Thickness and Strength Analysis of Prestressed Anchor (Cable) Compression Arch Based on Safe Co-Mining of Deep Coal and Gas

Abstract

The stability of the gas extraction roadway is very important for the safe mining of coal and gas. The compression arch formed by the combined action of the prestressed bolt (cable) support and surrounding rock has been widely used in the engineering practice of the gas extraction roadway. It is of great engineering application value to analyze the influence of prestressed bolt (cable) parameters on the compression arch. In this paper, combined with the engineering practice of the deep roadway in Huainan and Huaibei mining area of Anhui Province, the mechanical parameters of surrounding rock are measured via field coring and the laboratory. The numerical simulation software FLAC3D is used to analyze the typical position of fractured mudstone, mudstone, sandy mudstone and muddy sandstone under the bolt pre-tightening force of F = 50 kN, 70 kN and 100 kN; the bolt spacing of a × b = 400 mm × 400 mm, 500 mm × 500 mm and 600 mm × 600 mm; the bolt length of L = 1500 mm, 2000 mm, 2600 mm and 3000 mm; and the distribution characteristics of additional compressive stress on the surface of the side. The influence of the different lithology and bolt parameters on the thickness and strength of the compression arch was analyzed, and on this basis, prestressed anchor cables with a pre-tightening force of F = 80 kN, 100 kN and 120 kN and length of L = 3000 mm, 4000 mm and 6000 mm were applied, and their influence on the thickness and strength of the compression arch was analyzed. The results show that the bolt pre-tightening force (F) and the bolt length (L) have a significant effect on the thickness of the compression arch, while the surrounding rock lithology, the bolt spacing (a × b), the anchor cable pre-tightening force (F) and the anchor cable length (L) have no obvious effect on the thickness of the compression arch. The surrounding rock lithology, the bolt pre-tightening force (F), the bolt length (L), the bolt spacing (a × b), the anchor cable pre-tightening force (F) and the anchor cable length (L) have a significant effect on the strength of the compression arch.

Analysis of the Support Failure Mechanism Caused by Bolt Pre-Tightening Force Loss

“…Additionally, the "axial-pressure fastening" effect, induced by bolt pre-tightening, effectively restrains the expansion and slippage of fractured surfaces [11][12][13]. Nevertheless, an excessively high pre-tightening force may promote fracture development within the anchorage body, diminishing its load-bearing and deformation resistance capabilities [14,15]. In essence, maintaining an optimal level of the pre-tightening force is imperative to avert roadway collapses.…”