Automatic signal matching with CAPWAP

摘要

CAPWAP(~R) Provides the most reliable means of analyzing dynamic pile top force and velocity records from the Pile Analyzer(~R) (PDA). This is a signal matching approach which requires that certain soil parameters are adjusted until measured and calculated pile top variables reach a reasonable match. The number of unknown soil parameters depends on the depth of pile penetration and therefore the computational effort can be appreciable if the pile is long. The process can be either done in an interactive manner or automatically with great time savings. Current practice requires that the automatic results are checked by interactive analysis. In an attempt to make the automatic solution reliable, several additional matching parameters have been included in the CAPWAP model. Among these variables, the most important is the final set (inverse of blow count) of the hammer blow analyzed. Unfortunately, since restrike data is usually analyzed by CAPWAP for long term static capacity predictions, final set is not always accurately known. For this reason a study was undertaken to evaluate the accuracy of the automated CAPWAP results including blow count matching compared to the traditional approach. More than 30 cases where static load tests and restrike tests had been performed were analyzed using the automatic procedure provided by the Windows based CAPWAP Version 1999-1. This program also calculates the total dynamic resistance (the sum of damping and static resistance) allowing for an assessment of the ratio of total dynamic resistance to static resistance and its relationship with soil type.