Analytical Solutions for Radial Consolidation of Soft Ground Improved by Composite Piles Considering Time and Depth-Dependent Well Resistance

Composed of a stiffer core with gravel shell, composite pile is a new pile technology with a variety of shapes and sizes to improve soft soils. Compared with piles with single materials, composite ground improved by composite piles avoids some drawbacks with slow consolidation and limited increase in load bearing capacity. After converting unit cells with noncircular composite piles into cylindrical ones using an annular conversion method, based on an equal strain assumption and the hypothesis that water volumes flowing into and out of the gravel shell are equal, an analytical model is proposed to investigate consolidation characteristics of soft ground improved by composite piles. Furthermore, the hypothesis that the discharge capacity of the composite pile is exponentially decreased with time owing to clogging, and linearly varied with depth is employed in the derivation. In addition, detailed solutions subjected to an instantly applied load are obtained using a Bessel function, and the degeneration of this answer is calculated to verify its accuracy. Then, some comparisons between this method and previous studies including mathematical methods and a case are made to verify the feasibility and applicability of the presented solution. Finally, a parametric study is conducted to find detailed effects of time-dependent clogging and depth-dependent well resistance on consolidation. The results show that consolidation rate is proportional to B1, while it is negatively correlated with B2, α3, and H.