Nonlinear analysis for consolidation of soft soils improved by composite piles with stiff core and gravel shell

The implementation of composite piles has emerged as an appealing technology for reinforcing soft ground through fulfilling the requisite bearing capacity and facilitating consolidation. Nonetheless, previous investigations into the consolidation behavior of composite pile-improved ground have neglected the nonlinearity of soil compression and permeability. In this context, the logarithm models of e-lgcr and e-lgk are introduced to establish an analytical model for the nonlinear consolidation of composite ground with composite piles. Based on equal strain assumption and annular equivalent method, detailed solutions under four special loading schemes are then obtained. Additionally, a comprehensive analysis is conducted to assess the influence of various parameters on the nonlinear consolidation behavior of composite ground, and the feasibility of current model is verified by degenerations. The results show that ignoring the nonlinearity will lead to an overestimation of consolidation rate when the soil's compression indices exceed the permeability indices. Moreover, the consolidation rate of composite ground is inversely proportional to cru/cr ' s0 and Cc/Ckh(v), while demonstrating a direct proportionality to Ksp, Ksg, and kg/kv0. However, cru/cr ' s0 mainly influences excess pore water pressure at the upper layer, and the influence of Cc/Ckv on the consolidation rate is limited and can even be ignored in comparison to Cc/Ckh. Finally, the proposed model is successfully applied to an engineering project in situ, where the obtained results exhibit a noteworthy agreement with the measured data.