Application Of Shields Technique In A City's Subway Construction

The subway has many advantages such as great conveyance ability, high speed, low noise, light pollution, and low energy consumption etc. The main cities gradually form the new modern city's transportation mode with various transportation types in which the subway is regarded as the main transportation tool.Construction based on the shield is popular because of its high-degree safety and mechanization, better work environment, less quantity of earth, quick work progress and low-cost construction etc., especially at the situation of complicated geology, high underground water level and very deep tunnels.One of the key techniques on the shield construction is selection of the shield and its configuration. The selection of the shield type is a all-around work, which should synthetically analyze various factors such as geological and hydrological circumstance, time limit for a project, cost, environmental protection, safety and reliability. Only selecting the right type of the shield and configuring the logical assistant equipment can make the tunnel construction successfully achieve. The emphasis of this paper is focused on the method and steps of selecting the type of shield according to the engineering condition, geological circumstance and progress request of some a subway tunnel zone. Compared with some similar engineering examples, this paper investigates and confirms the type of shield, the type of cutting, the layout of cutting tray, expounds the various work mode of the mud-water shield, and confirms the producer of the shielded machines.After confirming the type and the producer of shielded machines, this paper calculate and check the key parameter of the selected shielded machines to insure that capability of the selected shielded machines can meet the engineering request. This paper also studies the shield construction technique in engineering, and puts forward the solution of many special problem such as the digging of shield in grit, the boosting at curve zone, and the snake form and rolling in the boosting process etc.This paper has the practical value not only to the shield construction in some a city, but also to the similar shield construction.