Study On Synergism Support Technology Of Different Excavation Method In Coal Mining Face Tunnel Of Layered Surrounding Rock

With the increase of the output and efficiency of the underground mining coal resources,the production equipment shows the characteristics of large-scale,the cross-section size of the coal mining face tunnel increases correspondingly,the span of the transportation and ventilation roadway is between 4.5 m-6 m,while the span of the coal mining face tunnel in the working face is between 7 m-10 m.There are few studies on the stability of the large-span coal mining face tunnel with layered surrounding rock mass,and the control of the surrounding rock of the large-span coal mining face tunnel is becoming more and more serious with the increase of the production capacity and span of the working face.These tunnel props have the characteristics of large deformation and separation,which is not conducive to the stability and control of the surrounding rock,especially the large-span coal mining face tunnel surrounding rock from the shallow to the deep and gradually separated from the layer cracks through each other.It is of great significance to study the stability and control technology of large-span coal mining face tunnel of layered surrounding rock mass for high-yield and high efficiency of coal enterprises.In order to improve the supporting effect of large-span coal mining face tunnel in Wanli No.1 mine,this paper takes 207 layered surrounding rock mass the coal mining face tunnel as the research object,analyzes the characteristics of surrounding rock damage,driving ideas and supporting technology.First of all,in order to understand the engineering geological conditions of the slicing tunnel with layered surrounding rock mass,it is found that the surrounding rock conditions of the direct rock strata are complex,showing the development of joint fissures,weakening of fissure water and destruction of surrounding rock,which is easy to induce the bad state of the roof separation of the slicing tunnel and have a bad impact on the production and driving.In order to further study the problems of the slicing tunnel on site,it is necessaryto FLAC3 D numerical simulation is used to analyze the failure characteristics of the surrounding rock under the condition of not supporting,and the deformation and instability characteristics of the coal mining face tunnel caused by the cohesion of multiple structural planes,internal friction angle and surrounding rock seepage factors.The surrounding rock shows the characteristics of unbalanced stress,high deformation and wide range of plastic failure.Then,in order to calculate the roof caving height more accurately,according to the existing roof beam structure caving literature,this paper analyzes the damage range of different parameters to the roof surrounding rock of the coal mining face tunnel with layered surrounding rock,and applies the mechanical equation of roof stability to calculate the roof caving height of the coal mining face tunnel as 5.595 m.The influence of the number of bolts and cables with different length on the roof subsidence of the tunnel is analyzed by using the related mechanical modeling formula.The cooperative support scheme of prestressed steel bolt + steel mesh+ anchor cable + steel belt + single hydraulic pillar and the measures of roof water diversion are determined to control the surrounding rock deformation of the large-span tunnel.Finally,on the basis of determining the support scheme,optimize the excavation mode of the coal mining face tunnel with layered surrounding rock mass,simulate three excavation schemes,compare the stress and deformation indexes of surrounding rock,select the first excavation support of 5 m,and then 2.6 m.The excavation and support method has little interference on the surrounding rock.The field drilling peep and anchor cable stress monitoring show that the support is in good condition,which provides reference for the excavation and support of the remaining coal mining face tunnel in the mine.