A study of dynamic load-deformation and damping properties of sands concerned with a pile-soil system

Despite various philosophies which have been proposed, our knowledge of the behavior of piled-foundation is still far from complete. This is partly due to the fact that the pile-soil interaction is markedly complex, particularly to the nature of pore-water pressure, the influence of void ratio, and the dynamic effect of soil. The wave equation method of pile driving analysis is believed to be a rational approach. This method considers many influencing factors such as the use of capblocks, pile caps, cushion blocks, composite piles, as well as shear characteristics of soils under dynamic loading. This exploratory study is concerned with dynamic load-deformation and damping properties of sand in the application of the wave equation method of pile-soil system. The effect of dynamic loading on the strength of both saturated and dry specimens was investigated by laboratory triaxial tests. A falling weight type test apparatus was constructed in order to achieve high rates of loading, such as 130 in. per sec., 90 in. per sec., and 40 in. per sec. Load was measured by a load cell which supported the specimen in a modified triaxial cell. The deformation was measured by a linear displacement transducer which detected the motion of loading piston of the triaxial cell. The pore-water pressure was also measured by a pressure transducer. The traces of load, deformation, and pore-water pressure were recorded with an oscilligraph visicorder. ..