Study on the Mechanism of Surrounding Rock Deformation and Its Control for Roof Cutting Retained Gob-Side Entry in Close-Distance Coal Seams Co-Mining

Abstract

Sustainable development in coal mining requires a continuous and efficient method of coal extraction. Research shows that gob-side entries retained through roof cutting retained gob-side (RCGE) are vital for improving mining efficiency, enhancing coal recovery rates, and enabling continuous production. However, the mechanism of surrounding rock deformation during close-distance co-mining of coal seams with this technique is not yet clear. For the Jiaokou coal mine in China, due to an unreasonable stagger distance between upper and lower working faces, the gob-side entries retained at the 9102 tailgate and 10102 headgate experience severe rock pressure, leading to significant prop damage and a sharp reduction in the cross-section of the entry. This greatly hampers the reuse of these entries. To investigate this issue, we established a model to study the stress distribution of surrounding rocks at different stagger distances (20 m, 40 m, 60 m, 80 m, and 120 m) through numerical simulation and optimized the support parameters for the retained entries. Our research found that when the subsidence of the roof in the upper coal seam exceeds 0.74 m but is less than 1.33 m, there is sliding instability in the mining body. When the subsidence exceeds 1.33 m, the mining body will rotate and deform, causing significant mining pressure within the retained entry. A stagger distance of 40 m between the upper and lower working faces can reduce pressure on the face during the mining of the lower coal seam. Extensive field measurements of rock pressure revealed that the damage rate of the single column in the gob-side entries of the upper and lower coal seams does not exceed 5% and 1%, respectively. In summary, this study provides a practical method to reduce damage to entries during the mining process, thereby increasing the continuous production capability of the coal mine. This is critical for the sustainable development of coal mining.

Non-uniform failure and differential pressure relief technology of roadway under irregular goafs in deep close-distance coal seams

“…Wang et al 14 , 15 analyzed the spatiotemporal distribution and dynamic migration laws of toxic gases in the goaf behind the panel during the mining process of close-distance coal seams, and formulated corresponding preventive measures. Zhang et al 16 , 17 elucidated the characteristics of the impact of residual coal pillar in close-distance coal seams on mine pressure, obtained the failure depth and mechanism in goaf floor, and revealed the evolution laws of stress before and after pressure relief in panel of close-distance coal seams. Lu and Ni 18 constructed a mechanical model of roadway floor rock in close-distance coal seams, and obtained reasonable support parameters, grouting material ratio, and grouting pressure for roadway surrounding rock.…”

Mining Technologies Innovative Development II: The Overview

“…Y. Yang, X. Xu, C. Wang in their article, devoted to forming an approach to the study of host rocks deformation in the development of coal seams [14], note that the mechanism of rocks deformation during the close mining of coal seams in coal mines is not sufficiently reflected in the studies. Therefore, the authors proposed a model for studying the distribution of stresses at different distances between deformation zones.…”