New bolting structure of fractured roof based on the Bossinesq equations

Present support theories contain a number of shortcomings in the designation of fractured roof bolt parameters of rectangular or trapezoidal coal roadways.Roof fall accidents occur easily in this kind of roadway.Based on the Bossinesq equations and the Mohr strength theory,we propose a theory of an anchored cluster structure for fractured roofs and have investigated the formation of such an anchored cluster structure,its self stability mechanism and mechanical properties.The results show that an anchor and the surrounding fractured rock can form a string-like supporting structure,referred to as the structure of an anchored cluster for rational bolt parameters.Not only can the structure maintain its own stability,but as well undertake the load of the overlying strata.The designated support parameters,based on anchored cluster theory can overcome the shortcomings of other support theories applied to a fractured roof of rectangular roadways or could not be calculated.Our anchored cluster theory can provide a theoretical basis for the design of support for rectangular fractured roofs.Furthermore,the theory will help to reduce the probability of roof fall accidents caused by local fractured rock blocks,which can destroy a supporting structure.