Group Classification And Control Parameters Of Shield Construction In The Sand And Gravel Group Of LanZhou Metro

Aimed at solving the problem of gradually deteriorating urban transportation, many countries in the word start to replace the three-dimensional rapid rail mode of transportation by the traditional graphic mode of transportation. At present, the urban rail transportation system that the underground rail transportation coexisting with sorts of rail transportation is dominant is formed in lots of metropolises. Besides, the dominant rail transportation has the quality of less noisy, higher speed, larger transportation capacity, less contaminant and lower energy-consuming. The shield tunnelling method is applied much widely in the construction of the subway and tunnel. However, there are a great many of risk factors in the process of the shield tunneling method, such as the earth surface collapse led by the inappropriate parameters settings of tunneling method and severe wear to shield tool led by inappropriate operation of the Shield. Owing to these risk factors happening frequently, it is the effective controlling and regulating to the process of the shield that can protect the construction from these risk. As a result, the dividing method of the risk of security groups in shielding tunneling considering both the characteristics of shield tunnel surrounding rock and environmental risk condition is significant to controlling risk of security in shielding construction. Group dividing lays foundation for risk controlling in the process of shielding. Only if the theory and method of group dividing are determined appropriately, the controlling scope of main constructive parameters can be given so that it can prevent the risk in the process of shielding.On the basis of a great quality of literature, the paper did analyze shielding constructive tunneling parameters of the sandy cobble stratum in the background of the project of shielding section of subway1line in Lanzhou. The main content folllows:Firstly, sort the geological prospecting data and by sorting and analyzing the report of the geological prospecting and excavation plan and the formation of longitudinal surface chart, it can divide the shielding section as groups on the basis of the formation characteristics of shield tunnel penetration,the relationship between groundwater level and the vertical section of the tunnel, the thickness of earth covering the shielding tunnel, the shield tunnels surrounding environment and its status.Secondly, by citing a great deal of literature, acquiring the impact factors of shielding constructive controlling parameters, the main controlling parameters (soil warehouses pressure, cutter torque, propulsive force and so on) are calculated theoretically.At last, shield construction control parameters are optimized by numerical simulations and theoretical calculations with engineering test.