生活垃圾优先流特性及其对填埋场水分运移的影响研究

Many problems in municipal solid waste (MSW) landfill are caused by water or leachate and its movement. The prevailing approach for modeling water flow processes in MSW is based on the assumption of a homogeneous porous media, and cannot reflect the macroporous nature of MSW. Taken MSW as a heterogeneous porous material composed of a channel domain and a surrounding matrix domain, unsaturated flow and channel flow are considered in this program to study the water movement in MSW. A series of MSW column leaching test and dye tracing test will be carried out to investigate character of macropore and channel flow in MSW. Water holding capacity and unsaturated permeability of MSW will be examined by field and laboratory tests. Based on concept of preferential flow, a two-domain model will be used to simulate the water movement and distribution in MSW. Model test will be conducted to check the two-domain model. Considering preferential flow, pattern of leachate production, contaminant transport, leachate recirculation and leachate drawdown analysis will be carried out and corresponding proposal to project will be given. This program is helpful to safe operation of landfills and will contribute to prevention of environmental problems. At the same time, this research is of theoritical significance in further developing preferential flow theory and promoting the intersection of Geotechnical, Hydraulic and Environmental Engineering.

生活垃圾填埋场若干关键问题都与填埋场中的水（渗滤液）及其运移有关。对于渗滤液运移，目前一般将垃圾视为具有一定渗透系数的均质体进行研究，未能反映垃圾大孔隙特性。本项目将垃圾视为由基质和大孔隙组成的非均匀多孔介质，结合非饱和流与大孔隙流理论，研究垃圾中水分运移规律。通过一系列的垃圾柱出流试验和染色示踪试验研究垃圾大孔隙特征和大孔隙流规律；通过室内和现场试验研究垃圾的持水与非饱和导水特性；基于优先流理论与非饱和渗流理论，建立大孔隙和基质两域模型模拟垃圾中水分运移与分布；通过模型试验进一步揭示垃圾中优先流规律并对两域模型进行验证；使用两域模型模拟填埋场渗滤液产出、污染物迁移、渗滤液回灌和填埋场抽排降水等水分运移过程，揭示相应规律，提出工程建议。本项目研究对填埋场安全运营和污染防治具有实际意义；对于进一步揭示大孔隙介质优先流机理，促进岩土、水利与环境工程的学科交叉，具有重要理论意义。

生活垃圾填埋场若干关键问题都与填埋场中的水分运移有关。生活垃圾成分复杂，垃圾中同时存在细粒基质和大孔隙，以大孔隙流为特征的优先流是垃圾中水分和溶质运移的重要方式。本项目以室内试验为主，结合理论分析和数值模拟，将垃圾视为由基质和大孔隙组成的非均匀多孔介质，基于非饱和土理论与优先流理论，揭示垃圾中的优先流机理和特征，研究垃圾中水分运移规律。现场取不同埋深垃圾试样进行室内试验研究了生活垃圾持水特性和非饱和导水特性；基于完整土-水特征曲线确定了垃圾的孔径分布，通过核磁共振试验测试了垃圾孔径分布，两种方法均揭示了垃圾具有大小双重孔径分布特征；进行垃圾优先流特征的染色示踪试验，研究了入渗强度、初始含水率、不同埋深对垃圾优先流的影响规律；进行溶质出流试验，使用对数正态分布模型和双峰概率密度模型对出流曲线进行回归分析，得到各因素对垃圾优先流的影响规律及两域模型相关参数；建立两域模型模拟垃圾中水分运移，探讨了两域模型和非饱和渗流模型的适用条件；使用非饱和土柱的对流-扩散装置，研究了非饱和土中污染物迁移机理；试验研究了优先流加快污染物迁移的机理和规律。结合本项目共发表论文10篇，其中SCI或EI收录9篇，国际会议论文1篇。