Pile foundations are extensively used to support. off-shore and on-shore structures. Under dynamic loads, the behavior of single pile is well understood. However the soil-pile-soil interaction studies are confusing, on which account the analyses do not necessarily predict response of the systems which may match satis-factorily with the performances. In this paper, the nature of dynamic loads is described, and solutions for soil-pile and pile-soil-pile inter-action solutions by several authors are presented and a critical evaluation is made.
Pile foundations are used extensively to support: heavy loads. The bulk of loads are static loads, which form the basis for fixing the section (size), embedded length and possibly configuration (spacing and arrangement) of the piles in the group. Dynamic loads are caused by nature e.g. earthquakes, winds, waves and by man-made vibrations eg machines, traffic and blasts. The design of piles for marine environment was discussed earlier (Prakash & Puri, 1992). The super-structure forms an integral part of the pile-foundation system. Therefore, an analysis of the structure-piIe-soils system and its proper understanding is desirable. Very little information is available on the behavior and analysis of the total system (Prakash et al 1992). The nature of loading and associated strain levels and soil-pile and pile group responses are quite different during dynamic loadin9 imposed by machines, earthquake, storm wave loading on off-shore structures. Machines may cause only small amplitude vibrations, and soils behave essentially as elastic materials. Earthquake loading on piles under buildings may cause large deformations resulting in non-linear soil behavior and considerable degradation of soil modulus. Interactions of the super-structure with piles is important. In off-shore structures, the piles are especially long and slender with considerable free-standing lengths. In this case even the pile material may behave in non-linear manner, and buckling of piles may also assume importance (Prakash 1985, 1987).
