Chapter 16 - Performance of Soft Clays Reinforced by Floating Columns

Abstract

This paper studies the reinforcement of very thick compressible soils by floating columns. Analysis is made on the basis of very recent methodology of design that combines the verifications of bearing capacity and settlement to provide the optimized improvement area ratio (IAR). Introducing the allowable long-term settlement of unreinforced compressible soil and assuming that the total short-term settlement is completed at the end of construction, an optimized length of floating columns is identified. The result highlights the feasibility of a potential solution of reinforcement in making a whole cost-effective design that includes the improvement area ratio within the reinforced soil layer and the thickness of unreinforced compressible layer in which column material is saved without any concern about the serviceability of built structures. Analysis of two case studies using floating stone column and soil treated column techniques enabled several solutions to be suggested by taking account of the columns’ length, optimized IAR, and, more importantly, an agreed-on allowable residual consolidation settlement within the unreinforced sublayer(s).