A New Technique for Reduction of Excess Pore Pressures During Pile Driving

Abstract

A new technique is described whereby excess pore pressures induced during pile driving in soft, varved silts and clays were economically reduced to a safe level. The technique was applied to piles at a bridge site south of Stockholm, Sweden, where a small slide had occurred during pile driving. A new paper–plastic drain was attached to the wood piles during driving, and two pulling tests indicated that the drain was undamaged under normal driving conditions. The excess pore pressure generated during the driving of some 13 test piles without drains and 48 piles with drains was measured. The data indicated at least a 50% relative reduction in excess pore pressure when the drain was used. In addition, the cost of the technique was considerably less than alternative methods for dealing with dangerous excess pore water pressures resulting from piling in similar soils. The technique has been successfully applied at two other piling sites in Sweden.