Effect of Raft Rigidity on Load Sharing of Piled Raft Foundations

Abstract

In the design of piled foundation, all loads are assumed to be transferred through the piles to the soil ignoring the load transferred by the raft to the soil. This study was performed in order study to the possibility of tokening the soil load sharing in the design. The objective of this study is to investigate raft rigidity effect on load sharing of piled raft foundations. Two groups (four piles each) of load testing were executed under axial compression for Piled-raft cap directly in contact with soil. The first group of load testing was carried out on a concrete pile cap while the second group was a steel cap. All groups consisted of installing four piles with different stiffness values. The loads transferred to the soil underneath the piled raft directly in contact with soil were measured by a load cell. The displacement, strains along the pile surfaces as well as transferred loads to the soil underneath piles cap were measured simultaneously. In addition, a finite element package of a PLAXIS 3D has been done to compare the theoretical and experimental results. The obtained test results indicated that the soil carried 3.5% to 5.80 % from the total load applied after redistributed of load from the soil. In addition, increasing rigidity of raft foundation decreases the load carried by soil and increases load carried by piles. However, increasing rigidity of raft foundation decreases the load carried by soil by a ratio from 27.3% to 36.85%, and increases the load carried by piles by a ratio from 28.3% to 53.67%.