Research On Rockburst Roadway U-Steel Support Of Stress Character And Deformation And Failure

Rockburst is one of the major disasters in coal mining. The study found that, most of rockbursts occur in the roadway. U-steel stents have been widely used in the coal mine roadway supporting. And the U-steel supporting has always been a hot and difficult problem for the experts and scholars. While, the study on stress character and deformation and failure of U-steel supporting for rockburst roadway is rare. The methods of combination of theoretical analysis, laboratory test and numerical simulation are used to analyze the propers of U-steel stents.The mechanical calculation of U-steel stent is done through theoretical analysis.The bearing capacity characteristics and deformation and failure of U-steel stent are researched through laboratory test and numerical simulation.The deformation and failure types of U-steel supporting for rockburst roadway are summarized. They consist of stent lapped segment failure, non-stent lapped segment failure and comprehensive failure. The failure reasons are analyzed, and the key roles are the relationship between support and surrouding rock and the clamp of stent lapped segment.The mechanical calculation model of circular U-steel support for rockburst roadway is simplified, the U-steel stent shrinking criterion is put forward. The U-steel stent internal force is analyzed from three aspects like clamp pretension, external load and after-shrink, then the total internal force of U-steel stent is obtained.Through laboratory test and numerical simulation, the mechanical propers and deformation and failure of U-steel stent are analyzed. The research of stent lapped segment shows that:In the process of U-steel sliding, the axial load carrying capacity of U-steel stent lapped segment is unstable and intermittently dipped. A sudden dislocation occurs between clamp screw and U-steel, the contraction performance of stent lapped segment is unstable, and the greater the nut torsion, the more frequently the dislocation occurs. The numerical simulation shows that, in the process of U-steel sliding, the clamp screw leans and produces additional bending moment, which results in the local stress concentration. And when the load exceeds its ultimate strength, the fracture of clamp screw occurs, then lapped segment screw is failed.The research of U-steel stent shows that:Under the impact loading, the slip phenomenon of stent lapped segment is serious, the contraction of stent model is bigger, and the rupture failure occurs near stent lapped segment. The numerical simulation shows that, under local loading, U-steel wing plates are easy to open on both sides, occur yielding failure, and the clamp bolts appear weak areas through tensile deformation. After U-steel wing plates strengthening, the U-steel stent changes from semicircle to rectangular,and the top of U-steel stent changes from arch to "?"-shape.