| Current dynamic methods estimate pile bearing capacity through the measurements of in-pile stress wave. Typically, the accelerometer and the strain gauge are mounted to the pile shaft near the pile head. This on-pile instrumentation is expensive and it interrupts the driving operation. The high cost and interruptive nature of the on-pile instrumentation imposes practical limits on the number of piles to be tested. The limited amount of tested piles cannot reliably represent the rest of piles that might be driven through a variety of soil conditions.; This research aims at developing a new method for estimating pile bearing capacity through the off-pile measurements. The pile-soil system is modeled as a single-degree-freedom mass-spring-slider-dashpot system. Based on principle of vibration, the pile bearing capacity is analytically derived as a function of vibrating mass, damped natural frequency, damping ratio, and soil quake. The damped natural frequency and the damping ratio are measured from ground waves, and the vibrating mass and soil quake are estimated based upon in-situ soil properties. The measuring of ground waves needs no on-pile instrumentation, and would not interrupt the driving operation. This enables every pile at a site to be tested. The inaccuracy resulting from the variation of soil conditions can then be minimized.; The proposed method was examined using field data collected from a bridge foundation project. Given a reliable value of soil quake, the proposed method produce a value of bearing capacity close to the Case method bearing capacity. The results are reproducible and consistent with engineering principles and information reported in the literature. |
