Analytical Theories Of Composite Foundations Improved By Geosynthetic-encased Columns

Geosynthetic-encased column (GEC) is one kind of new composite foundation type not only has typical composite foundation characteristic of the vertical enhanced body, simultaneously has the drained consolidation reinforcement effect. So it can become one more economical effective soft clay ground treatment method hopefully. In this paper, we receive GEC as the object of study, use the correlation theories of the space axial symmetry and establish the stress-strain analysis and the consolidation analytical theory of GEC. The result of this paper provides the scientific and reasonable method for the design calculation of GEC, and promotes this kind of composite foundation to be popularization and application. All the work done is as follows:Firstly, under the equal strain condition, based on all the materials are linear-elastic homogenous materials, the column-soil system on a smooth base and neglecting the weights of column and soils, we use spatial axial symmetry unit cell model which constituted by the column, geotextile and surrounding soils. Then using the deformation method and stress method, we receive the analytical elastic solution expression of the radial and vertical displacements and all stresses of the column and the soil, as well as that of hoop force of the geotextile encasement.Secondly, on the basis of the analytical solution for deformation, we establish the consolidation governing equations of the GEC in two kinds of operating conditions of instantaneous load and non-instantaneous load. Then applying the relevant methods of partial differential equations, we get the solutions of consolidation governing equations. So the analytical solutions of consolidation degree for the GEC are obtained.Finally, we detailedly analysis the working properties of the GEC by discussing the influence of the stiffness of geotextile, area replacement ratio, modulus ratio and other parameters on the deformation and consolidation problems of the GEC.The analytical theory of deformation and consolidation problems about GEC establishing in this paper is the more perfect more scientific. This paper banishes many hypothesis conditions which were used by the traditional theories; the rigorous analytical solution theory is advantageous to safeguard the scientific nature of reinforcement mechanism analysis of geotextile coated column-type composite foundation, the research results can provide reliable and reasonable design calculation method for hoop force and consolidation property of GEC.