Study on Overburden Structure Characteristics and Fracture Evolution Law in Upward Mining at Kuangou Coal Mine

DOI: https://doi.org/10.62517/jes.202302303

Author(s)

Xiaoqian Yuchi1,2

Affiliation(s)

1College of Energy Science and Engineering, Xi’an University of Science and Technology, Xi’an, Shaanxi, China 2Key Laboratory of Western Mine Exploitation and Hazard Prevention, Ministry of Education, Xi’an University of Science and Technology, Xi’an, Shaanxi, China

Abstract

The development of vertical fractures in the overburden rock below after upward mining of a coal seam can influence the safe mining of both this seam and the seams above. This paper employs the method of physical similarity simulation to experimentally study the overburden structure and fracture evolution law during upward mining of the No. 4 coal seam in Kuangou Coal Mine. The study reveals that the overburden rock of the lower No. 4 coal seam after mining exhibits a typical "three-zone" characteristic, with the caved zone overburden showing a distinct cantilever beam-hinged structure, and the overburden structure of the bending and sinking zone is relatively intact. In the experiment, no significant vertical through-layer fractures were observed during the first five periodic pressures. However, during the 6th to 11th periodic pressure periods, when mining pressure became intense, a total of six vertical through-layer fractures appeared near the coal wall of the working face. These fractures, aligned with the caving angle direction, extended upwards through the No. 3 coal seam located 60m above the No. 4 seam. The overall fracture evolution showed opening during intense mining pressure and gradual closing after the pressure subsided. Two of these vertical through-layer fractures had a larger extension range, eventually reaching the surface. During the upward mining process, the appearance of vertical through-layer fractures did not lead to sliding instability or rapid sinking of the overburden roof. The working face could thus continuously advance. This research has implications for the safe upward mining in similar mines.

Keywords

Upward Mining; Physical Similarity Simulation; Vertical Through-Layer Fracture; Overburden Structure

References

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