An Analytical Solution for the Deformation of Soft Ground Reinforced by Columnar Inclusions under Equal Stress Conditions

Abstract

Columnar inclusion is a versatile and cost-effective technique for improving weak soils. Currently, most approaches are based on the “equal strain” assumption to calculate the deformation of soft ground reinforced by columnar inclusions. In this study, a new model to simulate the behavior of column-reinforced soft soil under equal stress conditions based on the variational principles is proposed. The proposed model satisfies the force equilibrium and deformation compatibility simultaneously, which is seldom fulfilled in traditional empirical methods or other analytical models. The corresponding analytical solution is obtained and its accuracy is verified by comparing it with the numerical solutions using finite element analysis. The comparisons of the proposed solution with an existing solution show that the proposed solution can provide very close agreement over a wide range of parameters while the existing solution is only able to provide a reasonable agreement for a certain range of stiffness ratio of the column and soft ground. In addition, a parametric study is made to illustrate the influence of various parameters on ground settlement predictions. The parametric study indicated that, by increasing the ratio of elastic modulus between the stone column and surrounding soils and the ratio between the radius of the stone column and the space of the stone column, the load transfer effect has been significantly improved, and the ground settlement becomes smaller. Furthermore, the Poisson’s ratio of the surrounding soil also has a very significant effect on ground settlement, while the effect of the Poisson’s ratio of the stone column on ground settlement is less significant compared with that of the surrounding soil.