A New Gob-Side Entry Layout Method for Two-Entry Longwall Systems

Abstract

Abstract:The gob-side entry layout is popular at two-entry longwall mine sites in China for the benefit of improving the coal recovery rate. Currently, two methods have been widely used to develop gob-side entries, including gob-side entry retaining and gob-side entry driving. Gob-side entry retaining maximizes the recovery rate by pillarless mining but increases the difficulty in gob-side entry support. Also, this method has limited applications in hard roof conditions. The gob-side entry driving mine site uses the rib pillar to separate the gob entry and the gob area of the previous panel, which leads to additional coal losses. The waste is more intolerable in large-cutting-height panels and longwall top coal caving panels as the Chinese government limits the minimum recovery rate of longwall panels using these mining methods. In this paper, a new gob-side entry layout method, termed gob-side pre-backfill driving, is established to overcome the shortcomings of the existing methods. The new method eliminates rib pillar losses and enhances gob-side entry stability. The feasibility of gob-side pre-backfill driving is studied by numerical modelling and a field trial at Changcun Mine in China. The results indicate that gob-side pre-backfill driving is an alternative for gob-side entry development. This method is practical and also has the potential to bring significant economic benefits to the mining industry.

Combined support technology for main roadway passing through goaf: A case study

“…4. Multiple superpositions of surrounding rock stress fields with complex distributions (Figure 2A): Because of the mining of the original Shiyanhe coal mine, the area of the auxiliary shaft station is in a stress concentration zone of coal pillars with two sides of goafs, [38][39][40][41] superpositioned stress fields in this region, thereby aggravating the control difficulties regarding the main roadway passing through the goaf.…”

“…In addition, the free surface of the roof is increasing, and it is in a fragile equilibrium state, which can easily lead to the failure and instability of the surrounding rock. Large goaf section (Figure 2C): The maximum width of the goaf is more than 15 m. Under the action of roof pressure, the shallow surrounding rock appears to show an evident tensile failure, whereas the deep surrounding rock appears to show a serious shear failure. Furthermore, the maximum sectional area of the goaf is 135 m 2 , and stress concentration in the surrounding rock leads to a large reduction in the strength and bearing capacity of the surrounding rock. Multiple superpositions of surrounding rock stress fields with complex distributions (Figure 2A): Because of the mining of the original Shiyanhe coal mine, the area of the auxiliary shaft station is in a stress concentration zone of coal pillars with two sides of goafs, 38‐41 and the distributions of the goafs and abandoned roadways are unclear. This generates extremely complex, unknown, and multiply superpositioned stress fields in this region, thereby aggravating the control difficulties regarding the main roadway passing through the goaf.…”

Mechanisms of Floor Heave in Roadways Adjacent to a Goaf Caused by the Fracturing of a Competent Roof and Controlling Technology

“…e rock mass is defined as a large structure, and the rock bolts and anchored rock mass are defined as small structures. Studying and understanding the stability of a large number of narrow coal pillars along the tailgate are a prerequisite for large-scale overburden stabilization [13][14][15][16][17][18]. Ground control in tailgates driven along a goaf largely depends on maintaining the stability of the small structure as the large structure breaks and becomes unstable.…”

Gob‐Side Entry Retaining Technology with Advanced Empty Hole Butterfly‐Shaped Weakening in Three‐Soft Coal Seam in China

“…Efficient mining practices are becoming increasingly important as global coal market competition rises. Emerging mining techniques that do not require coal pillar are of great significance for improving resource recovery, reducing roadway heading and mining costs, and enhancing mine production safety [1][2][3][4]. Promoting mining techniques without coal pillar is therefore vital for the technical transformation of production mines, the alleviation of mining relations, and mine life extension.…”