针对填埋场复杂水化环境对封场覆盖系统长期性能的影响，以膨润土-红粘土混合土覆盖材料为研究对象，通过先进的系统试验和数值模拟，深入研究干湿-化学耦合作用下混合土覆盖系统的致裂机理，分析裂纹扩展对覆盖系统防渗及水-气运移性能的影响规律。通过自主设计的“带载水-气运移一体仪”，进行污染物运移、水-气渗透和干湿循环试验，查明混合土覆盖材料中水-气运移特性；研制温-湿控制土体裂缝扩展观测模型箱，考察干湿-化学耦合作用下混合土体裂纹孕育及扩展过程，揭示干湿-化学耦合作用对混合土体致裂的影响机理；结合水银孔率计、微观CT扫描技术（μCT）等微观结构测试，考察混合土体致裂过程中微观结构调整。在此基础上，构建裂纹扩展模型，模拟干湿-化学耦合作用下混合土体裂纹扩展行为；建立致裂后混合土体中污染物的迁移-扩散和水-气运移模型，分析裂纹扩展对混合土覆盖系统化学-水力性能的影响，评估混合土覆盖系统的长期安全性。

In order to study the effects of complex hydro-chemical coupling environment on long-term performance of landfill soil cover system, the bentonite-laterite mixture is considered as for soil cover system material. A serial of advanced experiments and numerical simulation will be performed on mixture material, the cracking mechanism of the mixture cover system induced by wetting/drying-chemical coupling will be studied, and the influence of crack propagation on the water infiltration and gas migration behavior will also be analyzed. Firstly, the laboratory experiments including penetration and contaminant migration, wetting and drying test, and gas migration test will be fulfilled to investigate the water infiltration and gas migration properties of the mixture cover system using the designed ’Water-air transport instrument’. Secondly, a soil cracking propagation observation box will be developed to observe cracking process of the mixed cover system induced by wetting/drying-chemical coupling, and then the influence mechanism of wetting/drying cycle and chemical gradient on the cracking will be revealed. Lastly, microstructure tests such as mercury intrusion porosimetry (MIP) and microscopic CT scanning technique (μCT) will be carried out on the specimens which will have undergone the hydro-chemical coupling testing in order to analyze the microstructural cracking mechanisms. Based on the experimental results, a crack propagation model will be established to study the cracking propagation behavior of the mixture cover system under the wetting/drying-chemical coupling effect; subsequently, the migration-diffusion of the contaminant, water infiltration and gas migration model in the cracked soil cover system will be established to simulate the effects of crack propagation on the chemo-hydro behavior of the mixture soil cover system, and then to assess the long-term safety of this material used as cover system of a landfill.