水力梯度作用下填埋场压实黏土盖层开裂失效机理研究

The cracking failure of compacted clay cover is one of the main causes which make landfill catastrophe and the surroundings polluted. With the gradient distribution of water content in cover as external drive leading to the inhomogeneous deformation in clay, the shrinkage in clay due to water loss is the internal essence of cracking failure. In order to show the clay crack mechanism, it is of great significance to research the influence of hydraulic gradient on the crack in clay cover. Aiming at showing the main factor and internal mechanism in the formation process of clay cover crack deeply and providing theoretical guidance and technical support for the optimal design of new cover system and crack prevention of landfill clay cover, the project intends to use multi-disciplinary theory and method including unsaturated soil mechanics, seepage mechanics, fracture mechanics, environmental geotechnical engineering, etc . Through landfill-compacted-clay-cover model experiment under hydraulic gradient, mechanics-seepage element experiment and microstructure experiment, the project reveals the mechanics character, permeation mechanism and crack mechanism of compacted clay cover under hydraulic gradient on macro- micro multiple scales, establishes crack drive evolution model of landfill compacted clay cover under hydraulic gradient and quantitatively analyses the dynamic law of crack formation, development and evolution in compacted clay cover.

填埋场压实黏土盖层开裂失效是致使填埋场灾变与周边环境污染的主要原因之一。压实黏土开裂失效归因于黏土失水收缩这一内在本质，其外在诱因为盖层内部含水率梯度分布致使黏土非均匀变形。探究水力梯度对压实黏土层开裂的影响对揭示压实黏土干缩开裂机理具有重要意义。本项目拟应用非饱和土力学、渗流力学、断裂力学、以及环境岩土工程等多学科交叉的理论和方法，通过开展水力梯度作用下填埋场压实黏土盖层相似模型体试验、力学-渗透特性单元体试验以及微观结构特性试验研究，从宏-微观多个尺度揭示水力梯度作用下压实黏土盖层的力学特性、渗透机理以及开裂机制，建立水力梯度作用下填埋场压实黏土盖层开裂动力演化模型，定量分析在水力梯度作用下压实黏土盖层裂隙发生、发展和演化的动力学规律，从机理上深入揭示影响黏土盖层开裂过程的主控因素和内在机制，为填埋场粘土盖层开裂失效防治和新型覆盖系统的优化设计提供理论指导与技术支持。

压实黏土盖层开裂失效是致使填埋场灾变与周边环境污染的主要原因之一。本项目基于自主研制的填埋场盖层失效模型试验装置，开展了填埋场外部干湿交替与内部高温环境等灾变因素对压实粘土盖层宏-微观结构影响规律研究，提出了以含水率梯度作为压实粘土层开裂的判断因子，获得了压实粘土裂隙随含水率梯度的统一变化规律，建立了含水率梯度作用下填埋场顶部防渗系统开裂失效分析模型。基于压实粘土含水率梯度调控思想，研发了固体废弃物填埋场生态防渗与修复技术（获批省级工法），已成功应用于三峡库区13座磷废渣填埋场治理工程中，取得了良好经济与环境效益，为我国固废填埋场封场覆盖系统失效分析、优化设计以及失效防控提供了理论与技术支持。研究成果本项目共发表SCI论文9篇，出版专著1部；主编省级工法规范1部，参编省级工法1部；申请发明专利4项，登记软件著作权2项；获得2016年湖北省科技进步一等奖，2018年中国技术市场金桥奖项目突出贡献奖。