填埋场热生成及对垃圾堆体和防渗衬垫变形强度特性影响机理

The proposed project will be carried out the key scientific researches regarding organic degradation, temperature changes and influences in landfill. Based on the high organic content and water-sensitive characteristics of thermal conductivity for the municipal solid waste (MSW), the production source term(leachate, gas, heat) equation will be established by conducting degradation experiments to reveal heat conduction and degradation mechanisms of the MSW. Based on the heat transfer characteristics of the MSW, organic degradation of the production source term, the energy conservation equation, and fluid deformation constitutive equations for unsaturated soils, the differential equations of coupled transport will be developed to investigate variations of internal temperature and fluid pressure in landfill. Under different temperatures, the stages of compression and temperature sensitivities of the primary and secondary compressions as well as degradation deformation will be studied by conducting waste deformation. A mechanical model of complex stress paths will be developed by trixial tests of stress path including temperature influences. A large torsional shear apparatus will be used to investigate the interface shear strength properties of landfill composite liner systems under temperature impact. The investigation will focus on the transfers of failure interface in composite liner systems and the interface and internal properties of large deformation or residual shear strengths for geosynthetic liner materials. A new landfill slope stability analysis method will be established by considering the influences of temperature and fluid pressures. The applications of the proposal expect to obtain some major achievements in the aspects of MSW heat conduction properties and degradation production source term theory, fluid migration theory and pressure variations, waste deformation and strength characteristics, liner interface strength properties and slope stability analysis theory.

申请项目将开展垃圾填埋场有机物降解、温度变化与影响的关键科学问题研究。基于垃圾土高有机质含量和热传导水敏感特性，通过降解试验建立产源项(产气、产液、产热)方程，揭示垃圾土热传导机理和降解机制；依据垃圾土热传导特性、有机物降解产源项、能量守恒方程、非饱和土流体变形本构方程，建立耦合运移微分方程组，调查填埋场内部温度和流体压力的变化规律；进行不同恒定温度下垃圾土变形特性试验，研究主次压缩和降解压缩变形的阶段性和温度敏感性规律，利用应力路径三轴试验发展温度影响下复杂应力路径的力学模型；利用大型扭剪设备，开展温度影响下复合衬垫界面剪切特性研究，重点调查复合衬垫的剪切破坏面转移和残余强度变化规律；建立考虑温度、流体压力影响的垃圾体边坡稳定分析方法。申请项目期望在垃圾填埋体热传导特性与降解产源项变化理论、流体运移理论与压力变化规律、垃圾土变形和强度特性、衬垫界面强度特性与边坡稳定分析理论取得重点突破。

项目申请当年我国生活垃圾清运量19141.9万吨，运行垃圾填埋场640座，填埋场失稳事故时有发生且无法预测控制。项目执行期间开展了系列填埋场大型现场试验、生物反应器试验、单元降解反应试验和耦合运移理论建立、计算分析、机理揭示研究，解决了填埋场有机成分降解热生成、热传导、热影响、热利用中基础理论和工程应用问题。对应科学问题一，完成了液-气-热耦合运移理论建立、产源项的试验方法研制、模型参数确定，进行了生物反应器试验、填埋场大型现场试验的验证和预测，揭示出填埋场热运移规律，提出了填埋场热利用控制准则；对应科学问题二，进行了控制温度的垃圾土和衬垫界面剪切变形强度试验，得到了温度变化影响下垃圾土和界面变形强度规律；开展了温度影响下污染物在衬垫中的运移理论和规律研究，发现了温度对污染物在衬垫中运移的作用特性；建立了考虑温度和垃圾气压力影响的填埋场边坡稳定分析方法，在中国无锡、美国Ohio等多个实际工程分析中得到应用，为填埋场安全运行提供有力理论支撑。项目在填埋场液-气-热耦合运移理论建立和产源项试验技术研制取得创新性，在垃圾土和衬垫界面受温度影响的强度变形规律以及填埋堆体稳定预测控制方法上取得突破，提出的填埋场热调节和利用关键控制方法得到了国际同行认可和采纳；推动国际填埋场降解产热问题理论研究和实际应用实质性进展。耦合理论的产源项试验和计算方法简单，既完备了耦合理论，又实现了参数与政府间气候变化组织推荐的美国环保协会EPA模型参数的相互换算，使土木工程和环境工程专业在垃圾土有机成分降解计算上达成完全融合；提出了填埋场考虑气压力和温度升高影响的边坡稳定计算方法，我国填埋场高淋滤液水位条件下产气量和渗透系数确定方法保证了预测填埋场边坡稳定的合理性，实现填埋场边坡稳定控制标准与现行规范控制要求的高度匹配；填埋场热调节和利用的试验方法为美国加州大学圣地亚哥分校同类试验复制，采用的试验周期等关键控制方法亦为该机构采信。