Pile tip bearing capacity in rock masses: analytical and numerical analysis comparison

Abstract

This paper researches the different approaches to calculate the ultimate bearing capacity at the pile tip embedded in a homogenous rock mass characterized by the modified Hoek and Brown failure criterion. The main objective is to analyze the performance of the novel Discontinuity Layout Optimization method (DLO), which directly calculates the limit load, instead of using a load convergence scheme, being first applied here to the complex problem of piles in rock. The DLO results are validated against the available analytical solution and the Finite Difference Method (FDM) results, for wide range of geometric and geotechnical parameters. Perfect plasticity, plane strain conditions, associated flow rule, the modified Hoek and Brown failure criterion, and weightless rock media are considered in all models. The comparison between solutions is expressed by a percentage difference considering the analytical solution or the numerical solution as a reference. Results relative to DLO and FDM differences against the analytical solutions point towards some limitations of the analytical solution and that the numerical model does not reproduce exactly the analytical solution hypotheses. From the analysis, DLO demonstrates to be a very efficient and accurate tool to address the tip-of-pile bearing capacity, presenting considerable advantages over other methods.