This study builds up an elliptical cylindrical equivalent model (ECEM) of prefabricated vertical drains (PVD)-improved foundation which incorporates the nonlinear variation of compressibility and permeability and the preconsolidate state of soil. An exact solution and a simplified solution are derived for the nonlinear consolidation model under a combined vacuum and surcharge preloading. Considering the stratification of improved soil and the reduction of vacuum pressure along PVD, a precise settlement prediction method is proposed. The rightness and applicability of present solutions are verified by carrying out a series of comparative analyses. Also, a parametric study is conducted to investigate the characteristics of nonlinear consolidation under different $N_{\mathrm{σ}}$, $C_{\mathrm{c}}/C_{\mathrm{k}}$, over-consolidation ratios (OCRs). The results show that, when $C_{\mathrm{c}}/C_{\mathrm{k}}=1$ the applied load has no impact on the dissipation of excess pore-water pressure, whereas a larger applied load would induce a quicker settlement rate; the consolidation rate would be underestimated if the over-consolidated stress history is neglected, and greater OCR produces more obvious underestimation.

中文翻译：

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基于椭圆柱等效模型的预制竖向排水沟改善软基非线性固结

本研究建立了预制垂直排水沟 (PVD) 改进地基的椭圆圆柱等效模型 (ECEM)，该模型结合了压缩性和渗透性的非线性变化以及土壤的预固结状态。推导出了真空和超载联合预压下非线性固结模型的精确解和简化解。考虑到改良土的分层和沿PVD的真空压力降低，提出了一种精确的沉降预测方法。通过一系列对比分析，验证了现有解决方案的正确性和适用性。此外，还进行了参数研究，以研究不同条件下非线性固结的特性。$N_{菅}$, $C_{\mathrm{C}}/C_{\mathrm{克}}$, 过度整合率 (OCR)。结果表明，当$C_{\mathrm{C}}/C_{\mathrm{克}}=1$外加荷载对超孔隙水压力的消散没有影响，而外加荷载越大，沉降速度越快；如果忽略过度固结的应力历史，固结率将被低估，而更大的 OCR 产生更明显的低估。