The Research Of The Large Water Inrush Mechanism Of Feixianguan Tunnel In Yakang Highway

With the rapid development of society and economy in our country,more and more tunnels are needed to be constructed.Tunnel gushing often occurs suddenly during the construction which causes huge losses.Therefore it is of great significance to strengthen the research of tunnel water gushing.Large tunnel gushing often occurs in the karst area and the amount of water gushing in the red layer area is small.However,when the large tunnel gushing occurs in the red layer of Feixianguan tunnel in Yakang highway,water inflow reaches to 150 thousand m3/d,which is very rare.Because the study of red layer tunnel barely exists,especially on the red layer tunnel of large water gushing amount,and its geological conditions of syncline structure is typical,The study of Feixianguan tunnel can fill the blank for this project.First of all,water temperature,water chemistry analysis and cluster analysis method are used to analyses the relationship between surface water and tunnel gushing water.Then the method of hydrochemical tracer are adopted to conduct water chemical correlation analysis of heavy metals about gushing water,surface rivers,typical spring point of each hydrogeological unit.And the result is that the tunnel inflow and river surface has a high correlation,tunnel gushing and surface river has the same heavy metal ions.Therefore the hydraulic connection exists between the tunnel inflow and surface river.Through theoretical analysis,the tunnel gushing is mainly supplied through the interlayer of the strong permeable layer,and the supply sources for the flow are Shiyang and Yingjing river,existing the percolation model of the axial and bedding axis.The instantaneous high pressure at the beginning of the gushing water of the tunnel is caused by the high side of the Shiyang river.In order to verify the analysis results of tunnel water gushing and the hydrogeological characteristics along two flow modes,The physical simulation experiments of two kinds of water inrush patterns are carried out to study the source and mechanism of tunnel water inrush.In the physical simulation experiment,various possible situations of tunnel gushing are simulated to discuss the characteristics of tunnel water gushing,whcih is also based on study of the correlation between the attenuation equation of water inflow in each test group and the attenuation equation of actual water inflow in the tunnel.In this paper,the origin and mechanism of water inrush from Feixianguan tunnel are studied,The main conclusions are as follows:(1)According to the analysis of water temperature,water chemistry and system cluster analysis,the main stream of the tunnel gushing from the surface river is determined.(2)In the study area,the geological structure is complex causing a large number of cracks and gaps,forming the complex multi-layer(sandstone)fissure water storage and water network.(3)The physical simulation test is in good agreement with the actual geological body.The geological body is truly reproduced and simulated.Both the process of the physical simulation test and the data is true and reliable.(4)There are two kinds of water inrush patterns in the process of water gushing in the Feixianguan tunnel,such as the bedding axis and the unanimous axis.Interlayer shear zone is also existed.(5)The water flows discharge through the interlayer dislocation zone to the tunne which is the main route for the tunnel gushing.There is a dominant channel in the tunnel gushing,and there is a hydraulic connection with the surface river.(6)The main source of water gushing in the initial stage of water gushing in the Feixianguan tunnel is from the underground water.But with the discharge of the static reserves,the water gushing in the tunnel gradually takes the surface river as the main source.The main water source is Yingjing river,Shiyang river is the second one.(7)The initial high pressure is from the high side of the river,the tunnel gushing suddenly generates when tunnel construction occurs to reveal the backbone network the backbone network bedrock,which causes pressure of the water in the rock.The water quantity of the NW wing of the syncline is infiltrated in the form of an inverted siphon,which leads to the phenomenon of instantaneous high pressure.(8)In the red bed area,there is a large amount of water inrush under some special and complicated geological conditions,which is not a traditional red area and a poor water area.The red layer tunnel gushing water also has its own characteristics,which is significantly different from the traditional large karst water gushing tunnel.