Accelerations of a driven pile and the surrounding soil

摘要

The traditional mathematical formulation of pile driving (e.g Smith, 1960) assumes that the soil surrounding the penetrating object remains stationary while one-dimensional wave propagation takes place in the pile. Paikowsky and Chernauskas (1996) examined large data sets of driven piles and suggested that the soil's inertia greatly affects the actual physical phenomenon controlling pile resistance during driving and hence the accuracy of the dynamic methods. Due to the fact that soil inertia is not accounted for by most traditional pile driving models, a new, practical model needs to be developed that accounts for this factor in a routine manner. The development of a reliable pile-driving model incorporating soil inertia requires an understanding of the relationship between pile penetration and soil motion. Hoelscher (1995) investigated these relationships in a laboratory and field study. To enhance the understanding of the problem, the presented research examines the measurements of pile and soil accelerations during the installation of a closed ended steel pipe pile at a bridge reconstruction site in Newbury, Massachusetts. The steel pipe pile, part of a test pile cluster investigating time dependent pile capacity in the Boston Area, was instrumented with accelerometers and strain gages at the pile top, middle, and tip. Ground accelerometers, piezometers, and total pressure cells were installed in a silty sand layer about 19.5m from the ground surface at various distances from the pile. The layout and installation of the pile and soil instrumentation is provided. Measurements showing the effect of pile installation as the pile tip passes by the soil instrumentation are shown. Analysis of the pile and soil instrumentation measurements showed (ⅰ) such measurements are possible and provide insight into the behavior of the soil during pile penetration and (ii) the majority of soil disturbance occurred at or near the pile tip.