Abstract
The water-blocking properties of the clay layer at the bottom of the Cenozoic overburden in China are an important factor influencing the safety of thin bedrock coal seam mining. Clay has remolding properties that are unlike the nonreversible characteristics of cracks in brittle rock, and failure cracks in clay can reclose or continue to expand under the influence of different external factors. In this work, the soil layer on top of thin bedrock is the research object, and the influences of the particle composition, water content, soil layer thickness, and crack width on the crack development-closure state of soil layer are analyzed by the orthogonal test method. Visual analysis shows that the order of influence of each factor on the stability of soil layer is the crack width, particle composition, soil layer thickness, and water content. The stability of soil layer decreases with increasing crack width and sand content and decreasing soil layer thickness; in addition, soil layer stability decreases first and then increases with increasing water content. Further variance analysis shows that the crack width and particle composition are key factors that impact the stability of soil layer and that the soil layer thickness has some influence, while the water content has little effect on the stability of soil layer. In addition, the crack will reclose when the sand content in soil is less than 50% and the crack width is less than or equal to 1.0 mm, and the soil layer is prone to further failure when the sand content in soil is more than 50% and the crack width is greater than or equal to 3.0 mm; when the soil layer thickness is 15.0 cm, its stability is better than when the soil layer thickness is 10.0 cm or 5.0 cm.
Highlights
Environmental problems, such as water resource shortages and surface degradation caused by coal mining, are becoming increasingly prominent as the intensity of coal mining in China increases. e aforementioned is especially true in midwestern areas, where underground latent water resources are widely distributed in the Cenozoic overburden
Four factors that affect the development-closure state of crack, namely, particle composition, soil layer thickness, crack width, and water content, are examined. e crack development-closure characteristics of soil layer are analyzed by the orthogonal test method. e aim of the work is to provide a reference for the stability analysis of overlying soil and the protection of underground latent water resources in thin bedrock geological regions during thin bedrock coal seam mining
Analysis of Experimental Results. e experimental results show that the crack will close when the sand content in soil is less than 50% and the crack width is less than or equal to 1.0 mm and the soil layer is prone to further failure when the sand content in soil is more than 50% and the crack width is greater than or equal to 3.0 mm. e experimental results preliminarily reveal that the greater the sand content and the wider the crack width and the smaller the thickness of the soil layer, the worse the stability of the soil layer, because the orthogonal test method is adopted instead of the comprehensive test method, and visual analysis and variance analysis are needed to get more accurate conclusions
Summary
Environmental problems, such as water resource shortages and surface degradation caused by coal mining, are becoming increasingly prominent as the intensity of coal mining in China increases. e aforementioned is especially true in midwestern areas, where underground latent water resources are widely distributed in the Cenozoic overburden. Ese ideas and methods have provided new ways of protecting underground latent water resources. E water flowing fractured zone usually penetrates through thin bedrock while mining coal seams under thin bedrock At this time, the clay layer at the bottom of the Cenozoic overburden becomes an important water-blocking structure and plays an important role in preventing the water in porous aquifers and phreatic aquifers from flowing to the working face [26]. E characteristics of crack development-closure in soil layer are of great significance to the stability of the overlying soil and its water-blocking effect in thin bedrock coal seam mining. E aim of the work is to provide a reference for the stability analysis of overlying soil and the protection of underground latent water resources in thin bedrock geological regions during thin bedrock coal seam mining Four factors that affect the development-closure state of crack, namely, particle composition, soil layer thickness, crack width, and water content, are examined. e crack development-closure characteristics of soil layer are analyzed by the orthogonal test method. e aim of the work is to provide a reference for the stability analysis of overlying soil and the protection of underground latent water resources in thin bedrock geological regions during thin bedrock coal seam mining
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
