PREDICTING PILE STATIC BEARING CAPACITY FROM DYNAMIC TESTS

THE PAPER UNDERTAKES PREDICTION OF FRICTION PILE STATIC BEARING CAPACITY FROM DYNAMIC MEASUREMENTS OF FORCE AND ACCELERATION TAKEN AT THE TOP OF THE PILE DURING THE DRIVING PROCESS. THE ANALYSIS SCHEME INVOLVES THE USE OF THE ONE-DIMENSIONAL STRAIN-WAVE EQUATION TOGETHER WITH AN ARBITRARILY ASSUMED SOIL RESISTANCE UNIFORMLY DISTRIBUTED ALONG THE LENGTH OF THE PILE. THIS RESISTIVE FORCE IS ASSUMED TO BEGIN ACTING JUST AFTER THE INITIAL ELASTIC WAVE HAS TRAVELLED THE LENGTH OF THE PILE. ALL CALCULATIONS OF BEARING CAPACITY ARE COMPARED WITH RESULTS OF PILE STATIC TESTS MADE IN THE FIELD NEAR THE TIME OF THE DYNAMIC TESTS. THESE COMPARISONS INDICATE AN ENCOURAGING SUCCESS OF THE METHOD FOR THE EXAMPLES AND SOIL CONSIDERED. THE ESSENCE OF THE PREDICTION SCHEME FOR STATIC BEARING CAPACITY IS THE DEMONSTRATION THAT, AFTER HAMMER IMPACT, A LONG PILE FIRST UNDERGOES AN INITIAL PERIOD OF COMPRESSION AND THEREAFTER ACTS MORE OR LESS LIKE A RIGID BODY WITH ELASTIC PERTURBATIONS. THE AVERAGE SOIL RESISTANCE, PARTICULARLY IN THE NEIGHBORHOOD OF ZERO PILE VELOCITY, IS SHOWN TO BE A GOOD ESTIMATE OF PILE STATIC BEARING CAPACITY, VALID JUST AFTER DRIVING. /AUTHOR/