The objective of this research work was to gain a better understanding of the interaction between loads applied on the surface of soils, and the behaviour of adjacent long, vertical piles, embedded at depth in a stiff substratum. The influence of lateral thrust on the piles in an upper soft clay layer, due to simulated embankment construction, was examined and soil-pile interaction mechanisms were identified both for behaviour at working load and at the ultimate lateral capacity.
The performance of a row of free headed piles and of a pile group were investigated experimentally in the geotechnical centrifuge for different pile and foundation geometries. Pile response, in terms of bending moment, deflection and lateral pressure, was determined for surcharge loads applied to the centrifuge model.
This experimental database was used to calibrate a three dimensional finite element analysis of the same, simplified, model. These investigations led to the development of an approximate formula for lateral loading, based on the differential movement between the piles and the surrounding soil, which accounted for pile spacing. relative pile-soil stiffness and the degree of soil strength mobilisation. This loading function was incorporated in a computer program, SIMPLE, which calculated the pile bending moment and deflection profiles for flexible piles and pile groups. The algorithm was checked against the centrifuge model test results and the numerical analyses, and design charts were produced for free headed piles only_ Finally a design procedure was recommended for piled full-height bridge abutments and other facilities which feature passive lateral loading of piles by a nearby surcharge.