考虑填埋场沉降和生物降解作用下的孔隙度仿真预测研究

垃圾填埋场上覆层的压缩以及自身的降解作用使内部孔隙结构发生了改变。沉降和生物化学反应的双重作用改变了填埋场原有孔隙度分布。将垃圾压缩变形和微生物降解所引起的产气过程相结合，建立了描述填埋场孔隙度-位移-气体压力相互作用的耦合数学模型，并给出了耦合模型的数值格式。通过数值计算得到了垃圾填埋体的沉降应变、孔隙度、孔隙渗透及扩散特性的变化规律。计算结果表明，填埋场运营前10年垃圾降解对孔隙度作用较明显，孔隙度呈线性增大，随后增大幅度减缓，达到峰值后逐渐减小，减小过程主要受垃圾沉降作用影响；不同成分的有机质含量对孔隙度的影响也存在差异；受有机质降解作用的影响，填埋约为190个月时固有渗透率可达到1.4 10-12 m2，Dg/D0可达到0.178。因此，开展填埋场沉降和生物降解作用下孔隙度的预测研究，对于评价填埋气体的有效控制以及填埋场安全指标体系的完善都具有重要的现实意义。

Numerical prediction of settlement and biodegradation effect on porosity within landfill

The obvious change of the inner pore structure as a result of overburden waste compression and itself organic decomposition in landfill. Biodegradation and its-induced settlement is a direct result of rearrangement of waste porosity. The coupling model has been developmented to describe the interacting of porosity-displacement- gas pressure with combine to the waste deformation and micro-biological degradation. And the numerical scheme of the model is given. The settlement strain and porosity and permeability and diffusivity are obtained by numerical simulation. The results show that the obvious change of porosity with the effect on degradation in early 10 years. The porosity increased almost linearly. Later, the increasing amplitude is slowly, and drop is started after peak point. The waste settlement is the key to the decrease process of porosity. The variant effect of organism content on porosity is different. The permeability increased to 1.4 10-12 m2 and Dg/D0 increased to 0.178 by organic decomposition in the dispose duration. There is a important practical significance in predicting porosity with landfill settlement and biodegradation for the evaluation of LFG effective control and complete safe index system of landfill.