Abstract
The roadway of S2S2 fully mechanized caving face (FMCF) in Xiaokang Coal Mine is one of the most typical deep-buried soft-rock roadways in China and had been repaired several times. In order to figure out the failure reasons of the original roadway support, the geological conditions were investigated, the surrounding rock stress was monitored, the rib displacement, roof separation, and floor heave were in situ measured, and the performance of the U-shaped steel support was simulated. The above analysis results indicated that the support failure was mainly caused by (1) the unreasonable arch roadway section, (2) the high and complex surrounding rock stress, (3) the failure control of the floor heave, and (4) the inadequate self-supporting capacity of the surrounding rock. For optimizing, the roadway section was changed to circle and a new full-section combined support system of “belt-cable-mesh-shotcrete and U-shaped steel-filling behind the support” was adopted, which could specifically control the floor heave, allow the roadway deformation in control, and improve the self-supporting ability and stress field of the surrounding rock. To determine the support parameters, the selected U-shaped steel support was verified by simulation, and various bolt-cable support schemes were simulated and compared. Finally, such an optimized support scheme was applied in the roadway of the next replacement FMCF. The in situ monitoring showed that the rib-to-rib convergence and roof-to-floor convergence were both controlled within 600 mm, which indicated that the roadway was effectively controlled. This case study has important reference value and guiding function for the optimal design of the soft-rock roadway support with similar geological conditions.
Highlights
As coal mining depth increases, the roadway support is generally faced with the difficult problems caused by soft rock and high ground stress [1,2,3]
The new proposed support scheme was carried out in the roadway of the replacement fully mechanized caving face (FMCF), and the in situ monitoring was carried out to identify the effect of the new support system
It was the overload pressure that caused the failure of the U-shaped steel support. e in situ measurement and simulation results indicated that it was the unreasonable roadway section and the failure control of the floor heave that weakened the self-supporting capacity of the surrounding rock, caused the complex surrounding rock stress, and resulted in the failure of the initial soft-rock roadway support
Summary
As coal mining depth increases, the roadway support is generally faced with the difficult problems caused by soft rock and high ground stress [1,2,3]. E research on the theory and technology of the softrock roadway support under high ground stress is active, and a series of research results have been obtained He et al [13] proposed the coupling support concept of roadway and developed the technical system of active support; Kang and Wang [14] put forward the theory of high pretensioned stress and intensive bolting system and developed a complete technology of bolt support for coal mine; Gao et al [15] developed the concrete-filled steel tube support technology; Jiang et al [16] analyzed the mechanism of different types of roadway floor heaves and proposed corresponding prevention and control measures. The new proposed support scheme was carried out in the roadway of the replacement FMCF, and the in situ monitoring was carried out to identify the effect of the new support system
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