Study On Mechanism Of Bolt-mesh-cable Support Release And Application Of Mining Roadway

Bolt-mesh-cable support has an important role on ensuring the stability of tunnel surrounding rock, simplifying end processes of mining face, etc. However, due to combination of bolt-mesh-cable supporting role, cut hole and end backside roof can not timely collapse with the mining face advance, causing a large range of hanging roof of cut hole and end backside, resulting in a series of safety problems. First of all, the large range of hanging roof on mining face end backside form ventilation dead angle and leak air to mined-out area and other serious safety problems; Secondly, larger bearing pressure of coal pillar near cut hole and both sides of mined-out area is formed, which weakens of coal pillars stability and affect the stability of adjacent roadway surrounding rock, makes adjacent roadway maintenance problems. With comprehensive use of theoretical analysis, numerical simulation and site observation, the systematic study of the mechanism and methods of bolt-mesh-cable release was performed, the main research achievements are as follows:(1) Surrounding rock reinforcement mechanism of bolt-mesh-cable support was explored, the roof rock patterns before and after bolt-mesh-cable release as well as impact on ventilation safety were studied, failure mechanism of composite beam and suspension role and characteristics of curved triangular block stability of bolt-mesh-cable was theoretically analyzed, bolt-mesh-cable release impact laws to mined-out area both side hanging roof timely collapse has been gained.(2) Winkler elastic foundation beam model for bolt-mesh-cable release impact analysis to coal pillar bearing pressure is established, the bolt-mesh-cable release impact to coal pillar bearing pressure and changing characteristics of coal pillar yield zone are analyzed, laws of coal pillar bearing pressure change with hanging roof length as well as coal pillar yield zone size change with coal pillar strength and hanging roof length are obtained.(3) By means of numerical simulation method, bolt-mesh-cable release impact to coal pillar and adjacent roadway surrounding rock stability is analyzed, studies shows that: coal pillar bearing pressure and yield zone size decreases with the length of hanging roof decreases, coal pillar stability is strengthened with bolt-mesh-cable release; adjacent roadway roof sinking amount, two side displacement and floor heave significantly decreased with the hanging roof length reduced, roadway surrounding rock stability is improved with bolt-mesh-cable release. (4) Based on analysis of bolting mechanism, considering the requirements of later stage bolt release, a new type of resin retrievable bolt structure was developed and designed, and underground tests was carried out. The results shows that: the new retrievable bolt has a good ability to adapt soft rock and coal seam roadway, and is convenient to install and recycling, provides a guarantee for bolt release technology application.(5)Cut hole and roadway bolt-mesh-cable release technology was initially developed, and applied to coal mining practices. The field observation experiments show that the roof can timely collapse, mining face roof management and mined-out area air leakage and other safety problems are effectively solved, adjacent roadway surrounding rock stress concentration has been markedly alleviated, roadway surrounding rock deformation has been effectively controlled, and achieved remarkable economic and social benefits.