Support Technology Of Weak Cemented Soft Rock Roadway In Maiduoshan Coal Mine

With the adjustment of the overall layout of coal mining in China,the development of coal resources in Western China has become a strategic task of national energy.However,affected by many factors such as diagenetic age and geological environment,weak cemented soft rock is often encountered in the mining process of western mine.The surrounding rock of weak cemented soft rock roadway has obvious characteristics such as poor self-bearing capacity,long self stabilization time,variability,rheology,etc.the traditional roadway construction technology has been unable to guarantee the normal use of the roadway,so weak cemented soft rock well is targeted The research on the construction technology of roadway engineering is of great significance for the safe mining of deep coal resources in Western China.This paper takes the auxiliary horizontal car yard project of maiduoshan coal mine of Ningxia coal industry group as the background,through theoretical analysis,engineering analogy and field practice experience,the support scheme of weak cemented soft rock roadway is studied.The main conclusions are as follows:(1)Based on the analysis of the geomechanical conditions of maiduoshan coal mine,it is concluded that the main mineral components of the rocks in the mine are coal,gray siltstone,light gray siltstone,gray white siltstone,gray black siltstone and fine sandstone.The siltstone is relatively hard,and the fine sandstone is soft rock.The clay mineral content in siltstone is about 56.3%,and the content of quartz and feldspar in fine sandstone is about 68.1%.Through uniaxial compression,tensile and triaxial compression tests,Poisson's ratio,elastic modulus,cohesion,internal friction angle,dilatancy angle,uniaxial compression,tensile strength and other related parameters of various rocks in maiduoshan coal mine are obtained,and it is found that the strength of rocks after yielding is greatly reduced.Finally,the maximum horizontal principal stress,minimum horizontal principal stress and vertical stress of surrounding rock in maiduoshan coal mine are 26.2mpa,10.2mpa and 13.7mpa respectively.In the actual production process,it is found that when the deformation is not obvious,part of the surrounding rock will suddenly crack,spall and even fall,and the weathering resistance of the surrounding rock is weak;(2)The supporting scheme of weak cemented soft rock roadway in maiduoshan coal mine is designed.The roadway section is determined to be the type of smooth connection of arch crown,straight wall,arc side foot and reverse bottom arch.The net width � clear height = 5400 mm � 4300 mm.The supporting form is bolt mesh shotcreting + concrete-filled steel tube support.The anchor bolt is a screw steel bolt with a diameter of 20 mm � 2 200 mm,and the spacing between rows is 700 mm � 700 mm.The anchor support plate is Q235 steel,with the size of 150 mm � 150 mm � 10 mm.The metal mesh is made of ? 6.5 mm steel bar,with mesh size of 100 mm � 100 mm and shotcrete grade of C30.The top of the roadway is a single steel strand anchor cable with the model of oom15-1,which is anchored by resin cartridge.When installing each anchor cable,the amount of resin cartridge at the end is 4,the depth of the anchor hole is 7m,the aperture is 32 mm,and the length of the anchor cable is 7.2m.The tray size is ? 300 mm � 20 mm,and the row spacing is 1400 mm � 1400 mm.The two sides are long anchor cable bundles,three steel strands,and the model of anchorage is oom15-3,which is anchored with cement mortar.The depth of the anchor hole is 20 m and the hole diameter is 90 mm.The total length of the anchor cable bundle is 21 m,and the exposed length of the hole is 1m.The size of base plate is ? 300 mm � 20 mm.The type of steel pipe for concrete-filled steel tube support is ? 194 � 8mm steel pipe,with row spacing of 800 mm.The vertical reinforcement model is ? 22 mm,and the vertical thick reinforcement is divided into four sections,and the curvature varies with the support steel pipe of each section.The length of the steel bars in the two sides of the support is consistent with that of the steel pipes in the two sides of the support,and the length of the steel bars in the top arc section of the support is the same as that of the steel pipes in the top arc section of the support.The concrete arch body is sprayed with C30 concrete with a total thickness of 400 mm.Among them,156 mm behind the support wall,194 mm between the supports and 50 mm inside the bracket.The arch below the floor must be poured and vibrated after filling.Shotcreting is carried out above the floor;(3)The industrial test was carried out in the auxiliary horizontal yard roadway of maiduoshan coal mine,and the support effect was monitored.The measured surface displacement tended to be stable since the monitoring started,and the displacement was small and within the allowable range.Through the pressure box,bolt dynamometer and anchor cable dynamometer,the maximum compressive force of concrete arch around the roadway is only 17 kn.It is also measured that the stress of anchor rod and anchor cable is relatively stable,and the stress is small,which is 47 kn and 43 kn respectively.Nearly nine months after the completion of auxiliary horizontal yard roadway construction,it is found that the roadway floor has no uplift and deformation,and the support effect of reverse arch is good.The surface of roof and two sides is very smooth,and there are no cracks and deformations representing the deformation and failure of roadway.The supporting effect of roadway is good and stable,which indicates that the support scheme has certain reliability.