Research on Gob-Side Entry Retaining Mining of Fully Mechanized Working Face in Steeply Inclined Coal Seam: A Case in Xinqiang Coal Mine

Abstract

As a kind of non-coal pillar roadway support technique, gob-side entry retaining is of great significance to improve the production efficiency of a fully mechanized working face. However, the construction of the roadway is often subject to the surrounding rock conditions, the application is mainly concentrated in the nearly horizontal and gently inclined coal seam conditions, and the application in the steeply inclined coal seam conditions is relatively less. This paper is based on the gob-side entry retaining roadway construction of the 58# upper right 3# working face in the fifth district of Xinqiang Coal Mine, and describes the investigation in which we measured the advanced abutment stress, mining stress, and roof stress and analyzed the moving rule of roof. On this basis, in this work, we determined the filling parameters and process and investigated the filling effect from the perspective of the deformation of the filling body and the surrounding rock. The results show that the influence range of the advanced abutment stress in the working face is about 20~25 m, the stress in the upper part is intense, and stress in the middle and lower parts are relaxed. The setting load, the cycle-end resistance, and the time-weighted mean resistance at the upper end of working face along the direction of length are the largest, followed by the middle part, and the lower end is the minimum. When exploiting the steep inclined coal seam, the upper part of the working face is more active than the lower part, and the damaging range of overlaying strata is mainly in the upper part of the goaf. With this research, we established the filling mining process in steeply inclined coal seams and determined the relevant parameters. The gangue cement mortar filling can ensure the deformation of the filling body, the surrounding rock of the roadway is small in the process of roadway retention, and the stress of the filling body is also small, which ensure the successful retention of the roadway. This study verifies the possibility of repair-less exploitation and provides a reference for the popularization and application of the gob-side entry retaining technique in steep inclined coal seam.

Numerical Investigation of the Influence of Roof-Cutting Parameters on the Stability of Top Coal Gob-Side Entry Retaining by Roof Pre-Fracturing in Ultra-Thick Coal Seam

“…With the introduction of mechanized mining equipment and support technology, high-strength support materials such as scalable hydraulic supports, anchors, and cables were used for supporting, and high-water materials and flexible membrane filling bodies were used to replace coal pillars [21][22][23][24]. At the same time, the gob-side entry retaining system suitable for use in China was proposed in combination with the domestic coal seam mining conditions, and its continuous application and development [25][26][27], application trend in the transition from simple geological conditions to complex geological conditions, and the retaining of the gob-side entry using the roof cutting coal pillarless mining technique has achieved certain results in the comprehensive mining of medium-thick coal seams and steep conditions [28][29][30]. This roadway protection method significantly improved the coal recovery rate and solved the problems of mining relay and gas accumulation [31,32], and became the main stream for thick coal seam mining, but the solidification of the filling material and the mining speed need to be accurately coordinated and it is difficult to determine the strength of the surrounding rock in time.…”