NUMERICAL MODELING OF PILED RAFT FOUNDATION

Abstract

For a given geotechnical condition, when the raft foundation is not able to meet load requirement, in that case it is possible to enhance the performance of the raft by the adding piles beneath the raft. Strategically located number of piles may improve both the ultimate load capacity and the settlement of the raft. In recent years, combined piled raft foundation has been proved effective and appropriate method instead of conventional pile or raft foundation. In present work, Bearing capacity and settlement of raft and pile group have been calculated from analytically and same is simulated by finite element based software PLAXIS 2D. Based on this simulation between analytically and numerical methods, piled raft foundation is analyzed in PLAXIS 2D. And Settlement behavior of piled raft is studied by varying different parameters of soil, raft and pile. Foundations analysis and designing of raft and pile group have been carried out using STAAD.PRO and STAAD.FOUNDATION to calculate required steel and concrete area. After carrying out analysis of piled-raft foundation in sandy soil, using PLAXIS 2D,it was observed that settlement reduces as the pile length and number of pile group increases. The settlement of the pile group decreases as spacing ratio(s/d) increases up to certain spacing. Raft thickness doesn’t greatly influence the settlement. Settlement decreases as number of piles, pile length and modulus of elasticity of soil increases. Cost comparisons have been done between raft and piled raft foundation which foundation is more effective and economical. After cost comparison it is found that raft foundation can provide sufficient load capacity, and can go upto certain storey. But for high rise building in same soil condition then piled raft could be effective and economical option then pile foundation.