Soil Structure Interaction Analysis of a Berthing Structure Under Lateral Loading-By Numerical Approach

In coastal and offshore structures, the predominant forces leading to lateral movements are mainly due to waves, currents, winds, berthing forces, mooring forces and lateral earth pressure due to unstable slope as a result of dredging or siltation etc. Due to relative movement between the piles and the soil, the load transfer to pile is a complex soil interaction problem. It is a two way problem and should be solved by structure-soil model with appropriate load displacement characteristics of both the structure and the soil. Pile-soil interaction analysis is carried out by numerical methods based on iterative techniques of equilibrium of forces and moments, based on relative stiffness of pile-soil system. Conventionally API guidelines and Vesic equation are used to analyze the laterally loaded piles. The study of laterally loaded pile in active soil wedge requires a proper assessment of soil structure interaction phenomenon involving the interaction between pile surface and the surrounding soil. The instability of soil wedge can occur due to self-weight, surcharge load, dredging, siltation and earthquake force. The soil structure interaction problem of piles located in active soil wedge has rarely been approached. Laterally loaded piles are analyzed by methods derived from the classical beam on elastic foundation mode in which the soil support is approximated by a series of independent elastic spring. The soil spring constants estimated from API guidelines and Vesic equations are not suitable for piles located in active soil wedge. Hence in this paper, a numerical study is carried out for a berthing structure in dense sand using PLAXIS 3D and STAAD Pro, in order to study the behaviour of piles in active soil wedge.