Reconstructed water-blocking layer in open-pit mine and the damage-permeability characteristics of mudstone-geopolymer

The major environmental problem in open pit coal mining is water conservation and restoration,which re- stricts the large-scale development of open pit mines. The surrounding groundwater resources are severely damaged by the funneling effect formed in mining process,which is difficult to recover. The reasons are demonstrated as follows:the water-blocking layer above coal seam is missing due to stripping;the material loose in structure in the inner dump is characterized by a large permeability,which does not achieve the effect of water blocking. At present,there is little sys- tematic research and effective measures for restoring and maintaining open-pit mine water resources. This paper propo- ses a reconstructed water-blocking layer based on mudstone polymer composed by the solid wastes in open-pit mines and surrounding industrial areas. With the realization of the construction of the water-blocking layer,a large amount of industrial waste is consumed, forming an industrial ecosystem centered in open pit mines. Low permeability within 10-15 m2 is the basic feature of the water-blocking material. Alkali-inducing powder materials (Mudstone,slag and red mud), fine aggregate material ( standard sand), and activator ( sodium silicate ) were used to prepare standard (ϕ50 mm×100 mm) mudstone-geopolymer samples. The damage permeation characteristics of materials are investiga- ted in this research. The damage variable Dσ is measured by uniaxial loading. The permeability characteristics under different damages are analyzed through experiments. The results show that under low damage (σ / σc