Parametric studies on the lateral restraints of pile caps in soil

The general behaviours of pile caps with vertical rectangular faces embedded in soil mass idealised as a semi-infinite elastic continuum under lateral shears and on-plan torsions are discussed in this paper. Approaches based on the elastic continuum theory with consideration of the soil pressure limited to the passive pressure values have been formulated for the estimation of lateral displacements and on-plan rotations of the pile cap. Based on the findings, parametric studies are then conducted with the production of tables for users to estimate the lateral translational and torsional resistances of pile caps and subsequently, their displacements and rotations under lateral shears and/or on-plan torsions. These tables, though not exactly reflecting the true elasto-plastic behaviour, give conservative results which are also fairly accurate as compared with that yielded by the elasto-plastic theory. The tables can therefore serve as a quick check for users without going into more sophisticated analyses such as the tedious finite element analysis by computer software. As a demonstration of the use of the tables, the method for determination of the combined actions of the pile cap and the pile group under lateral loads is also included, with the illustration of a worked example. Finally, the applicability and limitations of the approach in real cases including underground obstructions and non-homogeneity of soil properties are discussed.