| Gaojiawan tunnel located in Nanjiang County of Bazhong City. It is an important control project in Taoyuan, Sichuan, Shaanxi Province to Bazhong Expressway. The tunnel across the valley right side of the mountain. The tunnel length is about 3996m and the maximum depth is about 627m. It crossing through syncline-anticline-anticline-anticline, all of these structures are oblique folds. The area's geological structure are complex. The geological and hydrogeological conditions of the tunnel site are very complicated, and the most important engineering geological problem is the harm of karst water gushing.In this paper, by means of a large number of geological survey, drilling, geophysical exploration, hydrological test and other engineering means, the development rule and control factors of the tunnel karst, the characteristics and laws of groundwater development are revealed.The controlling factors of Karst tunnel site area: stratigraphic lithology, topography,geological structure, neotectonic movement and so on. The laws of Karst tunnel site area are:positive level, and bedding, and non-uniformity of the deep and vertical zonation , and so on.Hydrodynamic vertical Karst can be divided into: epi-Karst zone, vadose zone, the season alternating with shallow satuiated zone, the pressure of saturated zone and deep water flow with ease; Karst hydrodynamic level can be divided into: recharge areas,recharge of runoff areas and discharge areas.According to the tunnel site characteristics of groundwater systems, we can predict water yield of the tunnel by groundwater runoff modulus method,and judge that the tunnel in Karst area may appears of large water oozing. The result is 3440.70m3/d,4397.13m3/d,1687.08m3/d, 4687.21m3/d and 2155.55m3/d using groundwater runoff modules method,infiltration of precipitation method, a general algorithm for calculating the amount of groundwater, spring flow summation method and groundwater dynamics method, the tunnel is predicted by subsection with the method of groundwater dynamics. The groundwater dynamic method and general algorithm for calculating the amount of groundwater are adopted to predict the water yield of tunnel. The rainfall infiltration and groundwater runoff modulus method and spring flow summation method to predict tunnel water inflow effect.The prediction result coincides with the actual situation of tunnel construction. To evaluate the impacts and hazards of tunnel water leakage on engineering, environment and prediction.According to the engineering hydrogeological conditions of the tunnel site, the paper puts forward the prevention measures of the tunnel water gushing. The influence of tunnel penetration on the hydrological environment of tunnel site is evaluated. This paper puts forward the measures and suggestions for the main water gushing section of tunnel, which is blocking, leading water blocking, and limited drainage. The tunnel has taken to limit emissions of groundwater and the lining of the surrounding rock, the good recovery of the groundwater system, both to ensure the project construction, and reasonable to restore the ecological environment, effectively curb the depletion of water resources. |
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