Experimental study on reconstruction material of impervious layer in open-pit mine external dump in arid area

Xinjiang has huge reserves of coal resources and has the conditions and advantages to develop and construct large-scale open-pit coal mines. However, due to the climate characteristics of Xinjiang’s arid areas, open-pit mining has a wide range and high degree of impact on the ecological environment and damage. It is of great practical significance to carry out ecological restoration of open-pit mines in arid areas. Due to the loose materials, high porosity and permeability of the waste dump, the ecological restoration of the waste dump in arid areas is a serious challenge. In order to solve the shortage of water resources in the ecological restoration process of open-pit coal mines in the arid areas of western China, improve the ecological restoration effect of open-pit coal mines in the arid areas, based on the dual technical objectives of material strength and permeability, explore and reconstruct the material ratio of the impervious layer of the open-pit mine external dump, carry out relevant research with different material ratio schemes using indoor permeability test and uniaxial compressive strength. The main composition, uniaxial compressive strength and permeability of the materials with different proportions were determined by XRD diffraction test, uniaxial compression test and variable head permeability test, and the material proportioning parameters of the reconstructed aquiclude were studied. The test results show that the compressive strength of the specimen increases by 22% when the curing agent ratio increases by 2%, but the increasing trend starts to decrease when the curing agent ratio exceeds 8%. When the curing agent ratio increases from 8% to 10%, the compressive strength of the specimen increases by only 6%. With the increase of fly ash content, its permeability decreases gradually. Every 2% increase of fly ash content can reduce the permeability of 28%. The following rules are obtained: the influence of the content of curing agent on the compressive strength of the specimen is greater than that of the fly ash content, and the influence of the fly ash content on the permeability is higher. When the fly ash content is fixed, the curing agent content is positively correlated with the uniaxial compressive strength of the specimen. When the ratio of curing agent is fixed, the uniaxial compressive strength of fly ash increases with the increase of the ratio.