Bearing capacity of long driven piles using dynamic methods

Although dynamic methods such as driving formulas and wave equation analyses have been used for the determination of the bearing capacity of piles for decades, experience with dynamic methods for very long piles is still limited. This papers aims at evaluating performance of Hiley's formula and a wave equation program GRLWEAP using four cases of very long steel H-piles driven into weathered materials. The pile length studied varies from 78 in to 108 in. The geotechnical pile capacities and pile driving characteristics predicted using Hiley's formula and GRLWEAP are compared and the maximum stresses during installation of these long piles are studied. The wave equation analysis shows superiority over Hiley's formula at hard driving. For the four cases studied, the pile capacity values from Hiley's formula are consistently lower than those from the wave equation analysis and from a static load test.