An Innovative Approach for Gob-Side Entry Retaining With Thick and Hard Roof: A Case Study

Abstract

An innovative roadway layout in a Chinese colliery based on gob-side entry retaining (GER) with thick and hard roof (THR) was introduced. Suspended roof is left with a large area in GER with THR, which leads to large area roof weighting (LARW). LARW for GER with THR and mechanism of shallow-hole blasting to force roof caving in GER were expounded. Key parameters of shallow-hole blasting to force roof caving are proposed. LS-DYNA3D was used to validate the rationality of those key parameters, and UDEC was used to discuss and validate shallow-hole blasting to force roof-caving effect by contrast to the model without blasting and the model with shallow-hole blasting. Moreover, shallow-hole blasting technology to force roof caving for GER with THR was carried out in the Chinese colliery as a case study. Field test indicates that shallow-hole blasting technology effectively controls ground deformation of GER with THR and prevents LARW.

Stability mechanism and countermeasure of the solid coal rib in deep gob-side entry retaining: Insights from theoretical analysis numerical simulation

“…Based on numerous field practices in GER [ 10 , 16 , 17 ], it has been observed that: (i) The impact of the overlying strata beneath the primary key stratum on the main roof (sub-key stratum) is significantly more significant than that of roadway support; (ii) The construction of the filling body along gob side can only occur at a specific distance behind the working face and often faces challenges in achieving complete connection with the immediate roof. Its supportive role becomes effective only when there is a certain degree of roof subsidence, indicating its passive nature.…”

“…Consequently, this will increase stability of the plastic solid coal rib [ 39 , 40 ]. Consider using early strength materials with rapid resistance increasing properties for constructing filling body [ 10 ]. By doing so, load sharing between filling body and solid coal rib can occur at an earlier stage.…”

“…It achieves this by reducing the necessity for extensive roadway excavation, mitigating mining tension, enhancing resource recovery efficiency, eliminating stress concentration on coal pillars, and addressing the issue of gas accumulation in upper corners [ [1] , [2] , [3] , [4] , [5] , [6] ]. Over time, GER technology has been progressively applied across various coal seam thicknesses - from thin seams (less than 1.3 m) [ [7] , [8] , [9] ], medium-thick seams (1.3 m–3.5 m) [ [10] , [11] , [12] ], fully mechanized thick seams (more than 3.5 m) [ [13] , [14] , [15] ], to even fully mechanized top coal caving mining operations [ 16 , 17 ]. Notably, this technology has been successfully employed at depths exceeding 1000 m [ 18 , 19 ].…”

Asymmetric support technology for gob side entry retaining with high water material

“…The gob side entry retaining is the use of special materials in the roadway side to construct a roadway protection belt, the retained roadway to serve the next working face (Zhang et al, 2018;Zhao, 2019). The gob side entry retaining can realize the Y-type ventilation, effectively solve the problem of gas overrun in the upper corner, and realize gas pre-extraction of adjacent coal seams, which provides a guarantee for safe mining (Zhang and Li, 2019).…”

Delineation and Prevention of the Spontaneous Combustion Dangerous Area of Coal in a Regenerated Roof: A Case Study in the Zhoujing Coal Mine, China

“…Coal is the main energy source in China, accounting for more than 60% of the energy consumption structure. − In the past and over a long period of time, coal mining was characterized by high-intensity and extensive mining. In pursuit of production growth, a large number of high-quality coal resources have been abandoned and wasted, including the thin coal seam that is not mined in the process of multi-seam mining, the top coal that is left for roof protection in layered mining, and the top coal and bottom coal left in the process of medium thick coal mining, among others. − Recovery of these coal resources can effectively improve the recovery rate and extend the service life of the mine. However, in the process of remining, the roof rocks that fall after the original coal seam is mined are compacted and cemented to form a regenerated roof .…”