| The section of Changsha-Kunming railway line in the western of Guizhoulocates in the center of Yunnan-Guizhou plateau, which belongs to the intersectionportion of Yangtze platform and South China platform. In this area, the geologicaltectonic develops strongly; valleys cut deeply and Carbonate rocks are wide spreading.Influenced by complex geological environment and hydrodynamic conditions, karstdevelops well with complete types and rich medium types.The soluble rock section of10key tunnels of the line accounts for75%percent.In the condition of complex hydrogeology, water gushing of the tunnel andenvironmental hydrogeology problems are very prominent. As a main researchmethod, when applied in groundwater migration rule, the numerical simulation meetslots of problems in complex karstic conditions, as follows:1, it is hard of finding asuitable method to generalize the karst medium, for the diversity of karst mediumforms and the complexity of spatial combinations;2, complex karst hydro-geologicalconditions make it is difficult to accurately express the hydro-geological generalizedmodel.Therefore, choosing typical karst tunnels as examples, this paper studies thegeneralized methods of the karst medium and hydro-geological conditions in karstareas. Generalized methods of different karst mediums are studied based on thecontrast analysis between different karst mediums and the hydraulic characteristics ofeach subroutine bag in Modflow. Underground rivers are generalized as rives in themodel. Karst caves’ zone is generalized as the anisotropic medium with high verticalhydraulic conductivity, small specific yield and high porosity. Faults are generalizedas anisotropic units with vertical, high hydraulic conductivity and high specific yield. Through the analysis of hydrological geological condition characteristics in karstareas, The method of building a hydro-geological generalized model is studied frombuilding spatial structures, choosing factors, assuring boundary conditions andhydraulic conductivity.Dadu mountain tunnel is the one with the most complex karst hydro-geologicalconditions, whose geological structure develops strongly with7regional faults in5kilometers. In the tunnel zone, karst develops typically with obviously verticalzonality and plane regionalization, and geographic and geomorphic changes fiercelywith750m deep cutting valleys and high mountains. After further research on karsthydro-geological conditions in Dadu mountain tunnel zone, using the abovegeneralization method to establish a three-dimensional numerical model. Afterverifying the reliability of the model, water inflowing into the tunnel is predicted to be121766m3/d in dry season,170840m3/d and12.28m3/d m in rain season. Theinfluence of the tunnel construction on the neighboring groundwater environment issimulated.Through modeling practice of typical karst tunnels in the section ofChangsha-Kunming railway line in the western of Guizhou, this paper provides areliable basis for water proof and drainage design of the karst tunnels, a generalizedmethod according with karst medium characteristics for the numerical simulations inkarst areas and make the application of Modflow expands to complex karst mediums. |
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