What is a shield machine and what is the shield machine used for

The shield machine is the main construction machinery in the shield construction. The shield construction method is a construction method of digging tunnels under the ground, which uses a shield machine to excavate underground, and safely carries out tunnel excavation and lining operations in the machine while preventing the collapse of the soft foundation excavation face or keeping the excavation face stable. The construction process needs to first excavate a shaft or foundation pit at one end of a certain section of the tunnel, and the shield machine is hoisted in and installed, and the shield machine starts to excavate from the wall opening of the shaft or foundation pit and advances along the design tunnel line until it reaches the end point of another shaft or tunnel in the tunnel line.

The tunnel construction with the shield machine has the characteristics of high degree of automation, manpower saving, fast construction speed, one-time hole, not affected by the climate, the ground settlement can be controlled during excavation, the impact on the ground building is reduced and the water surface traffic is not affected when the underwater excavation is carried out.

The basic principle of operation of the EPB is that a cylindrical steel component excavates the soil while advancing along the axis of the tunnel. The shell of the cylindrical assembly acts as a shield that acts as a temporary brace for the excavated unlined tunnel section, bearing the pressure of the surrounding soil layer and sometimes the groundwater pressure and keeping it out. Excavation, earth drainage, lining and other operations were carried out under the cover of shields.

The basic working principle is that while the earth is excavated, the cylindrical steel members are pushed forward along the axis of the tunnel. The shell of the cylinder assembly is a shield that temporarily supports the excavated unlined tunnel section, which is subjected to the pressure of the surrounding soil layer and sometimes the pressure of groundwater, keeping the groundwater out. Excavation, dumping, lining and other operations are carried out under the cover of the shield.

1.Shield machine tunneling: The hydraulic motor drives the cutterhead to rotate, and at the same time opens the shield machine drive cylinder to push the shield machine forward.

With the forward drive of the drive cylinder, the cutterhead continues to rotate and load the cut muck into the silo. At this point, the screw conveyor begins to unload the cut muck onto the belt conveyor, which then transports it to the soil box of the muck truck and then conveys it to the surface through the shaft.

2.Control the amount of soil discharge and the speed of soil discharge during excavation: when the ballast in the soil bin and the screw conveyor is accumulated to a certain amount, the resistance of the intercepted muck on the excavation face to enter the soil bin through the knife groove increases.

When the earth pressure of the earth silo is balanced with the earth pressure on the excavation face and the water pressure of the groundwater, the excavation face can remain stable, and the corresponding ground part of the excavation face will not collapse or expand. At this time, as long as the amount of muck transported from the screw conveyor and the silo and the cut-off muck are kept in the silo.

3.Segment assembly: After the shield machine excavates a circle distance, the operator of the assembly machine manually operates the assembly machine to assemble a single layer of lining segments, and the tunnel can be formed at one time.

The function of the EPB is to excavate tunnels, which are divided into earth pressure balance and water pressure balance.

A shield is a type of tunnel boring machine that uses the shield method. (Note: The shield method is a fully mechanized construction method in the construction of the underground excavation method.)

It can be excavated and excavated more simply underground, and it can be understood by doing an example: using the head "cutterhead" all the way to "eat the soil", "chewing" the soil directly into the machine to "digest" and discharge, all the way to dig tunnels underground, mountains and so on.

The principle and characteristics of the shield machine

According to the working principle, the shield machine is generally divided into hand-excavated shield, extrusion shield, semi-mechanical shield (local air pressure, global air pressure), mechanical shield (open-chest cutting shield, pneumatic shield, slurry pressurized shield, earth pressure balance shield, hybrid shield, special-shaped shield).

The tunnel construction with the shield machine has the characteristics of high degree of automation, manpower saving, fast construction speed, one-time hole, not affected by the climate, the ground settlement can be controlled during excavation, the impact on the ground building is reduced and the water surface traffic is not affected when the underwater excavation is carried out.

The name of the shield machine is derived from the construction method of building tunnels, that is, the shield method.

In addition to the shield method, there is also the mining method for the construction of tunnels.

The structural principle of the shield machine, the subway passage originally came from this.

The shield machine is mainly composed of 9 parts, which are the shield body, cutterhead, cutterhead drive, double-chamber airlock, segment assembler, earth-draining mechanism, back-up supporting device, electrical system and auxiliary equipment.

The size and length of the shield machine are not fixed, and it is designed and manufactured according to the actual needs of subway construction.

So far, the world's largest diameter shield machines are the S-317 and S-318 slurry balance shields manufactured by the German company Herrenknecht, with a diameter of meters, and one of the shield machines is digging the Qianjiang tunnel in the Qiantang River.

The first in the world to use a shield machine to drill tunnels was in the United Kingdom.

China has been able to produce shield machines independently, and the technology is mainly based on Japanese shields.

01 In recent years, China's surplus foot rail transit can be described as a rapid development, I have to say, this is due to the development and use of shield machine.

02 The shield machine is a kind of machine that uses the shield method to excavate tunnels, and our regular subway is built with the shield machine.

03 Its principle is to build a shield in the tunnel while digging the tunnel to achieve the role of support, which not only improves the efficiency of tunnel excavation, but also increases its safety.

04 In China, the contribution of the shield hall destroying machine in rail transit is undeniable, and it is precisely with the shield machine that China's rail transit will be so developed.