| With the in-depth implementation of the western development strategy, China’s construction of highways, railways focus has gradually shifted to the plains in mountainous and hilly areas, which will generate a lot of mountain tunnel,"long, deep" is typical of the mountain tunnel characteristics. The main factors restricting the development of the long tunnel boring technology, supporting technology, ventilation technology, poor geological. Most major constraints in the existing technical and economic conditions, adverse geological, tunnel excavation process may induce various types of geological disasters. Common tunnel geological disasters including soft rock fracture zone, lithology unconformable contact with groundwater, karst conduits, karst collapse, goaf and rockburst. Tunnel gushing disaster is a difficult problem in the construction of the tunnel project, at home and abroad have been built many serious gushing accident have occurred in the tunnel, large-scale water gushing often cause huge economic losses and casualties. Have embarked mountainous karst tunnel gushing disaster the study of the mechanism of long tunnel gushing disaster prediction and prevention has important theoretical significance and engineering practice significance.With the Wu-chi-ba Tunnel of Hurong Freeway as the research object, using a combination of theoretical basics of the related disciplines of geology, hydrogeology, rock mechanics, groundwater dynamics, combined with mathematical statistics, nonlinear theory, numerical simulation and mathematical analysis method, trying to establish the tunnel’s gushing Wuchiba Geological model from the karst development master factors and the instability mode angle; gushing groundwater dynamics perspective of evolution from the tunnel on this basis, combined with catastrophe model to explore the karst tunnel gushing disaster mechanism Its mechanical evolution; experience computing model and numerical calculation model combining quantitative analysis means the tunnel Wuchiba inflow predict comparative analysis on a variety of forecasting methods; Finally, using orthogonal experimental and regression analysis a combination of methods to explore the safe distance between the overlying and underlying type and side-volt type karst tunnel and cave and its influencing factors, to establish a safe distance and influencing factors of three karst tunnel mathematical prediction model. Through the above analysis and research, made the following conclusions and results:(1) karst development by factors such as lithology, groundwater dynamic zonation, geological structure, topography control, including the formation lithology, geological structure is led hydrodynamic conditions is the decisive factor.(2) the irruption water impact factors can be summarized into two kinds of geological factors and engineering factors. Geological factors, karst aqueous medium usually with heterogeneity and diversity, and water distribution is very uneven, laminar and turbulent coexistence, small fissures constitute the main water storage space; large corrosion fissures constitute a major water guide channel. Engineering factors, rock excavation unloading, blasting disturbance and grouting failure are the master of influencing factors, caused largely the water inrush lag and uncertainty.(3) The water from karst essentially system of karst aqueous medium, the equilibrium hydrodynamic system as well as the surrounding rock mechanics changed dramatically Underground Excavation, instantaneous release of energy stored in the groundwater bodies and fluid form of high speed engineering migration a driving force to undermine the free surface phenomenon. View from the water-rock interaction mechanism, the the irruption water contains two process stages, poised mechanism of water from karst and karst water inrush mechanism of instability, of which the former is a long historical process, the latter is the former energy savings instantly mutation form.(4) energy storage containing hydraulic conductivity structure, karst hydrodynamic disturbances and energy release with Derivative the water structure system instability angles proposed the occurrence of water from karst conditions, and irruption water process is divided into two poised and destabilization significant stage; flow pattern evolution characteristics of multi-field coupling software calculates the excavation under the conditions of water from karst formation process, the development of karst water from the aquifer seepage rapid flow of potential water inrush channel, and finally broke into the tunnel formation The free flow catastrophic evolution process.(5) analysis based on the different causes of geological defects classified and water barrier properties proposed geological defects induced water inrush two typical catastrophe mode analysis of geological defect type the sudden water channel formation process and its instability mechanical criterion. Differences in the permeability characteristics of different scale geological defects, the of strong seepage action filling media penetration instability model and filling slip instability of water inrush model, and applied to Wuchiba tunnel karst conduits induced water inrush instance analysis, combined with the results of numerical analysis, to reveal filling the media penetration instability formation blockage body after the overall slip sudden water cataclysm evolution; consider water for non-conducting faults, the mechanical properties of the two-section filling medium, the introduction of water-borne The weak function reflects the strong seepage on the activation of the fault filling medium, the establishment of a fault backfill slip instability swallowtail catastrophe model and control parameters based on the catastrophic evolution path analysis to propose appropriate prevention and control measures. Based on a large number of numerical results, analysis, fault reactivation induced rupture channel catastrophe mechanism, the inrush of water catastrophe path analysis and fault parameters of the sensitivity of the water inrush. Finally, expose water inrush mode-based catastrophe analysis proposed composite water inrush type analysis of geological defects induced instability impermeable wall rock the catastrophe of the non-exposed water inrush mechanism and engineering instance, further reveals the fault activation The conduction dark river water influx tunnel caverns filled hydraulic connection exists, and cause catastrophic evolution mechanism of the arch of the tunnel the complete surrounding rock fracturing water inrush.(6) analysis through Wuchiba tunnel hydrogeological conditions, to using the "Visual MODFLOW2.7.1" Three Dimensional Seepage analog and conventional empirical formula forecast inflow of Wuchiba tunnel, and its results were analyzed to ensure that the predicted results reliability. The entire tunnel Wuchiba tunnel smallest inflow between12000～22000m3/d,, normal (construction period average year) between24000～47000m3/d, large value (construction period wet years) in the30000～96000m3/d.(7) orthogonal test program FLAC3D numerical simulation analysis of the safe distance between the overlying and underlying and side-volt karst tunnels and caverns, Rock Classification rock side pressure coefficient, cave span the caves high-span ratio and tunnel depth of five influencing factors affect the extent and impact of the law on the safety distance. Safe distance for overlying and underlying karst tunnels, caverns span large cave high cross is smaller than the safe distance; side Volt karst tunnel, cave high cross than the safe distance, small cave span safe distance, that is perpendicular to the direction of the cave size of tunnels and caverns connection safety distance and parallel to the direction of the cave size of tunnels and caverns connection safe distance than small.(8) Univariate regression analysis showed high cross than the overlying and underlying karst tunnels, tunnel and cave between the level of safety distance with the surrounding rock and rock mass lateral pressure coefficient exponential relationship, span and cave and cave a linear relationship with the logarithmic relationship; tunnel depth karst tunnel side Volt safe distance between the tunnel and cave Rock Classification exponential relationship was quadratic polynomial relationships with the rock side pressure coefficient, cave span and cave high cross than a linear relationship between logarithmic relationship with tunnel depth. On this basis, the overlying and underlying type and side-volt karst tunnel safe distance above five impact factor mathematical prediction model by multiple regression analysis. |
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