Forecast And Analysis Of The Hydro-geological Structure Characteristic Contributed Water Inflow Of Haidong Tunnel

Haidong tunnel is one of the long length and great depth of the tunnel section of Dali Yunnan water diversion project, located on the east coast of Lake Erhai, tunnel line across a large area of karst region. Since the study area is the site of construction through to complex systems and Qinghai, Tibet, Yunnan, Burma, Indonesia, "Dai" type of structural system, strong tectonic, hydrous rock is cut crushed, the different nature of the aqueous medium penetration combined to form different hydrogeological structure. Tunnel construction will cross different hydrogeological structure, there are differences on the hydrogeological conditions change, prone gushing water disasters. Current tunnel water inflow forecasting, mostly built on the basis of geological boundaries infinite homogeneous medium body above, does not apply to an aqueous medium with a strong heterogeneity and anisotropy of the karst areas. Therefore, this paper studies the hydro-geological structure of the tunnel site,analysis the gushing mode when tunnel through the various hydro-geological structure. In order to cooperate with the actual situation, on the basis of groundwater dynamics method to extend its applicable conditions, thereby improving the accuracy of prediction of water inrush.By combining the study area’s regional geological conditions and hydrogeological conditions, analysing rock permeability characteristics of the tunnel site and features of aqueous medium, master the different combinations of the aqueous medium in the tunnel site, summarizes the tunnel site’s basic hydrogeological structure unit, analysis the change of hydrodynamic conditions and water gushing when it through the different hydrogeological structure unit.Then generalizability tunnel gushing mode and select common groundwater motive law to perfect methods for different tunnel gushing mode, and the following conclusions:(1) Along Haidong tunnel its structure is extremely complex. Changyu village – Dacheng village, the main structural features were EW development, small faults, the line nearly orthogonal crossing the main construction line. Dacheng village- Gaoxing village, is the granite pillar site of Wase fastigiate construction, the fault is not developed. Gaoxing village- the export of water diversion project from Erhai to Binchuan section’s faults are well developed, numerous fault blocks, structural features in the NW-SE oriented, next NE-SW. Fault of various sizes, in structural blocks sedimentary rocks occurrence messy, presence in different directions, and diverse forms of small folds and development, and in each block also has a good integrity intrusions of dyke-like, rock strains-like, the line parallel to the main structure acting through structural blocks in different sizes, the tunnel directly across the fault more than 13;(2) The main types of groundwater include fissure water and karst water, rainfall is the main supply source of groundwater.Negative karst topography and hydraulic conductivity fault are advantages recharge channel of groundwater. Structure play important role to control groundwater occurrence and movement. According to the regional watershed,small river basins and watery structure, the tunnel site area is divided into two one hydrogeologic units, five two hydrogeological units, Yezhu Hill-Wase hydrogeological units(Ⅰ-1) and the Heijiaying hydrogeological units(Ⅱ-3);(3)Tunnel site permeable of aqueous medium divide into strong, medium and weak three grades from the macro. Strong permeability of the aqueous medium includes high degree of development of Permian karst pure limestone(P1), Carboniferous Limestone(C2+3), the Devonian dolomite(D1q) and extensional large scale fault.Followed by medium permeability aqueous medium, including Devonian dolomitic limestone and dolomite(D1k) and medium-scale extensional faults, weak permeability of the aqueous medium include Devonian argillaceous limestone with less development rock(D1l), non-lava rocks, intrusive rocks and pressure faults;(4) Depending on the combination of the aqueous medium tunnel site, combined with rock permeability characteristics, the main tunnel site hydrogeological structure comprises four categories: 1) nearly horizontal uniformity borderless type(Ⅰ); 2) nearly horizontal borderless type(Ⅱ); 3) nearly horizontal uniformity boundary type(Ⅲ), including pressure faults(Ⅲ-1), extensional faults(Ⅲ-2) and intrusive rock(Ⅲ-3) boundary conditions; 4) steep dip stratified boundary type(Ⅳ), according to tunnel through the different permeability of the aqueous medium, can be divided into weak(Ⅳ-2) medium- strong permeability through the aqueous medium(Ⅳ-1) and two sub-permeability category;(5) Tunnel excavation changes groundwater discharge conditions, the tunnel through the different hydrogeological structure tunnel gushing water features generalized into three kinds of modes: 1) homogeneous mode(Ⅰ): while tunnel cross nearly horizontal uniformity borderless type, groundwater movement is borderless; 2) horizontally laminar mode(Ⅱ): while tunnel through the nearly horizontal laminar hydrogeological structure, overlying a relatively impermeable layer or impermeable layer, the underlying having a pressure of groundwater aquifers; 3) vertical laminar mode(Ⅲ): generalized this gushing mode into into Ⅲ-1 andⅢ-2 two subclasses, Ⅲ-1 to tunnel through the strong performance of the aqueous medium permeability, the permeability weak performance of the aqueous medium takes into relatively impermeable layer, Ⅲ-2 to tunnel through the weak permeability of the aqueous medium, the strong penetration into the aqueous medium probability recharge boundary;(6) According to gushing water model of each hydrogeological structure of the tunnel dynamics calculation method is based on to predict groundwater inflow. Selecting steady flow calculation method like Dupuit theory formula, AHКостяковformulas, and Toshiro formula add border limiting condition, and select the appropriate method for calculating confined aquifer, respectively, through the water tunnel hydro-geological structure of each medium water inflow in selecting appropriate calculation methods and parameters, segmentation is calculated under impermeable border control calculation result less than the no boundary condition results, and recharge boundary contrary, the results confined aquifer is less than the results of the unconfined aquifer;(7) Using groundwater dynamics method calculated the overall maximum inflow is 308371 ~ 418321m3/d, tunnel normal water inflow is 26539 ~ 218233m3/d, the formula by adding restrictions on the boundary conditions, the normal water inflow forecast range changed to 12477 ~ 186599m3/d, when performing inflow calculated using groundwater dynamics method, consider the effect of boundary conditions on the tunnel Gushing water hazards, in order to gain more match results more reasonable actual situation.