Study On Failure Law And Support Technique Of Straticulate Roof Of Hard Rock

Roof caving is one of the most serious engineering disasters in underground mining activities of metal mines. It not only delays the progress of production, but also threats against underground workers. Owing to the less common distribution of layered roof in metal mines, the research of the support of hard rock layered roof is relatively less and still at the initial stage. The instability mechanism and supporting of hard rock layered roof are studied based on the project of layered roof supporting in Cangshan iron mine in China Steel Group. And the reasonable support solution is proposed, which could be of great theoretical significance and engineering guidance. The research works mainly include:(1) Through the theoretical analysis, the hard rock layered roof of stope is simplified as plane strain plate by the application of thin plate elasticity theory. And the formulas of the critical loads and the critical stress of rock beam failure are derived under the boundary conditions of beam simply supported and fixed supported at both ends;(2) By use of FLAC 3D numerical simulation, the failure law of hard rock layered roof in the depth of 50～300m is studied, with the variation of different factors of overlying strata, such as roof layer thickness, strata type, orebody depth and so on;(3) The principle of special support, support methods and theoretical design basis of deformation resistance of hard rock roof are proposed;(4) Taking the engineering project of Cangshan iron mine inChina as a case, the relationship between layered roof caving and geological conditions is analyzed through field investigation. And the stability of the rock in stope is evaluated combined with the rock mechanical tests in Cangshan iron mine. Then three kinds of support methods are designed as joint support of resin anchoring bolt and extended resin anchoring bolt, joint support of resin anchoring bolt, extended anchoring bolt and strip, joint support of mortar bolt and anchor. The optimal supporting method is determined through the numerical simulation of the supporting effect of the methods.