参考网格映射井壁边界修正下考虑时变井阻与真空深度衰减的真空预压数值模型研究

    Numerical modeling of vacuum preloading incorporating time-dependent well resistance and depth-attenuated vacuum with a reference-grid-mapped well-boundary correction

    • 摘要: 针对真空预压条件下软土地基固结现有理论难以同时表征涂抹效应、排水板通水能力随时间退化引起的井阻变化以及真空压力沿深度非均匀传递等问题,基于单井单元体概念建立二维轴对称固结模型,在控制方程中同时考虑径向与竖向组合渗流;采用分段径向固结系数描述涂抹区渗透性降低;将真空压力沿排水板深度的线性衰减作为井壁负孔压边界条件;并引入排水板渗透系数随时间指数衰减的时变井阻模型以刻画淤堵退化。针对显式有限差分求解中井壁Robin边界对网格尺度敏感的问题,提出参考网格映射的网格无关性修正方法,提高边界通量的数值一致性与结果鲁棒性。在以上海迪士尼乐园典型真空预压试验区为例的工程验证中,模型沉降预测与实测曲线吻合良好,能够合理反映孔隙水压力的径向传递与消散过程,相较传统简化解析解对中后期固结固结速率降低特征具有更好的解释能力。参数敏感性分析表明,井阻退化显著延缓固结进程并增强后期固结速率降低现象;涂抹效应对整体平均固结度影响相对较低但对近井区早期排水具有局部控制作用;忽略真空度深度衰减易高估深部有效应力增量与最终沉降。研究成果可为真空预压排水板地基处理的参数反演、效果评价与设计优化提供参考。

       

      Abstract: Existing consolidation for soft soil ground improved by theories on vacuum preloading often fail to simultaneously account for the smear effect, time-dependent well resistance degradation due to clogging, and non-uniform vacuum pressure transmission along depth. To address these limitations, this paper develops a two-dimensional axisymmetric consolidation model based on a single-well unit cell. The governing equations incorporate coupled radial and vertical flow, utilizing piecewise radial consolidation coefficients to describe the smear zone and a linear decay of vacuum pressure along the drain depth. A time-dependent well resistance model, defined by the exponential decay of drain permeability, is introduced to characterize clogging. Furthermore, a reference grid mapping method is proposed to correct the mesh sensitivity of the Robin boundary condition in the explicit finite difference solution, thereby enhancing numerical robustness. Validated against field data from the Shanghai Disney Resort, the model demonstrates high accuracy in predicting settlement and pore water pressure dissipation. It outperforms traditional simplified analytical solutions in characterizing the deceleration of consolidation rates during the middle and late stages. Sensitivity analyses indicate that well resistance degradation significantly retards the consolidation process, while the smear effect primarily controls early-stage drainage near the well but has a limited impact on the overall average degree of consolidation. Additionally, neglecting vacuum attenuation along depth tends to overestimate deep effective stress and final settlement. These findings can provide a valuable reference for parameter back-analysis, effect evaluation, and design optimization in vacuum preloading projects.

       

    /

    返回文章
    返回