Back analysis of lateral load test on piles

Abstract

A simple nonlinear soil model is presented based on an initial small strain stiffness, a yield pressure and an index 'n' that controls nonlinearity. This model first proposed by Pender and implemented by Carter was developed to simplify the specification of p-y curves. Using this model a finite element program was written by Carter based on the concept of Winkler springs. It has been the aim of this thesis to use the computer program to back analyse the observed behaviour of full scale field test on lateral load behaviour of piled foundation to determine how well the soil model presented can predict behaviour measured in field. Results of back analysis of twenty eight piles have shown that the soil model, although not as intricate as the p-y curves, is able to predict the deformation characteristic with a similar degree of accuracy. The effect of changes in pile width on the initial small strain stiffness is investigated. The best agreement between measured and computed pile response is obtained using a linear relationship between the modulus and the pile width. Various authors have proposed a limiting reaction pressure that can be mobilised by the soil. For cohesionless soils a limiting pressure distribution which increases at a rate of 5KpL gave the closest match. For cohesive soils ultimate pressures which increases iinearly from 5s, at the surface to 12s, at depth is most appropriate. The versatility of the above soil model has been clearly demonstrated in this thesis.