Analytical solution for consolidation of combined composite foundation reinforced with penetrated impermeable columns and partially penetrated permeable stone columns

摘要

The combination of composite foundation with permeable and/or impermeable piles can promote the consolidation process of soft soil. This can enhance the strength of foundation, and has a great practical value for the treatment of soft ground. Based on an axisymmetric consolidation model and the consolidation theory for double-layer ground, the consolidation characteristics of combined composite foundation reinforced by penetrated impermeable columns and partially penetrated permeable columns have been studied. A differential equation, subjected to an instant load, has been established, considering the volume change of the permeable columns. Its analytical solution agrees well with the solutions obtained by using finite element models. Additionally, the main factors influencing the consolidation rate of the combined composite foundation have been analyzed, and the results indicate that the consolidation can be accelerated significantly by lengthening the permeable columns. The consolidation rate increases with increasing the replacement ratio and the permeability and compressive moduli of the soil and columns. For the same conditions, the increase of consolidation rate caused by enlarging the compressive modulus of the upper improved soil is less than that caused by enlarging the compressive modulus of the lower improved soil, while the permeability of the soil has the reverse effect.