Failure mechanism and divisional differentiated control of surrounding rock in mining roadway under remaining coal pillar in close‐distance coal seam

Abstract

Regarding the issue of intense mining pressure appearing in the underlying gateway below the remaining coal pillar in the close‐distance coal seam (the remaining coal pillar is perpendicular to the underlying section coal pillar), 401 working face is used as the engineering background. Field measurements, laboratory experiments, numerical simulations, and engineering verification techniques are used to study the abutment pressure's evolution properties and the plastic zone's propagation laws before and after the underlying coal seam roadway experienced the mining impact. The conclusions are as follows: ① The maximum plastic area on the two sides and the roof of the roadway underlying the gob are up to 2 and 1.5 m, whereas the maximum plastic area on the two sides and the roof of the roadway underlying the remaining coal pillar are up to 5 and 4.5 m, respectively. Moreover, the plastic area extends along the two sides, and the section coal pillar is completely broken when the working face is mined below the remaining coal pillar. ② The stress increase coefficient K in the overlap area of the remaining coal pillar and the underlying section coal pillar reaches 3.4 when the mining face penetrates the underlying remaining coal pillar and the advance abutment pressure is overlaid with the concentrated stress of the coal pillar. ③ When the underlying working face is mined to 4, −2, −8, and −14 m away from the remaining coal pillar, the damage range of the roadway 5–10 m ahead increases in turn. At the same time, the maximum plastic area of the roof passes through the plastic area of the upper coal seam floor. Therefore, the underlying and transition areas on both sides of the remaining coal pillar are divided into Area I (15 m) → Area II (the most complicated area to control under the remaining coal pillar, 20 m) → Area III (25 m) according to the width. Furthermore, the divisional differentiated combined control technology of channel steel truss anchor cable with joint double‐way locking control function of roof and coal pillar in Areas I and III, while channel steel truss anchor cable with joint double‐way locking control function of roof and side + high resistance integral door‐type support is proposed in Area II. Field engineering practice shows that the deformation of the roadway surrounding rock can be controlled within 210 mm after adopting the above divisional combined control technology. Finally, the mining operation can safely and efficiently pass through the remaining coal pillar. The research results have important reference values for surrounding rock control of mining roadways in the overlapping area of similar “+”‐type cross‐working face.

Stress redistribution in a multilayer chamber for compressed air energy storage in abandoned coalmine: Elastic analytical insights and material choice

“…9,13 In terms of technical issues, the stability of gas storage chamber is caused by stress and displacement. 14 Therefore, this paper will explore the issue of chamber stability through the analysis of stress and displacement.…”

“…The success of a CAES lies in successfully addressing the following issues: chamber stability, 11 compressed air leakage, 12 environmental impacts, 9 and some system factors 9,13 . In terms of technical issues, the stability of gas storage chamber is caused by stress and displacement 14 . Therefore, this paper will explore the issue of chamber stability through the analysis of stress and displacement.…”

“…The CAES chamber stability is a critical problem to the construction of CAES chamber with abandoned coalmine roadways. The roadways usually have soft surrounding rocks with excavation‐induced damages, 14 thus a CAES chamber in coal mines has three features: First, the chamber is usually a three‐layer structure with surrounding rock, lining reinforced concrete and grout layer. Second, it is usually subjected to nonhydrostatic external loads.…”

Study on the Upper Limit of Roof Failure in Soft Rock Roadway

“…Jia et al [11,12] used FLAC 3D numerical simulation software to investigate roadway roofs containing coal seams of diferent thicknesses with low strength, identifying the primary causes of severe deformation of soft rock roadways. Li et al [13][14][15][16] determined the distribution pattern of the plastic zone of the surrounding rock of the roadway through theoretical analysis. In response to the failure characteristics of soft rock roadways, Zhao et al [17][18][19][20] examined the deformation mechanism of deep roadways and proposed a composite support technology for the surrounding rock.…”

The J2 evolution model and control technology of the main roadway surrounding rock under superimposed influence of double-coal seam mining

“…The upper seam is mined out, and the stress field distribution in the lower coal face is mainly affected by vertical stress; the next is horizontal stress 23,24 . The superposition of the coal seam stress field is not only affected by the spacing between two coal seams but also closely related to the arrangement of the coal face (can be roughly divided into two types:"+" type and "−"Type) [25][26][27] . Some scholars have studied the behaviors of rock pressure, such as rock bursts, which may be caused by complex stress distribution under the condition of multi-seam mining, the control method which can be applied to engineering practice is put forward [28][29][30][31] .…”