How to use shield construction?

It was first invented by French engineer M.L. Brunet in 1842.

M.I. Brunel, a French engineer, was inspired by the observation that ship maggots drilled holes in the wood of ships and discharged a kind of mucus from their bodies to reinforce caves. 18 18 began to study shield construction, and in 1825, the world's first underwater tunnel was built with rectangular shield under the Thames in London, England (width 16544). Great difficulties were encountered in the construction process, and it was flooded by the river twice until 1835, and the improved shield was used, which was completed in 1843. Later, P.W. Barlow built a circular shield tunnel with a diameter of 2.2 meters at the bottom of the Thames at 1865.

During the period of 1847, J.H. Greathead of England used pneumatic shield method in clay layer and water-bearing sand layer for the first time, and injected grouting behind the lining for the first time to fill the gap between the shield tail and the lining, creating a relatively complete pneumatic shield method construction technology, laying the foundation for modern shield method construction and promoting the development of shield method construction.

The basic working principle of shield machine is that a cylindrical steel member pushes forward along the tunnel axis to excavate soil. The shell of the barrel assembly is a shield, which plays the role of temporarily supporting the excavated unlined tunnel section and bears the pressure of the surrounding soil layer and sometimes the groundwater pressure to keep the groundwater out. Excavation, spoil, lining and other operations are carried out under the cover of shield.

1. Shield tunneling: the hydraulic motor drives the cutter head to rotate, and at the same time, the shield machine propulsion cylinder is connected to push the shield machine forward. With the propulsion of the propulsion cylinder, the cutter head rotates continuously, and the cut muck fills the mud bin. At this time, the screw conveyor is started, and the cut muck is discharged to the belt conveyor, and then transported to the soil box of the muck truck by the belt conveyor, and then transported to the ground through the shaft.

2. Control the amount and speed of soil discharge during excavation: When the muck in the muck truck and screw conveyor accumulates to a certain amount, the resistance of the muck cut off from the excavation face will increase. When the earth pressure of muck is balanced with the earth pressure of the excavation face and the water pressure of groundwater, the excavation face will remain stable and the corresponding ground part of the excavation face will not collapse or uplift. At this time, as long as the amount of muck transported from the screw conveyor and muck and cut into muck is kept.

3. Segment assembling: After the shield machine has been tunneled for a circle, the assembler operator will operate the assembler to assemble the single-layer lining segment and form the tunnel at one time.