Surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms at the end of mining stage

Abstract

Two case studies were conducted in the Shennan mining area of Shaanxi Province, China to evaluate the surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms. These studies mainly monitored the surrounding rock deformation and coal pillar stress in the recovery rooms of the N1206 panel of 2-2 coal seam at Ningtiaota Coal Mine and the 15205 panel of 5-2 coal seam at Hongliulin Coal Mine. The monitoring results showed that the surrounding rock deformation of the main recovery room and the coal pillar stress in the N1206 and 15205 panels began to increase significantly when the face was 36 m and 42 m away from the terminal line, respectively. After the face entered the main recovery room, the maximum roof-to-floor convergence in the N1206 and 15205 panels was 348.03 mm and 771.24 mm, respectively, and the coal pillar stresses increased more than 5 MPa and 7 MPa, respectively. In addition, analysis of the periodic weighting data showed that the main roof break position of the N1206 and 15205 panels after the longwall face entered the main recovery room was-3.8 m and-8.2 m, respectively. This research shows that when the main roof breaks above the coal pillar, the surrounding rock deformation of the main recovery room and the coal pillar stress increase sharply. The last weighting is the key factor affecting the stability of the main recovery room and the coal pillar; main roof breaks at disadvantageous positions are the main cause of the support crushing accidents.

Dip Angle Effect on the Main Roof First Fracture and Instability in a Fully-mechanized Workface of Steeply Dipping Coal Seams

“…Under the overburden stress, the hinge area of the rock block is bearing compressive force and is likely to experience plastic failure, thus accelerating the rotatory instability of the hinged structure (Wang et al 2019;Sun et al 2019). The rotatory instability model of fractured rock block is shown in Fig.…”

Experimental and numerical study of coal-rock bimaterial composite bodies under triaxial compression

“…The number and severity of mine disasters such as roof fall, floor heave, coal-gas outburst, and rockburst severely grow as the mining depth increases (Li et al 2017Lian et al 2020;Lu et al 2019;Wang et al 2019;Wu et al 2020;Xue et al 2020;Zuo et al 2019Zuo et al , 2020aZhao et al 2018). To reveal the mechanisms of such disasters, many investigations were conducted to test the mechanical behavior of individual rock samples (Dou et al 2020;Guo et al 2019;Yuan et al 2018;Zhao et al 2019;Wang et al 2020;Shen et al 2020) or coal samples (Kim et al 2020;Nikolenko et al 2020).…”

Breaking and mining-induced stress evolution of overlying strata in the working face of a steeply dipping coal seam

“…Producing high-quality coking coal and anthracite yields considerable economic gains (Tu et al 2015;Wu et al 2020). In China, over half of the production of these rare types of coal occurs in steeply dipping coal seams (SDCSs), which make up about 20% of the proven resources (Yun et al 2017;Wang et al 2019Wang et al , 2020. However, SDCS mining safety and efficiency are jeopardized by difficult geological structures and prevailing conditions, the complicated and coupled effects of which require further in-depth investigations (Kulakov 1995;Peng 2006;Wu et al 2014;Das et al 2017;Zuo et al 2020).…”