Design And Experimental Study On Truss-Bolt System Support Of Surrounding Rock Anchor In Mine Engineering Roadway

In recent years,mine engineering in China has mostly adopted the underground mining method.Rectangular roadways have been widely used due to their advantages of high space utilization,convenient excavation and support,and rapid advancement of the mining face.With the increase of mining practice and the deepening of theoretical research,the theory of bolt support has made great progress.The Truss-bolt system is developed from bolt support,which can improve the stress state of the roof,improve the stability of the roadway roof,reduce the cost of roadway support and increase economic benefits.However,the existing design method has certain defects,which limits its application in engineering practice.In this paper,the Ningtiaota Coal Mine S1231 auxiliary transportation channel is used as the engineering support.The combination of theoretical analysis,numerical simulation and industrial test is used to design the supporting parameters of the Truss-bolt system,analyze the stability of the surrounding rock and evaluate the supporting effect.This article mainly draws the following conclusions:(1)The Truss-bolt system is a roadway roof support system composed of inclined anchor rods and horizontal tie rods connected by supports,which is equivalent to external reinforcement of the roadway roof,which is beneficial to form the Truss-bolt system support structure with the roof rock to strengthen roof stiffness of roadway.(2)Analyze the type of the Truss-bolt system and its action mechanism,and establish a mechanical model based on the characteristics and action mechanism of the Truss-bolt system structure.The classic rock pressure theory and the overall structural calculation method are used to calculate different types of Truss-bolt system structures.According to the roadway roof strengthening rock beams without shear failure,the minimum reinforcement thickness of the rock beams is determined.According to the fact that the rock beam on the roof of the roadway does not undergo tensile damage,the configuration of the horizontal tie rod of the anchor bracket is determined,and the theoretical expressions of the reinforcement thickness of the Truss-bolt system structure and the pretension of the horizontal tie rod are derived.(3)Establish the stability criterion for the roof of the roadway supported by the Truss-bolt system.Taking the single-type Truss-bolt system structure without intermediate anchor as an example,the influence of the thickness of the rock beam strengthened by the roof roof and the pretension of the horizontal tie rod are analyzed.Factors,it is obtained that the pretension of the horizontal tie rod is directly proportional to the roadway span,roadway height,cohesion and bulk density of the surrounding rock,and inversely proportional to the height of the rock beam section reinforced by the roof and the friction angle in the surrounding rock of the roadway.(4)According to the proposed design method,the supporting scheme for the auxiliary transportation along the S1231 working face of the Ningtiaota Coal Mine was designed.The numerical calculation model of the Truss-bolt system and traditional bolt support roadway is established,and the industrial test section is selected for the Truss-bolt system support test,and the roadway section convergence is monitored.According to the comparison and analysis between the numerical simulation and the field measurement results,the convergence of the roadway section supported by the single-type Truss-bolt system and the double-type Truss-bolt system support scheme with intermediate anchor rods is within a reasonable range,and the stability of the surrounding rock of the roadway can be satisfied safety production requirements.