| Water gushing of tunnel tend to cause more serious consequences, it not only affect the normal construction of the tunnel, and will affect safe operation after completion of the tunnel.Daao tunnel zone is the typical Landscape of Mountains and canyons which has strong mountains and high peaks. Karst area tunnel water inflow forecast has been in the process of tunnel excavation and operation to solve the problem, and accurate prediction of tunnel water inflow on the personnel and equipment safety in the process of tunnel excavation is extremely important. In order to reveal the impact of groundwater environment of tunnel site area in the construction of Aaao tunnel, and the change of the groundwater environment of tunnel water gushing, it carried out the following work in this paper.(1) Investigation and analysis of geological conditions and hydrogeological conditions of the study area;(2) To establish the hydrogeological conceptual model;(3) Establish Three-dimensional numerical calculation model for the study area by the means of numerical simulation in major;(4) Have a research on Three-dimensional numerical calculation of the groundwater flow of the tunnel site area, there have design of the following three-dimensional numerical simulation program:①Simulate the groundwater seepage field in the natural state;②Under the condition of complete drainage after tunnel excavation, simulate the groundwater seepage field;③Under the condition of completely drainage after tunnel excavation, simulate and predicte the water gushing of tunnel, and combining with theoretical method to calculate the tunnel water inflow to compare and analyze tunnel water inflow;④Simulate the groundwater seepage field’s recovery under the condition of tunnel block.The main results are as follows:(1) Tunnel site area lithology is mainly limestone and sandstone. The upper tunnel entrance cover sandstone and sandy shale, and it is the typical karst area, and export section of the tunnel is clear empty hole of karst development for qingxudong fin limestone of bare karst area. The main strong rich water rock group of tunnel zone is cambrian qingxudong fin limestone, and the moderate to weak aqueous rock group is cambrian jindingshan fin dolomitic limestone and sandstone, the relative water-resisting strata is cambrian jindingshan fm arenaceous shale.(2) The resistivity method is adopted, and discussed the rock permeability and rock mass integrity characteristics. Tunnel in vertical and horizontal resistivity have very big difference, especially in the horizontal direction. Tunnel entrance resistivity is highe, explaining import period of rock is complete, and porosity is small, and the rich water-based is weaker. Tunnel exist section of resistivity is low, explaining the rock is broken, karst fissure is development, and watery is strong. The resistivity method can make a qualitative analysis of tunnel water gushing conditions.(3) This paper analyzed the hydrogeological conditions of tunnel site, sketched out the hydrogeological conceptual model of hydrogeology conditions in this area, determined the groundwater seepage model’s boundary conditions of the tunnel site area, and discreted time and space of the model. Establish the three-dimensional numerical model of natural seepage field on the tunnel site area of Daao tunnel. Through the water balance fitting and the observe water fitting, prove the credibility of three dimensional numerical model.(4) Tunnel complete drainage form a around the tunnel parallel linear drawdown funne, and at the same time it is also cyclical because of rainfall periodic change in a hydrological year. When the rainfall increased in the summer, the drawdown of export period decreased. It may make export section water inflow larger. From the perspective of the seepage field change of tunnel import and export section, the change of seepage field in the tunnel export section is much bigger than import section. After drainage90days, the water level of tunnel inlet mainly remains the same, and the maximum drawdown of water level of inlet is5m or so. Reason may be that the tunnel entrance overlying is sandstone and sandy shale, and permeability coefficient is little. Because the buried depth is shallow and it is located at the terrain slope, water inflow is not abundant; Due to large groundwater buried depth and higher water level, the influence of tunnel drainage of groundwater is the largest in central tunnel; in karst development section, the permeability coefficient is high, and groundwater closely related to rainfall, the influence of groundwater seepage field drainage around the tunnel is wider range.(5) Seepage field recovered significantly after blocked90days. The linear landing funnel of central tunnel began to disappear. Tunnel inlet water level differ with natural is only about2m,10m differ with natural water level at the exit, central tunnel differ about30m. After blocked180days, the tunnel seepage recovered quickly, and the entrance tunnel is recovered slower, the drawdown of import section near central tunnel is about20m. After blocked270days, most of the regional basically recovered to80%of the natural state. Seepage field basically return to the initial state blocked1years later. Overall, the the seepage field at tunnel export section recovered faster, but import section recovered slowly. This is because the tunnel site area is in the karst area, although the import section belongs to karst area, karst development level is not high, groundwater circulation is weak, it is difficult to get recharge quickly, so the seepage field recovery of the import section is relatively slow. At the export section karst is developed and groundwater circulate quickly, seepage field rapid recovery.(6) Using numerical simulation method, calculated the water inflow of the section Daao tunnel. With the theoretical calculation formula (such as rainfall infiltration method, analytical method, analogy method, etc.) calculating the tunnel water inflow, obtained the preliminary scope of import and export section of Daao tunnel water inflow. From K97+860to K98+420is117.60～205.07m3/d; From K98+420to K98+765is674.82～846.08m3/d. The research provided the basis for the tunnel’s design and construction. |
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