Numerical insights into stress redistribution in protected seam mining with coal pillars and an application to methane control

Abstract

This paper identifies the stress redistribution of protected seams under the influence of coal pillars and a divisional management strategy for methane control. A coal pillar that is reserved in the protective seam greatly affects the abutment stress, the O-shaped circle's evolution and the stress distribution. The strain-soften model was conducted using FLAC3D numerical analysis software to investigate the stress redistribution in the protected seam mining process. The results show that the abutment stress reaches a maximum value of 1.25 times the original stress when a protected seam coal face lies in the center of the coal pillar's affected zone. The O-shaped circle is divided into two parts by the coal pillar, and its developmental width is closely associated with the protected seam mining stage and the developmental height of the "three zones", especially the fractured zone. The stress redistribution of protected seam is rarely affected by the coal pillar when the distance is greater than 26 m. Both the total increased stress belt of the coal pillar affected zone and the total decreased stress belt of the other zones along the vertical direction significantly influence the methane migration. We propose a divisional management strategy that supplies a theoretical basis and technical guidance for methane control.

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

“…[42][43][44] In addition, a high-strength concrete spray layer can seal the shallow surrounding rock to effectively limit the arbitrary expansion of the surrounding rock fracture zone, thereby maintaining the integrity of the surrounding rock. [45][46][47][48][49][50][51][52][53][54][55][56][57] It can be seen that the coupled actions of the high-strength pretensioned anchor bolts and anchor cables with surface protecting components such as the plate and steel mesh, along with the high-strength concrete spray layer, constitute the high-strength "anchorage-mesh-shotcrete" support system for the goaf roof, as shown in Figure 5…”

“…However, the combined support of the high‐strength pretensioned anchor bolts and anchor cables can place the surrounding rock in a compression state and effectively control the deformation and failure of the surrounding rock in deep and shallow anchorage zones 42‐44 . In addition, a high‐strength concrete spray layer can seal the shallow surrounding rock to effectively limit the arbitrary expansion of the surrounding rock fracture zone, thereby maintaining the integrity of the surrounding rock 45‐57 . It can be seen that the coupled actions of the high‐strength pretensioned anchor bolts and anchor cables with surface protecting components such as the plate and steel mesh, along with the high‐strength concrete spray layer, constitute the high‐strength “anchorage‐mesh‐shotcrete” support system for the goaf roof, as shown in Figure 5.…”

Heat–fluid–solid-coupled model of flue gas displacement CH 4 in coal seams and application

“…Zhang [11] , Wang [12] , and Yang [13] found that the gas flooding technology for CH4 extraction is more feasible in principle and effect than single-gas injection through a field application of single-gas injection to displace coal seam gas. Jia [14] , He [15] , and Fan [16] concluded that N2-ECBM and CO2-ECBM can significantly improve the CH4 extraction rate through a numerical simulation of single-gas flooding of a CH4-containing coal seam. Some scholars have experimentally studied the injection of a mixture of gases, such as N2 and CO2, into coal seams to improve the gas extraction efficiency.…”

Ground Response of Non-Coal Pillar Mining Panel

“…Underground coal seam extraction causes a disturbance and redistribution of the in situ stress field [1][2][3]. Hence, the mining-induced ground response (MIGR), including roof caving, surrounding rock fracturing, and ground subsidence, may occur around the extracted area.…”