Research On Key Technology Of Roadway Retention Along Goaf Under The Condition Of Inclined Thick Layer And Hard Roof

Sichuan Dazhu Coal and Electricity Group's Bolin Coal Mine-2446(k26)fully mechanized mining face has technical difficulties in retaining roadways along the goaf.Using theoretical analysis,numerical simulation,laboratory tests,on-site monitoring and other methods,the law of overlying strata migration in the stope with sloping thick layers and hard roof is revealed.The control plan of the surrounding rock in the roadway was determined.The key parameters of roof cutting and pressure relief were studied,and a reasonable roadside support was designed.In the end,a key technology system for roadway retention along goafs with inclined thick and hard roof is formed,with the core of roadway support,roof cutting and pressure relief,and roadside support.The main research results of this paper are as follows:(1)Analyzed the law of overlying rock migration in the sloping thick-layer hard roof stope,and put forward the four-stage and four-region surrounding rock control key points for retaining roadways along the goaf.According to the migration law of overlying rock in the stope,the design principle of roadside support body of "concession in the early stage and pressure resistance in the later stage" is determined,and the mechanical structure model of "soft-hard" combined roadside support is established,and the calculation of roadside support resistance is derived.formula.(2)According to the key points of the surrounding rock control of the roadway remaining along the goaf,the principle of the surrounding rock control in the roadway is determined,and the basic support plan in the roadway and the strengthened support plan in the roadway are designed.The theoretical range value of the key parameters of top-cutting and pressure-relief is obtained through theoretical calculation,and then numerical simulation is used to determine the optimal value of the key parameters of top-cutting and pressure-relief.(3)In order to ensure that the side roof of the goaf fully falls,the two-way energy-concentrated tension pre-splitting blasting technology is used to cut the roof of the side roof of the goaf to relieve pressure.Through theoretical calculation and numerical simulation analysis,it is determined that the top cutting height is 5.5 m,the top cutting angle is 10°,and the blasting pre-split hole spacing is 600 mm.(4)The dimensions of the roadside support materials and precast concrete blocks are determined,and the layout of the roadside support and the "L"-shaped retaining wall steel mesh are designed.The influence of three factors of water-cement ratio,steel fiber content and coal gangue particle size on the compressive strength of precast concrete blocks was studied by orthogonal experiment method,and the optimal ratio of precast concrete blocks was obtained.The above-mentioned research results were applied to the fully mechanized mining face of Berlin Coal Mine-2446(k26)and succeeded,ensuring the safe and efficient mining of the fully mechanized mining face.