Study On Interaction Of Rock Undergroud Cavern And Slope

Underground cavern include the natural underground vacant areas (for example, karst cave), underground mined area formed in the mine production progress and artificial cavern because of manual excavation (for example, air defense cave and tunnel). The research of influence between underground cavern and slope appears along with the development of engineering construction. According to the formed sequence of the underground cavern and slope, the relationship of them can be divided into two conditions. The first condition is that the underground cavern had existed before the slope excavation, such as the mined underground area under the excavation slope in the case of underground mining converted to surface mining. The second condition is the slope had existed before the underground cavern formed, such as the tunnel excavation in mountainous areas. The research of interaction between the underground cavern and slope can be divided into two aspects. The one aspect is the influence of underground cavern on slope, the other aspect is the effect of slope excavation on underground cavern. In addition, the other important problem which is result from the relative tertiary location of underground cavern and slope is the safety roof thickness of underground cavern. The safety roof thickness relates to the safety and normal operation of underground cavern and even determines the stability of slope. In this paper, the author studied deeply the interact between the underground cavern and slope and the safety roof thickness, combining with the three projects: the project supported by HuNan provincial natural science foundation of China " (07JJ6084) , doctoral subject special fund of university in China (20060533071) and the project supported by HongFu company of GuiZhou province "the influence research of underground mined area on surface mining of WenFu phosphate mine". The main contents of the dissertation are summarized as follows:The calculation models were built which were applied to the analysis of deep-buried and shallow-buried rock cavern under the slope, the round shallow-buried cavern's stress analytic solution was derived by elasticity theory and complex function method, the deep-buried cavern was regarded as a stress concentration problem of biaxial compression infinite plate pole and the analytic solution of stress was gotten. For complex shape rock cavern, the Christoffel-Schwarz integral, approximate method or numerical method were used to analyze the stress and strain.The interact between the underground mined area and the slope in WenFu phosphate mine was researched and analyzed by elasto-plastic finite element method of lowing material's strength safety factor using my own two-dimensional FEM program, the effect of the underground mined area and the open pit slope was simulated in the slope excavation process and the stress ,the strain , the distribution of plastic zone and the safety factor of the underground area and the slope were gotten by analysis.The model of simply supported beam and the model of clamped-clamped beam which are often applied to estimate the safety roof thickness of the underground cavern were improved by considering the influence of horizontal stress of beam end on safety roof thickness, the improved beam models were built on the condition of concentrated force and uniform load acting on the beam by structural stability theory. The rock was looked on as perfectly elastic-plastic material and the relationship of the generalized moment-curvature-axial force was established and the equation of the generalized moment-axial force-lateral uniform load was built through the approximate solution method in which the beam deflection curve was assumed. For fractured rock mass, the fracture of rock was regarded as initial damage, the roof rock mass with random distribution fracture was researched, the equivalent deformation module and the poisson ratio of fracture rock mass were deduced and the effect of fracture density on the roof thickness was analyzed.The catastrophe models of underground spherical cavity and tunnel were established with catastrophe theory and the necessary and sufficient condition of roof failure was derived. The analysis shows that the underground cavern roof thickness is related to rock elastic modular, poisson ratio, cavern span, roof dead weight, the load acting on the roof and horizontal stress of roof end.The dynamic response of roof on which vehicle load act was researched regarding the vehicle load as harmonic load. The conclusions show the resonance happens whenω₁ = Q_p and the dynamic amplification factor depends on the vehicle velocity , the vibration response is larger while the driving velocity is slower when the vehicle drives on the roof with the same velocity only considering the model's basic vibration type. On the condition of general damping, the dynamic amplification factor depends on damping ratio (ξ₁) and the dynamic response when the vehicle drive on the roof with the same velocity is only half dynamic response when the vehicle is fixed to the roof mid-span. The catastrophe theory model of roof failure was built when the vehicle platoon acts on the roof and the necessary and sufficient condition of the roof failure was derived. In order to analyze the influence of calculation model, the roof was looked on as unidirectionally or rectangular thick plate model and the roof dynamic response was calculated, the effect of different boundary conditions was analyzed and the dynamic amplification factor was gotten with the vehicle vibration load.The underground mined area's roof safety thickness and its stability were analyzed by using FLAC^3D method and lowing material's strength safety factor method, the influence of the underground cavern's mining height and its span on the slope's stability was calculated. Taking the underground mined area and surfacing slope in the WenFu mine for example, the 3D geological model of the underground mined area was established with SURPAC software, the interface program of the model to FLAC^3D was written and the displacement and stress monitoring points were set in the underground mined area and the slope, the interaction betweem the underground mined area and open pit slope was researched with introduced 3-D geological model into FLAC^3D calculation program.Stood at the front of science research, the interaction between underground cavern and the slope is studied in the author's dissertation using newly numerical methods and means in the course of research work. It shows a high theoretical and practical value.