Study On Construction Of Mining Metro Tunnel Under The River In Karst Area

Traffic jams and pollution from vehicle exhaust are getting worse and worse in many cities with the development of economy after 40-year reform and opening-up and fast urbanization in China.For solving the mentioned city problems,More and more cities pay attention to public transportation and regard the metro as the main solution.There is explosive development of metro thus some metro tunnels are tunneled in the complex geological condition.Construction technology about metro tunneling under the river in the karst stratum by mining is discussed based on the Guiyang Urban Rail Transit No.1 and provides technical references for similar projects in the future.In this thesis,construction technology is illustrated from karst theory,curtain grouting and treatment for river,main research contents and conclusions are following:1.The karst development mechanism is demonstrated and the roles of groundwater corrosion and ability of flow,rock solubility and permeability during karst growth are explained.The characteristics of groundwater occurrence and migration in the site are good for groundwater collection and karst development.The regularity of karst development in horizontal layers,inclined rock strata,anticlinal fold and syncline is concluded,and karst geological models are built given groundwater corrosion,location of impermeable layer and degree of joints development.The locations and sizes of karst caves are made a survey and the model of karst development in the layer under the river is built.2.The influence of karst cave on tunnel and layer displacement is analyzed by numberical simulation method.According to the survey data of the revealed of karst caves,the two-dimensional numerical calculation models which the karst caves’ diameters are 1m,3m and 5m,located at vault,side and inverted arch of tunnel respectively when the distances between caves and tunnel are 1mm 2m,3m,4m and 5m are created.The vertical displacement of the land surface,the settlement of the vault,the horizontal displacement of the wall and the uplift of the invertial arch are picked out to analyze and find that the karst caves which the distance from the tunnel is less than 3m exert the tunnel more.During the karst metro tunnel construction,groundwater is a big trouble,so the treatment for the karst emission in front of the tunnel face is put forward,different methods of disposal karst caves located at different parts of tunnel are concluded and the way of grouting on the tunnel support where the seepage is serious is shown.3.Curtain grouting is widely popular during the construction of karst tunnel,which is an effective way to deal with tunnel gushing water and reinforcement of the layers.In this thesis,the original curtain grouting plan is listed firstly and the flow pattern of the slurry is discussed according to the slurry ratio.The grouting pump pressure and finishing pressure,the slurry diffusion radius,the distance between grouting hole,the thickness of sealing batholite,the range of curtain grouting and the grouting sequence is analyzed.With the comparison to the actual grouting parameters,the main technical parameters of curtain grouting for shallow buried karst tunnels are obtained.4.It’s an active waterproofing measure that treating for river during the tunnel construction.Based on the theory of hydraulics,the amount of pipes,pipe flow and orifice flow velocity are checked and analyzed to ensure the reliability of steel pipe drainage.Monitoring and measurement scheme for the tunnel excavation under the river is analyzed simply according to the characteristics of tunnel construction under the river and the surrounding environment.