饱和砂土中泥浆渗透的变形-渗流-扩散耦合计算模型

A DEFORMATION-INFILTRATION-DISPERSION COUPLING MODEL FOR THE SLURRY INFILTRATION COMPUTATION IN SATURATED SAND

传统的泥浆渗透计算中没有考虑土体变形和浆液流速的影响.根据泥浆颗粒的质量守恒定律推导了耦合流速的浓度扩散方程,并通过在浓度方程中引入沉积系数进一步计算得到沉积颗粒的质量;同时,以沉积量作为耦合项对毕奥固结方程中的水量连续方程进行了修正,在此基础上建立了变形-渗流-扩散耦合的控制方程及其变分原理.采用有限单元法求解基本方程,运用了时间增量法与直接迭代法,并利用一维试验验证计算方法的可靠性,并与赫齐格的经典模型的计算结果进行了比较,结果表明,本文建立的模型的计算结果可以较好地预测各组试验中颗粒的沉积规律,且吻合程度优于仅考虑颗粒对流和扩散的传统计算方法.最后,将泥浆在槽壁中的渗透简化为二维问题并进行了计算,计算结果与工程认识相符合,泥浆的沉积填充效应随深度的增加而增大,施工时需要严格控制浅层作业段的机械垂直度;成槽机的下斗抓挖时机可以根据地层填充的致密程度进行计算,对现场施工具有一定的指导意义.

Soil deformation and water seepage are ignored in the computation of slurry infiltration in traditional method.In this paper, the particle dispersion equation coupled with seepage velocity is derived according to the particle mass conversation, which highlights the dynamic properties of the suspended particles transport and deposition. The continuity equation for the suspension is proposed by modifying the water continuity equation in Biot＇s consolidation theory considering the effect of particle deposition in slurry. Based on this, non-linear governing equations for slurry infiltration coupling deformation, infiltration and dispersion are derived and the corresponding variational principles are established.Finite element model based on the principles is established and the equations are solved with both incremental and iterative techniques. Computational results are validated by predicting the data from one-dimensional model test, and better agreement with the experimental data is shown compared to the traditional method which only considered particle convection and dispersion. The slurry infiltration in slurry trench is calculated with the method proposed in this paper. The deposition amount of slurry particles grows with the increasing depth, which indicates that a strict vertical degree control is needed during the shallow slurry trench construction. The excavating schedule can be determined considering the filled extent by the slurry particles according to the computation.