Research On The Roof Failure Mechanism And Support Technique Of Roadway In Ultra-km Layered Hard Rock Mass

In order to meet the development requirements, Woxi Mine subordinated to Hunan Chenzhou Limited Liability Company has adjusted the mining depth, which has reached1025m and will extend to a depth of1400m gradually. The main development tunnels are mostly laid out in the layered sandy slate which are thin and hard. In addition, the original supporting scheme is rather rough, the whole construction organization is disordered, and the rehabilitation cost is quite high. All of these factors have led some roofs of the tunnels to serious damage and deformation. Therefore, the old method has been unable to support the tunnels in ultra-km layered hard rock mass, which directly impacts on mine production capacity and hinders the normal development of enterprises as well as the further improvement of economic benefits. To counter the existing problems, the thorough research has been conducted into the roof failure mechanism and support technique of roadways in ultra-km layered hard rock. A great many research methods was adopted in the thesis, such as mechanical analysis, rock mechanics experiments, numerical simulation and field test methods. Specific researches are as follows:(1) The conventionally physical and mechanical tests on the sandy slate were experimented. Besides, by means of measurement and calculation, distribution rules of crustal stress in Woxi mining area have been gained.(2) Through two mechanical model including level composite beam and inclined thin plate fixed at both ends, the failure mechanism of level and inclined layered roofs is analyzed. The research results show that the strata subsidence is greatly affected by thickness of strata, vertical uniform load, stratum span and angle.(3)The roadway excavation in layered hard rock mass has been simulated and analyzed by utilizing the numerical simulation software3DEC. Moreover, the deformation and failure of the roof and surrounding rock have been analyzed in different conditions, such as with different thickness to length ratio, different angles of rock stratum and different lateral pressure coefficients. With the measuring points monitored and analyzed, many characteristics can be seen clearly, which include deformation of the surrounding rock, slide and failure of the rock stratum as well as the plastic zone distribution.(4) Considering the basic situation of Woxi mining area and the existing support deformation, a series of researches, tests and analysis has been carried out, from investigation of roadway joint fractures, deformation monitoring to a new excavation roadway, broken zone monitoring to a new excavation roadway, determination of support parameters, design of energy absorption anchor, to construction technology. After the comprehensive analysis, combine all those factors with the conclusion of numerical simulation together and finally a asymmetric support and construction technology which is safe and reliable was proposed.