Study On Surrounding Rocks Stabilization Mechanism And Application For Gob-Side Entry Retaining Without Backfilling Wall Of The Shallow-Buried And First Thin Coalface

In order to solve the high tension of coal working face, and improve resource extraction rate, continuous mining technology of pillarless gob-side entry retaining was adopted for No. 2 coal seam in Laomupo coal mine. At first, the breaking law of lateral rocks was analyzed, and then the relationship between the lateral rocks breaking law and abutment pressure distribution characteristics was analyzed,which contributed to optimize and design the puissant and cutting supports for supporting roadway-side and deduce the proper formulas of supporting parameters in different mining conditions. Main results as follow.(1) breaking forms of roof lateral rock in gob-side entry retaining are rotation subside and sink vertically. the main breaking form in the early stage is rotation subside and the pressure towards roadway comes from immediate roof. secondary crushing from roof lateral rocks is the main breaking form in the transition period.Outer layer forms a self-stabilization structure. The later activity of lateral roof rocks is primarily sinking vertically and inner layer formed in this period bears weight from caving zone.(2) The study on the breaking law of lateral roof rocks in gob-side entry retaining was simplified to the breaking of boards, using plate yield line analysis principles to speculate calculations of lateral breaking parameters in both first pressure and periodic weighting, on the basis of which, the breaking position of lateral roof rocks was conformed, the breaking law on both sides of the working face was disclosed and the distribution of abutment pressure was divided. H>[H]or σo<(σo)min is the judgment standard of existence condition for internal stress field.(3) Analyzing the key technology of pillarless gob-side entry retaining,anchor-wire-rope combined supporting method was applied to roadway-in entry retaining, and supports were designed to use in roadway-side which have numerous mechanical properties, including puissant roof rock breaking, high resistance,initiative to support and certain shrinkable, adapting the sinking of roof rocks. In addition, the special sollerets were used to control the stability of bottom slab.(4) By numerical simulation, compared the offshoot stress and deformation of support structure used in roadway-side entry retaining in the protecting entry techniques of pillarless and coal pillar gob-side entry retaining, explaining the feasibility of pillarless gob-side entry retaining. The results show that using thetechnology of pillarless gob-side entry retaining is able to maintain the stability of surrounding rocks in the given coal seam.(5) Supporting parameters were checked. Roof-cut resistance of lateral roof is1000 k N, which is reasonable. Nominal yield of support is greater than 201mm;support strength in roadway should be designed to at least 197KN; support base area should be 1500cm2. Roadway deformation is within reasonable limits, so the application about the technology of pillarless gob-side entry retaining described in this paper is reasonable under relatively simple geological conditions, such as a shallow and no gas outburst coal mine.The success to use pillarless gob-side entry retaining technology is a good way to enhance economic efficiency in a simple geological condition. The technology and site management experience accumulated in practices are of high value to a certain extent.