Mechanical analysis of a vertical-wall, semicircular-arch roadway and a repair technique using double-shell support

Abstract

Roadways in coal mines normally have two vertical side walls and a semicircular arch-shaped roof when viewed in cross section, a design conducive to the stability of surrounding rocks. The North 1 main roadway in Duerping Coal Mine has suffered severe damage and the conventional support method employed there is incapable of ensuring long-term stability of the surrounding rocks. This study provides a mechanical analysis of this vertical-wall, semicircular-arch (VWSA) roadway using a mechanical model. Formulas describing stresses in the rocks surrounding a VWSA roadway were derived through complex analysis. The stress distribution in the surrounding rocks was then predicted using the formulas. Based on the results, a double-shell support structure consisting of an internal shell, a flexible interlayer, and an external shell was developed as a new technique to stabilize surrounding rocks. The functional mechanisms of the three parts and the specific construction procedure are detailed in this paper. Moreover, the key technical parameters were optimized through a comparative analysis of the surrounding rock’s deformation behavior for different shell and interlayer thicknesses. After implementation of this technique, the floor heave, relative displacement between two sides, and roof lowering in the North 1 main roadway decreased to 82, 185, and 161 mm, respectively, which meet the requirements for long-term service. This verifies the effectiveness of the proposed technique in surrounding rock control.