Technology Study On Bolting Support Stiffness And Preload Of Mining Roadway

Along with the improvement of roadway supporting technology and development of anchoring theoretical level constantly, the application technology level of anchor support stiffness and pre-stress anchoring support are improved continually, being used widely in many underground engineering field, such as tunnel, architecture, mine etc. In recent years, along with the rapid development of economy, the demand for coal resource is gradually increasing. Because exhausted shallow coal resources cannot satisfy the needs of economic development, coal mining had to turn to deep mining. The traditional bolting support techniques have not been adapted to modern deep roadway mining. High stiffness, high strength of pre-stressed anchor constitutes modern bolting support system, providing an efficient way for safety, fast and economical mining.Reasonable supporting stiffness can effectively control surrounding rock deformation within permitted range, and avoid excessive deformation to damage the bearing strength of surrounding rock. Anchor pre-tightening force is an important index about reflecting bolting initiative and timeliness, playing a key role on the roadway support effects. Reasonable pre-tightening force can improve the strata of the support ability, guarantee the bolting system exert support efficiency. Based on analysis the surrounding rock failure characteristics, this paper researched the mechanism about stiffness of bolting, bolt pretension force with roadway, and the mechanical characteristics of pre-stressed bolt, coming to a conclusion that the bolt axial force and cohesive force present negative exponential distribution on the anchoring section. Through analysis the factors of the anchor supporting stiffness and research the relationship between stiffness and rock, it obtained the main affecting factors of anchor supporting stiffness: the length and density of bolting, the fit of bolt diameter and boring diameter, the length of bolting section, the applying force of bolting pretension, the coupling of bolt and cable material properties etc. By analysis the factors of pre-stressed bolt supporting and research the relationship between preload and pre-torque, it is linear relationship between preload and pre-torque. Under the same bolting diameter, the scale factor k was significantly reduced by putting on gasket. In the conditions of different anchor pretension, through the numerical simulation for stress field distribution generated by pre-stressed bolt and the deformation and destruction of the surrounding rock, it comes to a conclusion that the deformation of surrounding rock was reduced continually with the increasing of bolting pretension. Finally, through detecting roof lithology by rock detection recorder, testing the rock loosing zone and pressure observation, analysis the force situation of roof and two sides of roadway, on this basis selecting reasonable supporting parameters of anchor support stiffness and pretension evaluate the stability of surrounding rock and support effect. The surrounding rock deformation and bolting effects get a satisfactory condition.