污染泥堆场处置中自重固结与污染物迁移的耦合分析

Coupled analysis of self-weight consolidation and contaminant transport in confined disposal of contaminated sediments

基于一维固结方程和对流-弥散方程,提出了一种用于污染泥堆场处置中自重固结与污染物迁移耦合问题的求解方法,其中,自重固结方程由解析解直接求解,污染物迁移方程由显示差分法求解。在自重固结方面,新方法可考虑线性的压缩关系和渗透关系;在污染物迁移方面,新方法能够考虑对流、扩散、机械弥散、线性和非线性吸附以及孔隙率相依的有效扩散系数。新方法与CST1数值模型进行了对比,验证了新方法的正确性。基于所提出的解,分析了固结效应、压缩系数、渗透系数和污染物初始分布形式对污染物在淤泥中迁移过程的影响。计算结果表明:固结效应、压缩性、渗透性和污染物的初始分布形式对污染物的迁移过程有着显著的影响;固结效应能显著地加速污染物的流出;土体的压缩系数越大其污染物累计流出质量越大;土体的渗透系数越大其污染物累计流出质量越大;污染物的初始分布形式对污染物的流出速率影响较大。

Based on the one-dimensional (1D) consolidation equation and advection-dispersion transport equation,this paper presents a solution for coupled self-weight consolidation and contaminant transport in confined disposal of contaminated sediments.The explicit finite difference method is used to solve the transport governing equation,whereas the analytical solution is used to solve the self-weight consolidation equation.In terms of contaminant transport,the proposed solution accounts for advection,diffusion, mechanical dispersion,linear and nonlinear equilibrium sorption,and porosity-dependent effective diffusion coefficient.The proposed numerical solution is compared with the CST1 numerical model to verify its correctness.Using the verified solution,a series of parametric study is conducted to investigate the effects of several important parameters (i.e.,consolidation effect,soil compressibility and permeability,and initial contaminant distribution) on the contaminant transport process in the confined disposal of dredged contaminated sediment.The results indicate that the consolidation effect,soil compressibility,soil permeability and initial contaminant distribution have significant impacts on the contaminant transport process in confined disposal of contaminated sediments.Consolidation can greatly accelerate the contaminant transport rate.The contaminant cumulative mass outflow increases largely with increasing compressibility coefficient and permeability coefficient.The rate of contaminant transport is considerably affected by the initial contaminant distribution.