Study Of Weakening Top Coal Using Water Injection In Fully Mechanized Sublevel Caving Mining Of Steep And Heavy Thick Coal Seam

Many coal seams of Urumqi mining area exist as steep thick coal seams. The mining with horizontal section top-coal caving of steep thick coal seam is an advanced method for coal mining and is widely used at present. While at the same time, the problem of top-coal weakening in large section and high level mining has received only limited attention and lacked of comparatively systematic research.The strata dip angle of Xiao Honggou coal mine is 87 ° ~ 89 °, the thickness of barren rock of sandstones and coarse sandstones is not stable and the thickness is 513.77 m and the minable thickness is 150.95 m. It contains 32 coal seams which are numbered B1~B32 from old to new. They are divided into four groups according to the features of coal seams. B1~2 is the first group and B3~6 is the second group which belong to heavy thick coal seam. This paper takes the fully mechanized coal mining faces +618 B1+2 and +590 B3+6 as background to research.This paper explains the determination experiments about the parameters before and after water injection of coal samples mined from the faces in the laboratory which includes hardness, porosity, water absorption, surface tension, uniaxial compressive strength, water contact angle, permeability and water absorption and weakening factor. In this paper, determination experiments about the effect of different composition solutions and different concentration solutions on the weakening property of the coal’s water absorption are conducted. Theoretical analysis about top-coal weakening is made according to the data experiment simulation through FLAC3 D and F-RFPA, on the basis of the parameter data collected in the experiments. Specific weakening implementing program is designed to solve the problem about the choice of control parameters and projection of fully mechanized top-coal weakening of steep thick coal seams in Xiao Honggou coal mine. The practice of the mining area shows that the application of water injection weakening and advancing explosion-proof makes the coals weaken significantly and meets the top-coal caving requirements. It improves the top-coal caving rate and reduces the risk of spontaneous combustion of coal and coal dust. Finally, the purpose of increasing yield and efficiency and safe mining has achieved.