Analysis For Deformation Mechanism And Nonlinear Consolidation Of Gravel Pile Composite Foundations

China is a country with a vast territory and complex geological condition. The soft soil is widely distributed in the inland and coast areas of China. Gravel pile is widely used in the soft soil foundation treatment because of its convenience, simple construction and low cost. Gravel pile also can greatly improve the bearing capacity of soft soil foundation and speed up the drainage consolidation of soft soil. Accurate and reasonable analysis of the deformation and consolidation are very important to control the deformation of the soft soil foundation. Despite the development of deformation and consolidation theories of gravel pile composite foundation discussed by many scholars, many deficiencies exist in engineering practices and its theories need further improvement.First of all, based on the stress field characteristics, displacement field characteristics of gravel pile composite foundation has been analyzed, and the vertical deformation mechanism and the radial deformation mechanism has been further studied. The commonly used methods of deformation analysis of gravel pile composite foundation have been researched and a settlement calculation method considering the bulge deformation is proposed.Secondly, on the basis of the past research and introducing the soil semi-logrithmic model of the e-lgσ’ of compressibility coefficient of soil and the e-lgk of permeability coefficient, the gravel pile composite foundation consolidation nonlinear differential equations are established and the nonlinear consideration analytical solutions are obtained, which consider the consolidation compression deformation of gravel piles and well resistance effects, disturbance and stress concentration effect. The comparative analysis between engineering examples and existing analytical solution shows that this method has preferable rationality and feasibility, and it is even more appropriate when the permeability coefficient of gravel pile is small(ie, gradation of gravel is well). Meanwhile, all kinds of factors that affect the average degree of consolidation of gravel pile composite foundation are analyzed.Finally, considering load in practical engineering are often change over time, a gravel pile composite foundation consolidation differential equations, which considering the deformation of the gravel pile, and the corresponding analytical solution are obtained. Under single ramp loading, the rationality and feasibility of this method was verified by engineering examples and existing analytical method, and the load duration Th0 the influence of the gravel pile composite foundation consolidation process was analyzed.