| Proposed ChengLan railway line construction area has extremely complex stratigraphic rock formation,geological tectonic development and regional tectonic evolution,active tectonic changes and frequent seismicity.The whole line project area terrain ups and downs,the railway has more long tunnel,engineering geological conditions are extremely complex,along the way there are Sinian,Carboniferous,Permian,Triassic carbonate strata,and many deep tunnels.The problem of water inrush in deep tunnel is the main engineering hydrogeological problem affecting the tunnel project in this area,which plays an important role in the railway route scheme.In view of this,it is very necessary to carry out the forecasting of the sudden drop of the Longmenshan tunnel in the Chenglan Railway,which is of great practical significance.Based on the field survey data and the preliminary data collation,the hydrogeological conditions and karst development characteristics of the experimental section are analyzed,and the water bursting condition of the 1 # inclined well of Longmenshan tunnel and 1 # inclined well of Longmenshan tunnel is analyzed.This paper explores the geologic model,occurrence condition and influencing factors of flooding water in the test section,and uses the atmospheric rainfall infiltration coefficient method,the underground runoff modulus method,the groundwater dynamics method and the three-dimensional numerical simulation method to predict the tunnel surge water volume,And the accuracy and suitability of each forecasting method are analyzed by comparing the water volume of the tunnel and the actual surge water.The main research results of the paper are as follows:(1)The study area is a deep-cut alpine gorge landscape with abundant rainfall.In the area,the interbedding of the soluble rock and the non-dissolvable rock is mainly developed.The main development of the large basement is Dawuji inverted complex anticline,Gaochuanping inverted diagonal,the Gaochuanping fault,the Guangtongba fault and the joint fissure development.The area is rich in loose accumulation layer pore water,bedrock fissure water,structural fissure water,carbonate fractured cave water.The mineralization degree of regional water samples is low and the mineralization degree is 0.1 ~ 0.3g / L.The regional hydrogeological zoning can be divided into the Gauchuan River Basin and the Jinshigou Watershed.Through calculation,it can be seen that the two watersheds are not balanced and there is water supply from outside of the River Basin.The karst in the area is relatively developed,mainly in the dissolution fracture,the main hole,the outlet spring point is relatively small.(2)Through the analysis of the geological and hydrogeological conditions of the inclined section of the test section,we know the reason for water outburst at Longan Mountain Tunnel 3# inclined shaft surface(XJ3K1+485)is tunnel construction expose the rich water-rich dolomite formation;the reason for water outburst at Longan Mountain Tunnel 1# inclined shaft surface(XJ3K1+485)is the excavation of permeable rock and insoluble rock contact belt.There are water-rich areas near the contact belt,and the fractured dense zone is developed in the contact zone.The water storage in the rich water area emerges through the joint fissure.The reason for the water bursting in the 1 # inclined shaft of the Longmenshan tunnel is that the tunnel excavation exposes the karst water-rich strata.The upper reaches of the Inclined Shaft are entering the inclined well through karst fissures.(3)Through the analysis of the characteristics of the dipping water in the test section and its corresponding hydrogeological characteristics,we know that the water outburst mode for Longan Mountain Tunnel 3# inclined shaft surface(XJ3K0+396)is hydraulic splitting type and compound water inrush mode;the water outburst mode for Longan Mountain Tunnel 3# inclined shaft surface(XJ3K1+485)is construction to expose water-filled karst pipeline network type.the water outburst mode for Longan Mountain Tunnel 1# inclined shaft is construction to expose water-filled karst pipeline network type.(4)Calculation of water bursting in 3# inclined shaft of Longmenshan tunnel.Based on the deep analysis of the geological conditions and the characteristics of groundwater circulation in the 3# inclined well of Longmenshan tunnel,the water infiltration coefficient method,groundwater runoff modulus method,groundwater dynamic method and three-dimensional numerical simulation method are used to calculate the water inflow.The results show that the steady gushing water and the maximum gushing rate are consistent.The maximum amount of steady gushing water and maximum gushing water are concentrated in the range of XJ3K0~XJ3K0+320(Zbq),XJ3K1+096~XJ3K2+30(D2gn).The minimum amount of steady gushing water and maximum gushing water are concentrated in the range of XJ3K0+634~ XJ3K1+96(S1ln,S2-3mx2).(5)Calculation of water bursting in 1# Inclined shaft of Longmenshan tunnel.Based on the deep analysis of the geological conditions and the characteristics of groundwater circulation in the 1# inclined well of Longmenshan tunnel,the water infiltration coefficient method,groundwater runoff modulus method,groundwater dynamic method are used to calculate the water inflow.The results show that in addition to groundwater dynamic method,the steady gushing water and the maximum gushing rate are consistent.in addition to groundwater dynamic method,the maximum amount of steady gushing water and the maximum gushing water are in the range of XJ3K0+630~XJ3K0+730(P1).The minimum amount of steady gushing water and maximum gushing water are concentrated in the range of XJ3K0+00~XJ3K0+630(C1zn、D3tn).(6)In terms of the accuracy of water bursting prediction,the infiltration coefficient method predicts the highest accuracy of water bursting in No.1 flooding points of Longmenshan tunnel 3# inclined shaft,the groundwater dynamics method predicts the highest accuracy of water bursting in No.3 flooding points,the numerical simulation method predicts the relative accuracy of the water inflow at the No.2,4,5 and 6 flooding points.the infiltration coefficient method predicts the highest accuracy of water bursting in No.10 flooding points of Longmenshan tunnel 1# inclined shaft,the groundwater runoff modulus method predicts the highest accuracy of water bursting in No.1,2,3,4,5,8,9,11 and 12 flooding points,the groundwater dynamics method predicts the highest accuracy of water bursting in No.6,7 flooding points.In general,the prediction accuracy of 1# inclined well in Longmenshan tunnel is obviously higher than that of Longmenshan tunnel 3# inclined well.(7)Suitability analysis method for calculating water bursting in Karst tunnel.In this paper,the rainfall infiltration coefficient method is not applicable to the two test sections for the water bursting prediction in Longemen Mountain 3# inclined well and Longmenshan 1# inclined well.Groundwater runoff modulus method is more suitable for Longmenshan 1# inclined well;The applicability of groundwater dynamics to the two test sections is general;The numerical simulation method has high applicability to Longshan Mountain 3 # inclined well. |
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