SETTLEMENT ANALYSIS OF PILED RAFT FOUNDATIONS

Abstract

Piled raft foundations are adopted to reduce the total and differential settlements of foundations. In this work, an analysis to obtain the settlement profile of piled rafts is presented using plate on springs approach. The analysis is carried out using ANSYS 7.0. In this approach the raft is represented by an elastic plate, the soil is replaced by equivalent Sfrr 61 `kten 4+44"k springs at nodal points, and the piles are modelled asstiff springs. Load-settlement response ef of pile has been estimated to compute the stiffness of the spring at pile locations using load transfer approach suggested by Hazarika and Ramasamy (2000). Similarly, load-settlement response of the raft has been estimated to compute the stiffness of the soil spring (softer spring) using De-Beer and Marten's (1957) method in the case of cohesionless soils and consolidation test data in the case of cohesive soils. The method takes into account a layered soil system. A user-friendly computer package has been developed in Visual Basic 6.0 programming language to develop the load-settlement response curves for raft as well as for piles. Using ANSYS 7.0 computer package, a number of typical case studies have been analysed and the results are presented. The settlement profile obtained using the analysis agrees well with the reported measured settlement values.