| In order to keep the stability of entry and isolate the gob in case of harmful gas overflow and spontaneous combustion of coal seam, Tashan Coal Mine protects the entry by using wide pillar, whose width is 38~45m. Thus results in some problmes, such as heavy loss of coal pillar,heavy strata behaviors, and so on. Based on the engineering background of 8204 working face of Tashan Coal Mine 3~5# coal seam, this thesis studied the god-side entry driving technique. The reasonable width of coal pillar in 8204 trial working face was studied by using different methods: Theoretical Calculation, Numerical Simulation, Physical Similar Simulation, and Engineering Analogy. The reasonable support scheme was studied. The industrial field trial tested the reasonability of coal pillar width and suppot scheme.The study results shows: For extremely thick coal seam with top coal caving longwall mining at Tashan Coal Mine, lateral abutment pressure peak area is about 35 m, and stress relaxed area is about 0~10 m. The gob-side entry was located in stress relaxed area when the coal pillar width is 6 m. During the entry driving, the strata behaviors is not strong by using bolt-net-anchor coupling support strategy: anchor bolt + W-type steel band + anchor cable + 11#joist steel + combination cable + seiling surrounding rock by shotcreting, and the support parameters were choiced by comparing the additional stress of surrounding rock caused by different bolt and cable parameters; ribs convergence was less than 65 mm and roof to floor convergence was less than 55 mm, the stress of anchor bolt and anchor cable was small and stability of surrounding rock could be control easily; gob-side entry driving disturbed the gas in the gob, resulting in fluctuation of gas concentration and pressure difference. Fracture development in the coal pillar, and seiling surrounding rock by shotcreting could not solve the problem of gob air leakage. |
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