Research on the Reasonable Width of the Waterproof Coal Pillar during the Mining of a Shallow Coal Seam Located Close to a Reservoir

Abstract

Retaining a waterproof coal pillar is the most effective water conservation method for coal seam mining close to a reservoir, and determining a reasonable width for the waterproof coal pillar has been a common problem among mining scholars for a considerably long time. In case of mining a 4−2 coal seam close to the Changjiagou Reservoir in the Zhangjiamao mine, the research methods of theoretical analysis, physical simulation using similar materials, and numerical simulation have been adopted to analyze the overburden strata mining failure features and the surface subsidence law. Additionally, the influences of the width of the coal pillar on the reservoir bank slope stability have been investigated. The results denote that a coal pillar can be divided into a mine-pressure-influenced zone, an effective waterproof zone, and a water-level-influenced zone with respect to water resistance. Furthermore, the width of the waterproof coal pillar was determined to be 107.41 m by theoretical analysis. The simulation test indicated that when the working face advanced close to the reservoir, the reservoir bank exhibited vertical downward as well as transverse abscission layer fractures and the divided topsoil slipped toward the reservoir. Subsequently, the judgment conditions required for determining the critical width of the waterproof coal pillar were proposed based on the requirements to prevent the reservoir bank slope from instability failure and the water gushing accident in goaf. The maximum width of the waterproof coal pillar when the top point on the slope surface experienced reverse horizontal displacement and several key points produced sharp vertical displacements or when the pore pressure in the coal seam roof and floor suddenly became 0 was considered to be the critical width. Furthermore, the critical width was determined to be 96 m via simulation analysis, verifying the rationality of the theoretical method. These results could provide a theoretical basis for determining the width of the waterproof coal pillar of the coal seam located close to a reservoir.

Width Design of Small Coal Pillar of Gob‐Side Entry Driving in Soft Rock Working Face and Its Application of Zaoquan Coal Mine

“…With the continuous improvement of coal mining methods and the enhancement of the mechanical equipment level, fully mechanised caving has become an important mining method for thick coal seam [1][2][3]. It can achieve high-yield and high-efficiency mining of thick coal seams, but roadways in mining area face challenges of surrounding rock control, for example, the large cross section, strong mining influence, and soft and thick coal roof and floor [4][5][6][7].…”

Permeability of Sand-Based Cemented Backfill under Different Stress Conditions: Effects of Confining and Axial Pressures

“…Coal resources threatened by water account for over 27% of the total proven coal reserves. Waterproof coal pillars of large scale need to be left to mine these coal resources using the conventional methods [4,5]. This implies considerable losses of the coal resources and, more importantly, the hidden danger of water burst of coal and rock masses and damage to the aquifer [6][7][8].…”

Structure Partition and Reasonable Width Determination of Waterproof Coal Pillar in Strip Mining

“…When the water conducting fractures connect with a water body, such as water in goaf, the water would flow into the roadway, resulting in water inrush accidents at mines [15][16][17]. Currently, retaining a waterproof coal pillar is considered to be the most effective method for strip mining [18]. Therefore, a reasonable design of a waterproof coal pillar has long been an important research topic in China [19,20].…”

“…The third type includes several theoretical methods. Scholars have researched the determination of the width of the waterproof coal pillar in the cases of coal seam mining under an aquifer and adjacent to water-conducting fault and that of the section coal pillar, which are listed in Table 1 [18]. In these research studies, the failure characteristics of the surrounding rocks that can be attributed to coal seam mining were considered; furthermore, the mine-pressureinfluenced plastic zone and effective waterproof elastic core zone were established on the side of a coal pillar near the roadway, and the failure range caused by high water pressure in deep-buried strata or fault was considered on the side of the influence sources [36][37][38][39].…”