| Methods for the prediction of pile performance are mainly developed from model pile tests and full-scale pile tests of less than 40m long in transported soils. Their predictability for high capacity long driven H-piles in weathered soils is in doubt. In this thesis, the final sets of 4,278 H-piles of 28-80m long, dynamic measurements of 255 of them and static loading tests of 13 instrumented piles from a site are studied. Pile behaviours caused by a hammer impact and under static test load are compared with 361 H-piles of 14-25m long from another site and theoretical predictions. Measured data revealed that the load-transfer mechanism varied with pile length and applied load. Piles deformed almost linearly with increased load and might fail in buckling with or without large plastic deformation. Unit side resistance degraded after prolonged hard driving. Maximum impact forces at final set were scatter but their means were insensitive to hammer type, ram weight, ram drop and pile length. Maximum impact compression of pile and affected pile length existed. Creep settlement and set-up effect in weathered soils were quantified. Geotechnical design parameters for local soils were calibrated. Factors affecting dynamic soil parameters were explained. Two improvements to the predictions were proposed. The energy-based equation uses the final sets and energy transferred to pile head to estimate the affected pile length. Piles longer than the length estimated will be considered as long piles and existing theories have to be applied with caution. If this length is used instead of full pile length in Hiley formula, predictability of the formula can be improved. The advantages of this modification to Hiley formula are its simplicity to use in field and the low cost compared with the stress-wave monitoring techniques. The new Case damping model approximates the Case damping factor as the sum of hysteretic damping of pile and viscous damping of surrounding soil. Based on this model, the effects of variation in load-distribution along pile shaft and set-up of pile in layered soils, and the incomplete mobilization of soil at pile toes to the Case damping factor can be explained. |
