Numerical analyses of load tests on bored piles

Abstract

A back analysis of a load test of a bored pile is shown. This short large diameter bored pile was tested in Germany and results for the total resistance as well as results for the base and the shaft resistance are available. In the FE-analysis the pile is assumed to be linear elastic and for the subsoil three different constitutive models are used, i.e. the elastic-plastic Mohr-Coulomb model, the Soft-Soil model, which is based on the modified Cam-Clay model, and the advanced Hardening-Soil model. These models are introduced briefly. In a first step the influence of the mesh and of interface elements is discussed. Finally the results of the three models are compared with the results of the pile load test. The acceptance of numerical analyses in geotechnical problems is growing and finite element calculations are more and more used in the design of foundations. In particular for the design of piled raft foundations. Nevertheless the bearing capacity of a single pile is most usually determined by pile load tests or by empir- ical methods. For this reason numerical analyses of a load test on a bored pile in stiff clay are shown in full detail and modelling aspects will be discussed. In the paper the influence of several variables on the load- settlement behaviour of the pile are discussed, i.e. the mesh dependency as well as the effect of interface elements. Different constitutive models are used to simulate the mechanical behaviour of the soil. Finally the results of the numerical analyses are compared with the results of the pile load test. 2 CONSTITUTIVE MODELS