| Abstract:With the development of national economy, domestic demands of bauxite become more and more large. Bauxite is generally exploited by open-pit mining, with surface and easy mining resources are depleted, underground mining under complicated geological conditions has gradually become an important part of bauxite resource development. In this paper, San Men xia bauxite underground mine is taken for example, roadway excavation and support stability studies are carried out under complicated geological conditions. The ore body is buried under the riverbed, although the river course is changed, but the mine geological conditions is complicated, weak shale, fault, limestone fracture zone etc, have a serious impact on the speed of roadway construction. Therefore, in this paper, in order to solve roadway excavation and support problems, improve roadway construction speed, after consulting relevant research data, the main factors which affect the stability of roadway are comprehensively analyzed by geological survey and exploration, indoor rock mechanics experiments, theoretical analysis, numerical simulation and field tests. Corresponding research program which is aimed to solve the problems of roadway excavation and support has been proposed, the main research contents and results are shown as follows:(1) Distributions of adverse geological body which is ahead of working face are obtained by on-site investigation and detection, surrounding rock rebound strength tests are conducted, rock Q values are evaluated, advanced detection and analysis are carried out by TRT6000and TEM instrument. A new advanced prediction program which is consist of TRT6000and less advance drill is proposed, the new program will provide effective protection for roadway construction under adverse geological conditions. Survey results show that major problems which effect2th and3th shaft are limestone crushing area, shale weak areas and fault fracture zone, and the problems which is7th shaft faced with are shale weak areas, caves and groundwater.(2) After field sampling and samples processing, creep properties of main surrounding rock are studied by graded incremental cycle way, rock creep damage mechanisms and micro-crack propagation law are theoretically analyzed, rock creep empirical model is derivated by the experimental data. Rock total creep strain can be subdivided into instantaneous elastic strain ?me, instantaneous plastic strain emp, viscoelastic strain ?ce and viscoplastic strain ?cp, according to each creep component characteristic, an improved Burgers (Burgers) rheological model is proposed. Parameters of empirical model and improved Burgers model are identified by the method of least squares, the correctness of the model is verified by experimental data fitting, and it will help for roadway deformation numerical simulation.(3) Roadway excavation stress and displacement evolutions are analyzed theoretically, then according to the basic principles of rheology, mechanical analysis of viscoelastroplasticity is carried out for roadway stability. Faced with the main problems of roadway excavation and support, typical geological conditions are taken as research object, The model is established by MIDAS-GTS and imported to FLAC3D for calculation. The results show that maximum deformation and stress most concentrated area is located in the middle of adverse geological body which roadway pass through, and the location is also the worst stability area. For these areas, the support body strength increase and timely support measures should be appropriately considered. At first adverse geological body length which is along roadway direction will be detectd by TRT6000and some advanced drilling, so that the weakest area location of roadway will be identified for roadway excavation and support construction.(4) According to numerical simulation analysis and current support method, under the condition of ensuring roadway stability, in order to speed up roadway excavation and support, combination support method which is mainly with steel fiber shotcrete is proposed, the new method is used to replace cast-in-situ concrete support and the steel mesh, bolts will be properly considered in weak areas. Field industrial tests show that the stability of surrounding rock is ensured, construction speed is improved, it can clearly be seen that the new method have important application feasibility, reasonable spraying thickness will be choosen according to the actual situation of surrounding rock. Finally, for clay shale region, based on the current construction program, a new drill rod shed support method is proposed, the support method not only has advance support effect, but can also form a whole supporting structure together with secondary support. |
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