Dynamic Determination of Pile Capacity

Abstract

A method is presented for determining the axial static pile capacity from dynamic measurements of force and acceleration made under the impact of a large hammer. The basic equation for calculation of the forces resisting pile penetration is derived. The limitations of the basic resistance equation are discussed and illustrative examples of field measurements are given. With the availability of this derivation, it is possible to prove that the Case Pile Wave Analysis Program (CAPWAP) resistance force distribution is unique. Using the assumption that the resistance to penetration can be divided into static and dynamic parts, an expression is developed for calculating the dynamic, resistance to penetration. The resulting method requires the selection of a damping constant which is shown empirically, to relate to soil size distribution. A correlation of Case Method capacity and the capacity observed in static logd tests is given for 69 statically tested piles that were also tested dynamically.