Mechanism of pressure relief by advanced pre-splitting in gob-side entry retaining and arrangement principle of pre-splitting boreholes
In the hope of clarifying the mechanism of pressure relief by advanced pre-splitting in gob-side entry retaining and elucidating the arrangement principle of pre-splitting boreholes,a numerical model for pressure relief in gob-side entry retaining with concrete columns as roadside support was estab-lished.With this model,the influences of pre-splitting angle and pre-splitting height on the stress in sur-rounding rock of retained roadway and the compression amount on the top surface of columns were ana-lyzed by simulation.The analysis confirmed the pressure relief and subsidence reduction effects of ad-vanced pre-splitting on the retained roadway.On this basis,the pressure relief mechanism of advanced pre-splitting in gob-side entry retaining was revealed,and the arrangement principle of pre-splitting bore-holes was proposed,which were then verified in engineering applications.The results show that advanced pre-splitting has significant pressure relief and subsidence reduction effects on the retained roadway.The pressure relief effect is mainly reflected in alleviating the stress concentration of surround-ing rock around the retained roadway.A pre-splitting zone is artificially created by means of advanced pre-splitting to cut off the thick and hard roof inside the lateral overhanging roof above the retained road-way,thus cutting off transmission paths of the load from the overburden above the goaf and reducing the pressure exerted by the lateral overhanging roof on the retained roadway.As a result,pressure relief is achieved in the retained roadway.Moreover,the pressure relief and subsidence reduction effects are pos-itively correlated with the pre-splitting angle and the pre-splitting height.The inclination angle of pre-splitting boreholes should be as large as possible,and their length is supposed to be large enough,at least higher than the first main roof above the caving zone,to penetrate the thick and hard roof to the full.The 50108 mining face in Hejiata Coal Mine is recovered by gob-side entry retaining with concrete columns as roadside support.The pre-splitting borehole is 80° in inclination angle and 29.0 m in vertical depth,which exceeds the second main roof.The average pressure of end supports is 29％lower than that without pre-splitting,exhibiting a remarkable pressure relief effect.
gob-side entry retainingpre-splitting ahead of longwall facepre-splitting boreholespres-sure reliefnumerical simulation
万方数据
维普
