Abstract
This study presents an integrated approach including the theoretical analysis and numerical modelling to investigate the failure characteristics of the overlying strata in the shallow-buried stope. The mechanical characteristics of the caving zone are first revealed and then calibrated by using the double-yield model. The theoretical results show that the mechanical properties of the collapsed rock mass are closely related to its crushing expansion coefficient and uniaxial compressive strength. The vertical stress of the collapsed rock mass increases slowly with the strain and then increases exponentially after a certain critical strain. The simulation indicates that the fracture zone volume is 1.7-1.8 times that of the caving zone in the 31108 working face, and the failure volume of the overlying strata is 9-10 times that of the stope. The simulated height of the caving zone and fracture zone is 9 m and 20 m, respectively. The comparison between the numerical and field measurement results demonstrates that the new evaluation method using shear-tensile strain behaviors can accurately predicate the height of the two zones. The proposed numerical method could be a viable alternative approach to two zones height calculation.
Highlights
Western China is rich in coal resources, accounting for 65% of the country’s total reserves, but water resources reserves only account for 3.9% [1, 2]. e lack of water resources seriously limits the sustainable development of energy in Western China
Water storage in goaf formed after coal mining has become an important technical way to handle the contradiction between coal mining and water resources protection in Western China
In the process of coal mining, the caving zone, fracture zone, and bending subsidence zone are formed from bottom to top with the movement of the overlying strata [4,5,6]. e water storage capacity of the underground reservoir is directly determined by the failure mode and height of the caving zone and fracture zone [7]. erefore, it is urgent to understand the failure mode and height of the overlying strata during coal seam mining
Summary
Western China is rich in coal resources, accounting for 65% of the country’s total reserves, but water resources reserves only account for 3.9% [1, 2]. e lack of water resources seriously limits the sustainable development of energy in Western China. Theoretical analysis, field measurement, and numerical modelling are the most used method to predict the development height of the water flowing fractured zone. Erefore, it is urgent to conduct numerical research on the movement laws of overlying strata considering the compaction effect of goaf. A numerical method by using FLAC3D is presented to investigate the range of caving and fracture zones by discerning the plastic strain value of the zones in the model. In this modelling method, the compaction effect of the goaf is achieved by using the double-yield constitution model.
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