| The stability of surrounding rock of roadway with top coal in thick coal seam is a special maintenance problem which restricts the safe production of mine.Taking the 7302 auxiliary transport roadway of baodian coal mine as the research object,nearly 5m top coal is left along the bottom tunneling,and the roadway is in an asymmetric state on both sides,which are solid coal and 40 m boundary coal pillars respectively.The coal body fissure is developed in the roof at a depth of 2m,and the separation occurs at a deeper part of the top coal.The high side pressure of boundary pillar is more serious than that of solid coal.Based on the preliminary field investigation and laboratory test to determine the physical and mechanical parameters of coal and rock specimens,combined with theoretical analysis and numerical simulation methods,this paper puts forward the high-efficiency long anchorage and large spacing control technology,which has been successfully practiced in industrial tests.The following main conclusions are drawn:(1)A simple mechanical calculation model was established to study the disconnection mechanism of top coal in 7302 auxiliary roadway,and the total deflection of each layer was calculated by using the superposition principle of forces,so as to judge the deflection difference of each layer and determine whether the disconnection occurred between layers.Matlab software was used to analyze the influence of different cross-height ratios on the stability of top coal under the same excavation conditions.The vertical stress in the shallow part of the top coal was distributed in an "M" shape.Under the influence of large boundary coal pillar,the vertical stress level of coal pillar side is higher than that of solid coal side after roadway excavation.(2)The FLAC3 D simulation results show that the stress distribution in the boundary coal pillar is mainly determined by two major factors: roadway excavation and goaf.Under different top-coal thicknesses,the stress distribution trend along the xdirection of the tunnel in the model is roughly the same,with slight differences limited to the size and location of the vertical stress peak.No matter what kind of top-coal condition,the subsidence amount of the inner roof in the 0-3m horizon is large,and the subsidence amount of the inner roof in the 4-6m horizon is small,which shows that 3m is the key horizon,and the physical property of the coal above 3m horizon is similar to that of the rock mass.(3)The control technology of high-efficient long anchorage and large interval row spacing has more obvious advantages in the performance of single bolt than the original support.The stress level of 3.0m bolt support simulation is 0.5mpa higher than that of 2.4m bolt support simulation.In terms of roof surface subsidence,the moderating ratio of roof subsidence with 3.0m bolt and 2.4m bolt is 34.2% and 23.8%,respectively,compared with that without support,and the maintenance effect of long bolt is good.(4)In the industrial test,the roof surface of the 3.0m large bolt support section is more complete than that of the original support section.No obvious separation is found in the surrounding rock during excavation and stoping.During the stoping period,the final subsidence of the roof of the large bolt support section is about 40mm~50mm,and the final subsidence of the roof of the original support section is about 100mm~150mm.There are 61 papers,9 tables and 98 references... |
