Volume 26, Issue 1 (March 2003)
New Wave Equation Technique for High Strain Impact Testing of Driven Piles
The real time records of force and velocity measured at the pile head during each hammer impact constitute the so-called high strain test (HST) data in the modern wave equation technology in connection with pile-driving activities. Currently, the Case method and the CAPWAP match procedure represent the state-of-art in interpreting HST data to obtain useful information, such as bearing capacity of a pile, soil-pile interaction model parameters, and the hammer performance, etc. A new HST data interpretation procedure based on wave equation theories is developed in this paper. For the case where only toe resistance exists, the new method utilizes both force and velocity records to analytically compute the corresponding dynamic soil resistance at the toe of an impact-driven pile. An inverse optimization scheme is developed to use these analytically computed quantities to determine the pertinent soil-pile interaction model parameters. Examples are given to illustrate the use of the new method to determine the pertinent Smith model constants commonly used in modeling the dynamic soil-pile interactions. The developed algorithm is also successfully extended to the case in which both shaft and toe resistances are involved during pile driving.