Is the shield machine disposable, and why is the shield machine buried when it runs out

Shield machine. It is not a one-time one, but the external steel structure parts such as the shield tail are discarded when the machine is dismantled after the tunnel penetrates, and other parts can be used repeatedly.

The full name of the shield machine is the shield tunnel boring machine.

It is a special construction machinery for tunnel excavation, modern shield boring machine integrates light, machinery, electricity, hydraulics, sensing, information technology, and has the functions of excavation and cutting soil, conveying ballast, assembling tunnel lining, surveying and guiding deviation correction, etc., involving geology, civil engineering, machinery, mechanics, hydraulics, electrical, control, measurement and other disciplines and technologies, and it is necessary to carry out "tailor-made" design and manufacturing according to different geology, and the reliability requirements are extremely high. The shield boring machine has been widely used in subway, railway, highway, municipal, hydropower and other tunnel projects.

The shield machine depends on its design service life, generally the main bearing 10,000 hours or 15,000 hours, or whether the wear resistance of the cutterhead is suitable for the next project.

The shield machine depends on his design service life, generally the main bearing 10,000 hours or 15,000 hours, there are also special shield machines designed for a certain day tunnel, the tunnel penetrates after dismantling the external steel structure parts such as the shield tail, as long as the more valuable parts, this situation is also a one-time shield machine.

Not a one-time one, one EPB can be used in multiple projects.

Isn't it a bit expensive to say at a time, basically dig a route, and repair it can still be used.

The reason for in-situ burial, the on-site construction conditions are complex, and the lifting construction is difficult, resulting in the cost of lifting and reusing higher than the loss caused by in-situ burial; Shield machine. During the construction process, it has been damaged and aged seriously, and the cost of lifting and repairing it for the next use is greater than the loss caused by choosing to bury it in situ, so it chooses to bury it in situ.

Shield machine. A shield machine is a method that uses a shield.

tunnel boring machines. The shield construction method is the "shield" (referring to the supporting segment) of the tunnel constructed (laid) at the same time as the roadheader is excavating, which is different from the open construction method. Internationally, the wide potato slippery, generalized shield machine can also be used for rock formations, but it is different from the open (non-shield method) tunnel boring machine.

In China, it is customary to call tunnel boring machines used in soft soil formations (narrow) shield machines, and those used in rock formations (narrow) TBM.

As far as the domestic shield project is concerned, the shield machine is expensive, and the shield machine that cannot be fully recovered must be disassembled and recovered from the internal equipment parts of the shield machine

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.

It was first developed by a French engineerBrunet was invented in 1842.

Inspired by the phenomenon of observing maggots drilling holes in the wood of ships and expelling a slime from the body to strengthen the caves, the French engineer Brunel began to study the shield construction in 1818, and in 1825, he used a rectangular shield to build the world's first underwater tunnel (wide and high) under the River Thames in London Mountain, England. It encountered great difficulties in the construction process, and was twice flooded by the river, and it was not completed until 1835, when an improved shield was used, and it was completed in 1843. Later, in 1865, Barlow built a tunnel at the bottom of the Thames with a circular shield with a diameter of one metre.

In 1847, in the construction of the south line of the London Underground Railway City, the British Gretelhead used the pneumatic shield method for the first time in the clay layer and the water-bearing sand layer, and for the first time pressed the grout behind the lining to fill the gap between the shield tail and the lining, creating a relatively complete pneumatic shield construction technology, laying the foundation for the modern shield construction and promoting the development of the shield construction.

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 component acts as a shield, which acts as a temporary support for the excavated unlined tunnel section, bearing the pressure of the surrounding soil layer and sometimes the groundwater pressure and keeping the groundwater out. Excavation, earth drainage, lining and other operations were carried out under the cover of shields.

1. The excavation of the shield machine: the hydraulic motor drives the cutterhead to rotate, and at the same time opens the propulsion cylinder of the shield machine, and pushes the shield machine forward, with the forward advancement of the propulsion cylinder, the cutterhead continues to rotate, and the ballast that is cut down fills the soil silo, at this time, the screw conveyor is started to discharge the cut muck 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 of soil discharge and the speed of soil discharge in the tunneling: when the ballast in the soil bin and the screw conveyor accumulates to a certain amount, the resistance of the muck cut from the excavation face into the soil bin through the knife groove increases, when the earth pressure of the soil bin is balanced with the earth pressure of the excavation face and the water pressure of the groundwater, the excavation face can remain stable, and the ground part corresponding to the excavation face will not collapse or uplift. In this case, as long as the amount of muck conveyed from the screw conveyor and the silo is balanced with the amount of muck in the cut flow silo, the excavation work can proceed smoothly.

3. Segment assembly: After the distance of the shield machine tunneling a ring, the operator of the assembly machine operates the assembly machine to assemble the single-layer lining segment to make the tunnel formed.

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.

Dear, hello, I am glad to answer for you, why the shield machine is a disposable is that the shield machine is a tunnel boring machine that uses the shield method. The construction method of shield is the "shield" (referring to the supporting segment) of the tunnel constructed (laid) by the roadheader at the same time as the tunneling, which is different from the open construction method. Internationally, generalized shield machines can also be used in rock formations, but they are different from open (non-shield) tunnel boring machines.

In China, it is customary to call the tunnel boring machine used for the pure bond of the soft soil stratum (narrow) shield machine, and the one used for rock strata is called (narrow) TBM. The reason for in-situ burial, the on-site construction conditions are complex, and the lifting construction is difficult, resulting in the cost of lifting and reusing higher than the loss caused by in-situ burial; The construction process of the shield pants has been damaged and aged seriously, and the cost of lifting and repairing the next use is greater than the loss caused by the choice of in-situ burial, so the choice of in-situ burial. Those that have reached the end of their life will be buried in it, which is more common abroad.

Most of China will be raised from the receiving well. The cost of a TBM that reaches the mileage is higher than the value of selling scrap. One or two tens of millions of small shields, which are basically disposables, will stagger the main tunnel after penetration, and will be buried after entering.