Abstract
An overlying rock structure plays a key role in controlling the roof deformation of nonpillar gob-side entry retaining by roof cutting. On the bases of the actual geological conditions of II 632 Haulage Roadway at the Hengyuan coal mine, a similar three-dimensional simulation experiment of roof precutting is conducted. Thereafter, the caving characteristics and migration law of the roof strata in the strike and dip directions are obtained. Moreover, the roof of the retained roadway and key strata of the goaf can form a hinge structure of the key blocks. By monitoring the deformation of the surrounding rock and stress distribution of the roof, the skew deformation characteristics of roadway roof are obtained. By observing the borehole peeping technology, the roof subsidence near the goaf is determined to be greater than that of the solid coal side, and the roof subsidence of the gob-side entry retained by roof cutting is greater than that of the floor heave and two sides approaching. Results of the three-dimensional similar simulation experiment indicate that the mechanical structure model of the key block of the retained roadway roof is constructed, and the mechanical analytical solution of the required support resistance of the retained roadway roof is obtained. This study proposes the constant resistance and large deformation anchor cable reinforcement support method to control the roof deformation of the retaining roadway. Through engineering application, the maximum value of the roof and floor movement of the retained roadway is stable at approximately 650 mm. The retained roadway can meet the demand of the next mining face.
Highlights
Nonpillar gob-side entry retaining by roof cutting mining is one of the key technologies for safe and efficient coal production in China. e application of this technology can effectively improve the recovery rate of coal resources and alleviate the shortage of coal resources [1,2,3,4]
Overburden movement has a substantial effect on the roof of roadway; the disturbance range of the overburden breaking and falling is large, thereby resulting in considerable roof deformation in the process of retaining roadway [5,6,7]
Su et al [9] studied the mechanism of roof cutting and pressure relief in the gob-side roadway (GR) in deep coal mine, and the overburden structure and migration law of GR in deep coal mine have been studied
Summary
Nonpillar gob-side entry retaining by roof cutting mining is one of the key technologies for safe and efficient coal production in China. e application of this technology can effectively improve the recovery rate of coal resources and alleviate the shortage of coal resources [1,2,3,4]. Zhang et al [11] analyzed the disturbance factors during the period of “mining-retaining-using,” through numerical simulation and on-site measurement; the stress and deformation characteristics of the surrounding rock during the reuse of the self-formed roadway were analyzed comprehensively He et al [12,13,14] used the mechanism of roof presplitting and pressure releasing at the goaf side as basis to establish the mechanical model of “surrounding rock structure-roadway side support body” under different roof positions. Sun et al [25] determined that the key parameters affecting gob-side entry retaining in thin coal seam are presplitting cutting height, presplitting cutting angle, and the distance between presplitting blasting holes by analyzing the roof stress state in the process of thin coal seam mining. The research results can provide a theoretical basis and reference value for the roof stability control of gob-side entry retaining by roof cutting
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