Use of Compressible Layer for Raft Footing Design with Winkler Method

Raft footing is a commonly used shallow foundation system, which is largely contingent upon the founding condition. The primary challenges encountered in footing design often revolve around managing maximum settlement and differential settlement. The Winkler method is commonly employed to analyze a raft footing by modelling the founding soil as discrete elements characterized with soil subgrade modulus (ks). The stiffness of the subgrade modulus is largely influenced by the Young's modulus of founding material (Es), the Poisson's ratio of soil (υ), and the width of the footing (B). An innovative approach of employing compressible layers beneath a raft footing to reduce its effective footing width for design. These compressible layers, strategically positioned under low-loaded concentrated areas or the middle portion of the raft, enable control over the effective width of the footing, leading to an increased soil subgrade modulus (ks). The outcomes include significant improvement on calculated values for maximum settlement and differential settlement.