Groundwater System In The Northern Part Of Huaying Mountain And Its Impact On Tunnel Water Inrush

With the deployment and implementation of China's western development strategy,traffic construction in the western region has become an important part.HuaYing Mountain is located in the northeastern part of Sichuan Basin,and it is a natural moat lies in the west part of Dazhou City.It increases greater difficulties of the communication among Nanchong,Guang'an and Dazhou.So,the way to making a tunnel passing through the northern part of HuaYing Mountain provides the most direct convenience.The strata in the northern part of HuaYing Mountain are dominated by Triassic and Jurassic.In particular,the Triassic in the Luekou slope group and the Lower Jialingjiang Formation are dominated by carbonate rocks.Thus it causes a lot of Karst phenomenon,and leads to more complex and varied groundwater systems in the region.Analysis and summary of the developmental characteristics of karst,distribution characteristics of Karst,etc.,basing on the geological conditions of HuaYing Mountain mother area and the gushing characteristics of HuaYing Mountain tunnel of Nandaliang Exprssway;The main seepage flow and its influence range are analyzed,basing on the hydrogeology and geology;the influence of underground water system on tunnel gushing water,combining with the characteristics of underground water seepage in the north of HuaYing Mountain,all can be seen in this passage.The main conclusions are as follows:(1)In the study area,the hydrological conditions are relatively complex;it has abundant precipitation;also,the regional topography and geomorphology form a good catchment space;tectonic movement leads to stratigraphic fragmentation;and Carbonates provide the basis for karst development.There are many causes,such as structure,lithology,topography and geomorphology and so on,of Karst development.There is also a certain correlation between the various factors.Finally,the favorable conditions for groundwater seepage are provided.(2)The water type of the rock group in the study area can be divided into three types:deep burial karst water,carbonate rock fractured cave water and clastic rock pore fissure water.And the most important is the fractured cave water of carbonate rocks.Among them,the bottom region of Jialing River group and the Xujiahe group is the best water-rich rock group.The sequence combination of different soluble rocks in the study area makes the Karst development different.The large flow of water is mainly located at the bottom of T21 and T1j,forming a concentrated discharge area.(3)The hydrogeological conditions in the study area are complex and the composition of the gushing water is also very complicated.Both of the complexities are mainly caused by the regional precipitation,cave water,underground underground river,clastic rock fissure pore water and other water composition.Surface runoff,fissure water,underground karst cave water,underground river and other water bodies are the direct water source of tunnel water gushing.(4)Through the investigation and data analysis,the factors of tunnel gushing in the study area are determined,including regional precipitation,surface runoff,topography,stratigraphic lithology,geological structure,etc.The sensitivity analysis of tunnel gushing water was carried out by orthogonal method,and the regional precipitation was determined as the most important factor affecting tunnel gushing.(5)The flow-3D fluid simulation software is used to simulate the tunnel excavation before and after excavation and the expected control measures,to determine the change and degree of underground water seepage before and after the tunnel excavation,and to obtain a new discharge datum in the research area.The seepage flow rate and the flow rate of the groundwater are all greatly increased,which leads to the increase of the tunnel water inflow.It is a feasible method to determine the surface plugging in the study area by simulating the seepage of groundwater after the plugging operation on the surface.(6)According to the characteristics of groundwater system in the study area and the characteristics of water gushing in HuaYing Mountain Mountain tunnel,some suggestions on water blocking in tunnel construction are proposed.