Stability Analysis of Pile-Supported Embankments over Soft Clay Considering Soil Failure between Piles Based on Upper Bound Theorem

Most analytical methods used to analyze the stability of pile-supported embankments are based on shear and bending failure of piles. However, the centrifuge test and practical engineering show that rigid pile-supported embankments have a failure mode of soil sliding around piles. Therefore, the stability analysis method of the pile-supported embankment under the failure mode of the soil sliding around piles based on the upper bound theorem is given in this study. First, the failure mechanism is assumed to be a rigid body and slide along two logarithmic spiral surfaces in the embankment and soft soil. The rate of external work and internal energy dissipation of the failure mechanism are further obtained, wherein the internal energy dissipation rate of piles is obtained based on the limit state of soil sliding around piles. Secondly, according to the equation formed by the upper bound theorem, the optimization model of the safety factor function when the potential slip surface is passing through different pile rows is obtained. Then, the algorithm of solving the model is given and the overall safety factor of the pile-supported embankment is obtained. Compared with other methods, the advantage of this method is that it considers the influence of embankment soil property and the width perpendicular to the two-dimensional plane on the pile load and the influence of the soil internal friction angle on the slip surface. Finally, it can be concluded from parametric analysis that: with the increase of the horizontal distance from piles to the slope toe, the reinforcement effect of piles first increases and then decreases; with the decrease of the embankment height and the increase of the soft soil cohesion and internal friction angle, the overall safety factor of the embankment increases.