Study On Stability Mechanism Of Rockmass Structure Movement And Its Control In Gob-side Entry Retaining

Based on the analysis of predecessors’ achievements and by comprehensive using oftheoretical analysis, numerical simulation and the method of industrial test, thisdissertation began with overlying strata movement for gob-side entry retaining, establishedthe mechanic model of the structural stability of overlying strata for gob-side entryretaining, analyzed the stability of immediate roof and solid coal rib of the roadway, andrevealed the stability mechanisms of surrounding rock for gob-side entry retaining. On thebasis of getting the rule of surrounding rock movement and rock deformation failure, thelarge deformations control technology of surrounding rock for gob-side entry retaining wasput forward, and stabilization mechanism and control technology of surrounding rock hasbeen preliminarily formed for gob-side entry retaining. Main results are as follows:(1) Based on analysis of the rupture rule of main roof and the load-bearingcharacteristics of roadside packing body, the view of the main roof for gob-side entryretaining secondary breakage, first broke above the solid coal and broke again outside ofpacking body was put forward. The formation mechanism and movement characteristics ofthe main roof secondary breakage were analyzed in detail, which provided the forcefulfoundation for the determination of the control technology of surrounding rock forgob-side entry retaining.(2) The movement characteristics of overlying strata for gob-side entry retainingshowed three clear stages, surrounding rock deformation of gob-side entry retaining wasdivided into three stages, namely, the first mining influence stage, the stable stage ofgob-side entry retaining and the advance influence stage of secondary recovery. Byestablishing the mechanics model of main roof surrounding rock structure for gob-sideentry retaining, the calculation formula of the minimum support strength beside gob-sideentry retaining under three stages were calculated, and the results showed that the firstmining influence stage is the most difficult stage in gob-side entry retaining.(3) It built mechanic models of immediate roof subsidence and solid coal rib of theroadway, respectively, under the condition of main roof of confined deformation, obtainedthe calculation formula of immediate roof and the minimum support strength of solid coalrib of the roadway. Individual analysis the relation of stability of immediate roof and solidcoal rib of the roadway and roadway-in supporting resistance, roadside supportingresistance, solid coal supporting resistance, coal mass strength, bolt length, working face height, etc. Meanwhile, its main influencing factors were obtained, which provides thebasis for road-in support determination of gob-side entry retaining.(4)By analyzing stress and deformation of surrounding rock and distribution law ofplastic zone, the large deformation mechanism of surrounding rock for gob-side entryretaining was obtained. shallow surrounding rock along the unloading direction showsstrong dilatancy deformation and deep surrounding rock shows ductility volume expansionwhile peak stress constantly transfer to the deep of the roadway, its essence of surroundingrock failure is the surrounding rock of gob-side entry retaining by repeatedly loading andunloading effect, cause the principal stress difference increasing. The primary causes oflarge deformation of the gob-side entry retaining are the fracture of the main roof, therotating of the key block and its sinking and slippage. The key to control surrounding rockstability involves improving the integrity of roadway surrounding rock and load-bearingcapacity and preventing crack propagation, which is adapt to the large deformation ofsurrounding rock. The roof above the roadside packing is the key to control parts. Basedon the above, the control requirements and control technology of surrounding rock forgob-side entry retaining was proposed.(5)This dissertation analyzed the stress characteristics and deformation features ofroadside packing body under three stages, obtained the mechanism of roadside packingbody, and study on reasonable supporting parameters of roadside packing with high-watermaterials. According to the deformation feature of packing body to two ribs, prestressingload-bearing frame of packing body was developed, which improved bearing capacity andanti-distortion capacity of packing body with high-water materials massively, and this canfurther reduce packing body width.The above results were applied successfully in two field tests of the Qinxin coal mineand the Jiulishan coal mine under two typical geological conditions of working faces.