A Review on the Behaviour of Combined Stone Columns and Pile Foundations in Soft Soils when Placed under Rigid Raft Foundation

In the last few decades, it has been observed that raft foundations are very commonly used as a foundation solution for moderate to high rise structures either by resting on stone columns or on piles in soft soils. It is believed that, combining stone columns and piles in one foundation system is the more suitable foundation for medium rise structures. The combined foundation system provides a superior and more economical alternative to pile, and a more attractive alternative to stone columns in respect to ground improvement. This paper presents the review of existing studies reported in the literature in the last two decades about the behaviour of stone columns under raft foundations and piled raft foundation in soft soil, notably the failure mechanism and the bearing capacity. Also, a limited work from the literature concerning the performance of combined (pile/stone columns) foundation system in soft soil is comprised. Furthermore, very extensive ongoing research work regarding the investigation and study on the performance of combined (pile/stone columns) foundation system in soft soils is discussed. The main goals and methodology to study the performance of the combined (pile/stone columns) foundation systems in soft soil are also addressed.

Determination of Subgrade Reaction Coefficients and Spring Stiffnesses for a Combined Pile Raft Foundation (CPRF) by Means of a Cluster Analysis

An analysis of combined piled raft foundations could be performed by means of a special geotechnical finite element software that utilizes 3D modeling and advanced constitutive models for the soil. However, a foundation is generally included in the structural models in a structural design program. The least advanced part of finite element software that has been developed for structural FEM modeling are the tools used for modeling behaviour. A method is required with which the input parameters of the structural design software that are used for modeling the soil structure interaction as well could be determined so that the results calculated by means of a geo-technical software that approximates realistic soil behaviour the best can be reproduced by structural design software as well. The procedure outlined in this paper by means of a cluster analysis provides a tool for a substantial and innovative improvement in subsoil modeling, to which not enough attention is generally paid in the structural FEM software, thereby resulting in a reduced amount of work associated with the task of inputting data.