Pile and Pier Foundations

In the design of pile and pier foundations the construction procedures play a significant and often dominant part in determining the extent of settlement that may occur. Settlements are examined under two simplified categories; (1) those that occur although adequate knowledge already exists for their prevention, and (2) those that occur for reasons inadequately understood. Because the first category is much the larger it is examined in most detail. Illustrations of excessive settlements caused by lack of knowledge of soil mechanics and of construction practices on the part of the designer are presented. The designer must be aware of the construction problems involved in his choice of foundation and transmit this awareness to the inspector. Examples of outdated knowledge and misconceptions still in use are given. Among the problems still requiring further investigation are (1) increase of point load with time of a pile passing through a compressible cohesive soil to embedment in a stiffer material, (2) estimation of settlements of long friction piles in cohesive soils of uniform or of stratified character, and (3) influence of the size of the pile group or foundation as a whole on the magnitude of settlement.