element Code (UDEC). A kinematically admissible velocity field of BRCDSs was innovatively established based on their sliding shear failure and the Mohr–Coulomb criterion. As a consequence, a novel method for evaluating the stability of BRCDSs was proposed using the upper bound theorem of limit analysis. The reinforcement effects of BRCDSs with different bolt angles were subsequently evaluated by UDEC simulations, and the obtained slope safety factors and bolt-supporting forces were compared with the results calculated by the proposed method. In addition, the influence of various parameters (bolt angle, bolt diameter, slope angle, and strengths of rock and discontinuity) on the reinforcement effect was investigated. The results obtained using the proposed method showed good agreement with those obtained via UDEC. There is an optimal bolt angle in BRCDSs, at which the bolt generates the largest supporting force and thus promotes the highest safety factor of the slope, and the value of this angle is approximated as the friction angle of the discontinuity. The safety factor of the slope also increases with the increase of bolt diameter, and the variation increasing according to a power function. The method proposed provided a convenient theoretical tool for the stability assessment and reinforcement design of BRCDSs.