| Tunnel gushing is a common project disaster which can result in consequencessometimes. It not only influences the normal construction of the tunnel constructionbut also spread to the safe operation after the completion of the tunnel. Jinping ⅡHydropower Station is the typical Landscape of Mountains and canyons which hasstrong mountains and high peaks,it have deep valleys and steep cliffs. It have beenoccurred to varying degrees of Gushing water more than200times sine theexcavation of the tunnel auxiliary hole, and generated a great deal of security risks tothe safety of personnel and equipment.What impact in order to reveal the tunnel site area groundwater environment, aswell as the impact of groundwater environment changes in the tunnel gushing by theconstruction of the Jinping hydropower station tunnel, it carried out the followingwork in this paper.（1） Investigation and analysis of geological conditions and hydrogeologicalconditions of the study area;（2） To establish the hydrogeological conceptual model;（3）Establish Three-dimensional numerical calculation model for the study area by themeans of numerical simulation in major;（4） Have a research on Three-dimensionalnumerical calculation of the groundwater flow of the tunnel site area, there havedesign of the following three-dimensional numerical simulation program:①Groundwater Flow Simulation in the natural state,②Groundwater Flow Simulationof water storage before the tunnel under drained conditions,③Groundwater FlowSimulation under the conditions of tunnel drainage after impoundment,④God flowfield calculation and analysis of all tunnel drainage tunnel closure conditions beforeand after impoundment,⑤Inflow of each period in the tunnel drainage conditionsbefore and after impoundment and computational analysis,⑥Displacementcalculation of the drainage tunnel drainage tunnel blocking conditions at various timeintervals before and after impoundment.The main results are as follows:（1）Complex geological structure in the region, and development of anticlines,synclines and the faults. Region groundwater types are divided into loose rock porewater in Loose Quaternary deposits layer, Carbonate rock fissure cave water and bedrock fissure water in three categories which to Carbonate fissure cave water’smain. In area limestone and marble in baishan group (T2b) middle Triassic are themajor rich and strong water-rock group; the main weak water-rich rock group includemarble of the under Triassic （T1）; marble and limestone of yantang group （T2y） ofmiddle Triassic and limestone of zagunao group (T2z) of middle Triassic; impermeablelayer is sandstone and slate of upper Triassic （T3）. Identified relations of Recharge,runoff and excretion in area, the major recharge is rainfall and mountain snowmelt,and through surface runoff or small karsts pipe to spring form to excretion to theYalong River and valleys of area.（2）Study on the basis of the above geological conditions and hydrogeologicalconditions, Generalization of the model boundary conditions and the sources andsinks of study area, establish hydrogeological conceptual model of the study area.（3）Obtain the initial groundwater level through the numerical calculation ofthree-dimensional steady flow of tunnel site. Then have a numerical calculation ofthree-dimensional transient flow of tunnel site, and analysis the seepage field underthe condition of complete drain before the reservoir storage. The results showed that:Excavation of the tunnel have a big effect of natural groundwater seepage fields fortunnel site under drainage condition, and have an obvious change for the law ofdistribution of groundwater around the tunnel, along the tunnel toward there formed“the long axis “drop-bit funnel and a large drawdown, especially for the groundwater ofsoluble rock strata.（4）Designed a simulation program in the tunnel block under the assumption,make a groundwater seepage field recovery simulation of tunnel site. Thethree-dimensional numerical results show that: tunnel excavation caused a big impactof the groundwater environment in tunnel address, and make groundwater seepagefield around the tunnel into a funnel-shaped, and also will have a long time affect.（5）Three-dimensional unsteady seepage numerical results show that the totalinflow of tunnel group is13.15m3/s, and the water inflow followed through theformation of tunnel is1.25m3/s in zagunao group (T2z) of middle Triassic,0.71m3/s inupper Triassic （T3）,8.89m3/s in baishan group (T2b) middle Triassic and2.30m3/s inyantang group (T2y) of middle Triassic, the results of Three-dimensional unsteadyseepage numerical results is good agreement with the tunnel actual gushing, it showsthat the model and calculation results are reasonable.（6）The results of this study have provide a reliable basis for the normaloperation of the tunnel of Jinping power station, and also important for the normalconstruction and safe operation of the tunnel-like. |
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