Study On Characteristics Of Gushing Water In A Tunnel Section Of Chenglan Railway

Tunnel engineering is a complex technical disciplines involving a large number of disciplines,the current construction of the tunnel encountered in the process of geological disasters become increasingly prominent,which gushing water has become a highway,railway and a series of traffic infrastructure construction projects in a very serious geological Disaster problem.A large number of gushing water has been produced during the construction of a Chengdu-Lanzhou railway tunnel in the strong earthquake junction area,which seriously affects the construction progress of the tunnel.In order to study the characteristics of water inflow in a tunnel entrance section of Chengdu-Lanzhou railway,This paper from the Chengdu-Lanzhou railway tunnel in the geological environment condition,firstly research the hydrogeological characteristics of the tunnel entrance section;on this basis,a detailed summary of the characteristics of water inlet section of the tunnel,analyzes the causes of water inlet section tunnel water inflow;finally through the theoretical method and three-dimensional numerical simulation method of inlet section the tunnel is predicted.The main achievements of this paper are as follows:?1?The inlet section of the tunnel generally is high mountain and canyon of the topography,the bedrock strata exposed in the Upper Triassic Xinduqiao strata?T₃x?,Zhuwo strata?T₃zh?,and the Middle Triassic Zagunao strata?T₂z?,the lithology of sandstone,slate and phyllite are not typical karst tunnel.The structural activity of the tunnel site is very strong,and there are many fold structures developed.At the same time,there are five sets of dominant joint fissures.?2?The inlet section of tunnel mainly exposed Quaternary unconsolidated rock pore water and bedrock fissure water and a small amount of karst water,accordingly divided into loose rock aquifer,bedrock fissure aquifer and karst fissure aquifer,and the groundwater mainly comes from atmospheric precipitation and adjacent channel recharge,through strong the permeability of stratum migration,and ultimately to spring,bulk flow to the Minjiang excretion,which divided into region?hydrogeological unit mainly supply and main channel to accept adjacent area II hydrogeological unit precipitation recharge acceptance.According to the results of surface and groundwater chemistry test,the water chemistry type of the study section is HCO₃-Mg type.?3?The distribution of gushing water in the gushing area is different,and it is concentrated in the inner wall of the tunnel.The water flow of the 4#horizontal hole and the main hole is large and the column is gushing.Gushing water is stable.The water diversion of the tunnel is different from that of the tunnel,and the water content is less than that of the 4#horizontal hole in the construction section of the 3#horizontal hole.The water content of the 2^#Gushing water.?4?According to the investigation,the D5K217+500^D5K224+472 tunnel is lower than the water level in the tunnel,and the maximum height difference is 94m.The formation of the rock formation in the tunnel is in the form of a large angle;The proportion of sandstone is higher,the permeability coefficient is relatively good,can become a large mouth ditch water migration medium.Therefore,the stratified medium in the study area formed a good migration channel of groundwater,and the water of the big surname was flooded through the layered permeable medium under the influence of the head..?5?By comparing the lithology ratio and the permeability coefficient obtained from the inversion,the ratio of the sandstone content in the section is 2.995,and the permeability coefficient is determined by the proportion of the sandstone in the whole site.According to the groundwater dynamics method and the atmospheric precipitation infiltration method,the total amount of gushing water in the tunnel inlet section is 24578.21m³/d.Through the numerical simulation,it can be seen that the tunnel excavation breaks the balance of groundwater flow under natural conditions,which makes the groundwater flow channel formed and the groundwater is discharged through the tunnel.The amount of gushing water calculated by numerical simulation is 24516.57m³/d,which is basically consistent with the theoretical calculation method.For the treatment of gushing water recommended to"block the main,blocking the combination of" approach.