西北干旱-半干旱区浅表层水（河流湖泊水、沟谷径流水、第四系砂层潜水等）,是维系区域生态地质环境（生态层）的珍贵水源,是煤层开采水资源保护的主体。根据区域浅表层水含隔水层地质结构,西北煤田煤层覆岩之上广泛分布新近系N2红土,为浅表层水底部的直接隔水层或沟谷径流的下垫层,对区域保水采煤、生态环境保护,起到至关重要的作用,是关键隔水层。在分析N2红土区域分布特征、基本物理-水理-力学性基础上,采用N2红土采动破裂钻孔原位压水试验、蠕变渗透性测试、水-土相互作用试验等,对N2红土不同程度采动破裂前后及其采后应力恢复蠕变的隔水性能变化特征进行了深入研究分析,发现N2红土隔水性能受采动破坏后,具有很好的自我恢复功能,并从其地质结构组成、水-土相互作用及其流变特性方面,解释了隔水性自然恢复机理;由此提出隔水层再造及其应具备的主要工程地质属性。

In the arid-semiarid area of northwest China,the shallow water such as the water of rivers and lakes,valley runoff water,the phreatic water of Quaternary in sand-layer and so on are precious water resources which maintain re- gional ecological geological environment and the body of water resource protection in coal mining. According to the re- gional geological structure of the shallow water aquifer-aquifuge,the N2 laterite,distributed widely above coal seam in northwest coal field of China,as the direct aquifuge bottom of regional shallow water or valleys runoff cushion,playing a crucial role to the coal mining with water protection and ecological environment protection,is the key aquifuge soil. In this paper,based on the analysis of regional distribution features,the basic physical,hydro-physical and the me- chanical properties of N2 laterite,the impermeability of post-mining stress recovery creep,before mining crack and post mining was deeply studied and analyzed by the water pressure test before and after mining,the test of creep permeabil- ity and the experiment of soil-water interaction and so on. The results show that the N2 laterite has a good capacity of self-recovery after the impermeability was broken by mining crack. The mechanism of impermeability self-recovery was explained from the perspective of geological structure,soil-water interaction and rheological properties;and according to this finding,the reconstruction of aquifuge and major engineering geological properties included was proposed.