Soil Resistance Predictions from Pile Dynamics

Abstract

An automated prediction scheme is presented which utilizes both force and acceleration records measured at the pile top during driving to compute the soil resistance forces acting along the pile. The distribution of these forces is determined, and the dynamic and static resistance forces are distinguished such that a prediction of a theoretical static load versus penetration curve is possible. As a theoretical basis stress wave theory is used, derived from the general solution of the linear one-dimensional wave equation. As a means of calculating the dynamic pile response, a lumped mass pile model is devised and solved by the Newmark β-method. Wave theory is also employed to develop a simple method for computing static bearing capacity from acceleration and force measurements. Twenty-four pile tests are reported, 14 of them with special instrumentation, i.e., strain gages along the pile below grade. The piles tested were of 12-in. (30-cm) diam. steel pile with lengths ranging from 33 ft. to 83 ft. (10 m to 25 m).