Direct CPT Method for 130 Footings on Sands

Using the concept of a characteristic load-displacement curve for shallow foundations, a direct design method based on cone penetration testing (CPT) is applied to a database compiled from a total 130 footings on sands. Performance results are based solely on field load test data from large foundations (B >0.5 m) in order to avoid known scaling effects from small model size footings. The footing responses are presented in terms of applied stress (p_F) versus square root of normalized displacements (s/B) so that a single parameter represents the behavior of all size foundations on the particular sand. Furthermore, footing stresses are normalized by the cone tip resistance (q_c) to obtain a unique relationship for shallow foundations on sands. While the method was originally developed from field load tests on square and circular footings, it is now extended to include rectangular foundations via elasticity solutions using a dimensionless length-to-width ratio. Limited data from eight footings on calcareous sands also show compatibility with the derived algorithm.