Optimization of Piled Raft Foundation to Study the Load Sharing and Settlement Behavior in Sand

Abstract

Piled raft foundation in the combination of both shallow and deep foundation systems. The capacity of raft is included in pile foundation design to make it economical. The individual aspect of the influence parameters such as pile numbers, spacing, length and diameter is studied for load-settlement analysis under uniform vertical load in loose sand. The load sharing mechanism is examined considering the settlement governing variations simultaneously. PLAXIS 3D software used for numerical analysis. The pile length and diameter is so adjusted that the l/d ratio are 12, 16 and 20. In numerical modeling, Mohr- coulomb model is used for dry sand and elastic linear model is used for pile and raft. The soil properties are determined through direct shear test, relative density, sieve analysis and specific gravity test and empirical equations. Small scale physical model test performed in laboratory for validation of numerical modeling results. A field case study is solved with PLAXIS 3D software and simplified hand calculation method of Poulos-Davis-Randolph (PDR). The results shows that pile diameter, length, number, and spacing of piles have positive impact in bearing capacity enhancement of piled raft foundation. Load sharing mechanism also influenced by these variables as pile share increase with the increase in above mentioned variables.