Alternative foundation system for piles with soft toe condition

Abstract

This paper presents an alternative foundation system implemented for a 17 storied mixed development building at Kollupitiya. Initially, the foundation system of above building was designed to contain bored cast insitu piles driven to hard basement rock. During pile dynamic testing, the tested piles were found to undergo excessive settlements and failed to mobilize the expected design capacity due to soft toe condition. As an alternative for this problem, piled raft system was proposed and its feasibility was examined. Finite element modelling and analysis was carried out using SAFE v12 representing the raft as shell element and piles as springs. The simulation design and process is discussed in detail in this paper. The ‘conventional approach’ was highlighted in the design of raft with a load apportionment of 60:40 to piles and raft. While replacement of failed piles and rectification of piles incur significant time, cost and resources, the proposed piled raft system was found to be a sustainable and economical solution with least disturbance to the ground.