Optimization And Application Research Of Anchoring Scheme For Coal Mining Working Face Under Hard Roo

The safety of roadway excavation and the stability of support are the core to ensure safe production in mines.Due to the gradual deepening of mining,coupled with the complex and changeable geological conditions,the separation between the roadway support scheme of the mine and the actual mining has became more and more prominent,which puts forward higher requirements for the support design of the roadway.Taking the roadway of the second horizontal working face of a coal mine in northwest China as an example,the roadway anchorage scheme is optimized through field investigation,theoretical analysis and numerical calculation,and has carried on the field application.The main research contents and results are as follows:(1)Through the mine geological data,we have mastered the basic situation of the working face in the Mine,including the upper and lower comparison of the working face,the basic situation of 5 # coal seam,the condition of the roof and floor,the geological structure and hydrogeology in the section;(2)Three measuring stations are arranged in the excavated roadway of the 5# coal seam,using the hydraulic fracturing ground stress measuring instrument of type SYY-56 to collecte the pressure value in real time,and analyzing the resulting hydraulic fracturing curve and calculating the rupture pressure,retension pressure and instantaneous closing pressure of each station by software,and it is judged that the ground stress level of the 5# coal seam is generally a low stress zone dominated by structural stress,the regional vertical stress value in this area is between the maximum and the minimum horizontal primary stress.Through the measurement results of the station,it was judged that the stress direction of the 5# coal seam was roughly north-east,without major deflection,and the consistency was good.(3)In the three stations,using the surrounding rock strength test device of WQCZ-56 to carry out in-situ strength tests on rocks and holes within a certain range above the roof,and it was determined that the average strength of sandstone within 10 m of the roof was 101.35 MPa,which belonged to the hard roof,and the average strength of the 5# coal seam body was 16.74 MPa.(4)According to the actual needs of the mine,the transportation lane adopts a regular trapezoidal section with an alley height of 3.0m,a bottom width of 3.8m and a top width of 3.6m;the middle alley adopts a trapezoidal section with a lane height of3.0m;a bottom width of 3.25 m and a top width of 3.05 m,and the track alley adopts a rectangular section with an alley height of 3.0m and an alley width of 3.4m.Calculating the air volume of the working face and checking the wind speed of the section size;(5)According to the engineering analogy method,the support form of the three roadways was determined to be anchor beam network support;The supporting parameters of the three roadways were calculated by using the suspension theory and the combination beam theory,and it was concluded that the bolt specifications of the three roadways of the working face were Ф20×L2200mm,the specifications of the anchor cables were Ф21.6×L6300mm,the row distance between the bolts did not exceed 1.1m,and the row distance between the anchor cables did not exceed 3.8m.The Flac3 D numerical simulation software was used to simulate the two sets of support schemes of the three roadways,and the two sets of schemes were compared according to the stress field,the displacement field,the roadway surrounding rock deformation and the size of the plastic damage area,and the row distance between the bolts and anchor cables of the three roadways was determined,then get the final support scheme;(6)Support the roadway according to the determined support scheme,two measuring stations are set up at 100 m and 600 m of the three roadways of the working face,and the deformation of the surrounding rock of the roadway is observed by using GUD350 electronic roof separator and cross distribution method,the maximum distance of the two gangs of the roadway is 33 mm,the maximum amount of the top and floor approach is 52 mm,and the cumulative amount of roof separation does not exceed10 mm,which verifies the rationality of the support design and plays a good supporting role in the top and bottom plate of the roadway and the coal body of the two gangs.