Abstract
In the reuse stage of a gob-side entry retaining, failure of the structure and stability of the main roof have a significant effect on the safety of the advanced support and ventilation space at the working face. In this study, field investigation, theoretical analysis, and industrial experimentation were performed to analyse the fracture characteristics and formation process of the gob-side entry retaining roof during the reuse period. A dynamic-equilibrium mechanical model of the main roof structure is presented and the formation mechanisms of different types of short cantilever rock beam structures are clarified. The following major conclusions are drawn: (1) Three types of short cantilever rock beam structures occur in the main roof of a gob-side entry retaining during the reuse period, namely, the “short cantilever-articulated rock beam” structure, “short cantilever step rock beam (type I)” structure, and “short cantilever step rock beam (type II)” structure. (2) The stability criterion for these three short cantilever rock beam structures was also determined; that is, when the sliding instability coefficient K ≥ 1, the short cantilever-articulated rock beam structure will form, and when the sliding instability coefficient K < 1, the short cantilever step rock beam (type I or II) will form. (3) The governing law for the thicknesses of the main roof, immediate roof, and coal seam of the short cantilever rock beam structure was clarified; namely, the K-value gradually increases with increases in the thickness of the coal seam, drops sharply and then decreases gradually with increases in the thickness of the main roof, and decreases slowly with increases in the thickness of the immediate roof. The research results were validated at the gob-side entry retaining project in the Huainan mining area and have theoretical significance and reference value for roadway support projects with similar conditions.
Highlights
With the continuous improvements in coal mining methods and mechanical equipment, gob-side entry retaining has become an important factor in the scientific and technical development of coal mining in China [1, 2]. is technique has been widely applied and has a prominent position in China’s coal industries, including the China Energy Investment Group, Shandong Energy Xinwen Mining Group, China Pingmei Shenma Group, Jizhong Energy Group, and Huainan Mining Group
Numerous achievements have been made in the control theory and support technology of gobside entry retaining in recent years
Han et al [6] conducted a physical simulation experiment to illustrate the characteristics of the collapse of sequential overlying strata in goaf and its superposition disturbance mechanism with respect to gob-side entry retaining
Summary
With the continuous improvements in coal mining methods and mechanical equipment, gob-side entry retaining has become an important factor in the scientific and technical development of coal mining in China [1, 2]. is technique has been widely applied and has a prominent position in China’s coal industries, including the China Energy Investment Group, Shandong Energy Xinwen Mining Group, China Pingmei Shenma Group, Jizhong Energy Group, and Huainan Mining Group. Zhang et al [13] studied the stability of the surrounding rock during reuse of a roadway constructed by roof cutting in a three-soft coal seam and clarified the spatial-temporal evolution law of the stress field and displacement field of the surrounding rock during the reuse period He et al [14,15,16] put forward a creative theory for roof cutting a short wall beam. Few studies have addressed the failure mechanism and stability of the precracked roof structure of a gob-side entry retaining during the reuse period, which requires further exploration. The dynamic failure process and failure mechanism of the main roof in a gob-side entry retaining are investigated and classified at different stages of the mining process, with particular attention given to the formation process of the rock beam of the precracked main roof during the reuse period. Taking the gob-side entry retaining in the Huainan mining area as the engineering background, the research results were validated in industrial experiments
Sign-in/Register to view highlights & summary 
Paper version not known (
Free)
Published Version
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