The full name of shield machine is shield tunnel boring machine, which is a special construction machinery for tunnel excavation. Modern shield tunneling machine integrates optics, mechanics, electricity, hydraulics, sensing and information technology, and has the functions of digging and cutting soil, conveying soil ballast, assembling tunnel lining, surveying and guiding rectification. , involving geology, civil engineering, machinery, mechanics, hydraulics, electricity, control and measurement, etc. Shield machine has been widely used in subway, railway, highway, municipal, hydropower and other tunnel projects. Shield machine is used in this section of tunnel construction, which has the characteristics of high automation, labor saving, fast construction speed, one-time hole formation, no influence of climate, controllable ground settlement during excavation, little influence on ground buildings, and no influence on water traffic during underwater excavation. In the case of long tunnel line and large buried depth, shield machine construction is more economical and reasonable. The basic working principle of shield machine is that a cylindrical steel member advances along the tunnel axis to dig out the 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. It is understood that the excavation volume of shield construction accounts for 45% of the total subway construction in Beijing. At present, there are 17 shield machines working for subway construction. Although the cost of shield machine is high, it can improve the efficiency of subway underground excavation by 8 to 10 times, and in the process of construction, there is no need for large-scale demolition on the ground, no traffic jam, no noise during construction, no ground subsidence and no impact on the normal life of residents. However, the large shield machine has high added value and complicated manufacturing process, and only a few enterprises in Europe, America and Japan can develop and produce it internationally. Shield machine has a history of nearly 180 years since it came out. It started in Britain and developed in Japan and Germany. In recent 30 years, through the exploration and research on key technologies of EPB and slurry shield, such as effectively sealing the shield machine, ensuring the stability of the excavation surface, controlling the surface uplift and collapse within the specified range, replacing the service life under sealed conditions, and solving some adverse geological conditions such as high water pressure, the shield machine has developed rapidly. Due to the rapid development of Japanese economy and the needs of practical engineering, shield machines, especially EPB and slurry shield machines, have developed rapidly. German shield machine technology is also unique, especially in the process of underground construction, when the air pressure is as high as 0.3MPa, the premise of sealing and replacing the cutter head is guaranteed, thus improving the first tunneling length of the shield machine. Germany has also developed the replacement of worn bits from the atmospheric space inside the large-diameter bits under sealed conditions. The selection principle of shield machine is to adjust measures to local conditions, try to improve the degree of mechanization and reduce the impact on the environment. The shield machine involved in Shenyang Metro is called Pioneer, with a total length of 64.7 meters, a shield part of 9.08 meters, a weight of 420 tons, and a working error of no more than a few millimeters. Price: Germany imported shield machines need about 50 million, Japan imported shield machines need about 30 million or more, and the price of domestic shield machines is generally around 25 million. At present, the shield machine with independent intellectual property rights in China is the domestic "863" series shield machine developed by Shanghai Tunnel Engineering Co., Ltd. In July, 2007, Geng, the chairman of northern heavy industries Group, formally signed an equity transfer agreement with the original shareholders of French NFM Company, and successfully concluded the two-year merger and acquisition negotiations with absolute control, which enabled northern heavy industries to have the most advanced core technology and well-known brands of full range of tunnel shield machines in the world. According to the working principle, shield machines are generally divided into hand-dug shield, extrusion shield, semi-mechanical shield (local air pressure and global air pressure) and mechanical shield (open-chest cutting shield, air pressure shield, slurry pressure shield, earth pressure balance shield, hybrid shield and special-shaped shield). Mud shield machine stabilizes the excavation face by pressurizing mud or mud (usually bentonite suspension). There is a sealed partition behind its cutter head, which forms a mud chamber with the excavation surface and is filled with mud. The mixture of excavated soil and mud is transported to the separation plant outside the hole by mud pump, and the separated mud is reused. Earth pressure balance shield machine takes soil material (adding foam to improve soil if necessary) as the medium to stabilize the excavation face, and forms a soil chamber between the rear partition of the cutter head and the excavation face. The cutter head rotates to dig to increase the soil material, and then the screw feeder rotates to transport the soil material out. The earth pressure in the soil chamber can be adjusted by the rotating excavation speed of the cutter head and the excavation amount (rotation speed) of the screw feeder. According to the classification of shield machines, shield tunneling methods can be divided into: open excavation, mechanical cutting, grid format and extrusion. In order to reduce the disturbance of shield construction to the stratum, jack can be used to drive the shield to make its incision penetrate into the soil layer, and then the soil can be excavated and transported in the incision. Open-cut hand-dug shield and semi-mechanical shield are semi-open-cut, which are suitable for situations where the geological conditions are good and the excavation surface can remain stable or there are auxiliary measures to maintain stability. Generally, the excavation starts from the top and digs down layer by layer. If the soil layer is poor, you can also borrow jacks and bracing plates to temporarily support the excavation face. Open excavation is adopted, which is convenient to deal with isolated obstacles, rectification and overbreak in other ways. In order to minimize the disturbance to the formation, it is necessary to properly control the overbreak and exposure time. Mechanical cutting refers to the excavation method of full-face rotary cutter head with a diameter similar to that of shield. According to geological conditions, broadsword heads can be divided into two types: no sealing plate between tool holders and sealing plate. No sealing plate between tool holders is suitable for conditions with good soil quality. The broadsword excavation method is not as convenient as open excavation in curve construction or rectification. In addition, it is better to clear the obstacles than to dig them openly. The shield with big sword head has complex mechanical structure and high power consumption. At present, advanced slurry pressure shield and earth pressure balance shield at home and abroad all adopt this excavation method. The excavation adopts grid format, and the excavation surface is divided into many grids by grid beams and grids. The supporting function of excavation face is produced by the cohesion of soil and the resistance within the range of grid thickness. When the shield advances, the soil is squeezed out of the grid. Adjust the opening area of the grid according to the nature of the soil. When using grid excavation, after all jacks are retracted, the shield will retreat greatly, resulting in surface subsidence. Therefore, effective measures must be taken to prevent the shield from retreating during construction. Extrusion full extrusion excavation and partial extrusion excavation, because they are not unearthed or only partially unearthed, have great disturbance to the stratum. When building the axis, try to avoid the ground buildings. During local extrusion construction, the excavation amount should be carefully controlled to reduce and control the surface deformation. In full extrusion construction, the shield compacts the soil in a certain range. Edit the market demand and characteristics of shield machine in this section. At present, China has become the largest shield machine market in the world, and the shield machine market in China is in great demand. According to experts' prediction, with the development of urban rail transit in China, the potential market of various shield machines will have an output value of more than 20 billion yuan in the future. China shield machine market has the following characteristics: 1. The climax of subway construction is coming. In China, at present, 23 cities have started to build subways, and 33 cities have been approved by the State Council. Domestic subway shield machine radiates from the central city to the periphery, and will enter the climax of subway development in 20 15 years. 2. The scope is constantly expanding. The application scope of shield machine is developing from urban rail transit to municipal underground pipelines, including sewage pipelines, power pipelines, water supply and drainage pipelines, gas pipelines, urban ditches and so on. 3. Diversification of shield machines. From a single subway shield to a variety, including earth pressure balance shield, slurry shield, open shield, and other special-shaped (double circle, triple circle, rectangle, horseshoe, etc. ) shield. 4. Develop from domestic market to international market. The application of shield machine in tunnel construction has the characteristics of high automation, labor saving, fast construction speed, one-time hole formation, no influence of climate, controllable ground settlement during excavation, little influence on ground buildings, and no influence on water traffic during underwater excavation. Shield machine construction is more economical and reasonable in the case of long tunnel line and large buried depth. The basic working principle of shield machine is that a cylindrical steel member advances along the tunnel axis to dig out the 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. It is understood that the excavation volume of shield construction accounts for 45% of the total subway construction in Beijing. At present, there are 17 shield machines working for subway construction. Although the cost of shield machine is high, it can improve the efficiency of subway underground excavation by 8 to 10 times, and in the process of construction, there is no need for large-scale demolition on the ground, no traffic jam, no noise during construction, no ground subsidence and no impact on the normal life of residents. However, the large shield machine has high added value and complicated manufacturing process, and only a few enterprises in Europe, America and Japan can develop and produce it internationally. Shield machine has a history of nearly 180 years since it came out. It started in Britain and developed in Japan and Germany. In recent 30 years, through the exploration and research on key technologies of EPB and slurry shield, such as effectively sealing the shield machine, ensuring the stability of the excavation surface, controlling the surface uplift and collapse within the specified range, replacing the service life under sealed conditions, and solving some adverse geological conditions such as high water pressure, the shield machine has developed rapidly. Due to the rapid development of Japanese economy and the needs of practical engineering, shield machines, especially EPB and slurry shield machines, have developed rapidly. German shield machine technology is also unique, especially in the process of underground construction, when the air pressure is as high as 0.3MPa, the premise of sealing and replacing the cutter head is guaranteed, thus improving the first tunneling length of the shield machine. Germany has also developed the replacement of worn bits from the atmospheric space inside the large-diameter bits under sealed conditions. The selection principle of shield machine is to adjust measures to local conditions, try to improve the degree of mechanization and reduce the impact on the environment. The shield machine involved in Shenyang Metro is called Pioneer, with a total length of 64.7 meters, a shield part of 9.08 meters, a weight of 420 tons, and a working error of no more than a few millimeters. Price: Germany imported shield machines need about 50 million, Japan imported shield machines need about 30 million or more, and the price of domestic shield machines is generally around 25 million. At present, the shield machine with independent intellectual property rights in China is the domestic "863" series shield machine developed by Shanghai Tunnel Engineering Co., Ltd. In July, 2007, Geng, the chairman of northern heavy industries Group, formally signed an equity transfer agreement with the original shareholders of French NFM Company, and successfully concluded the two-year merger and acquisition negotiations with absolute control, which enabled northern heavy industries to have the most advanced core technology and well-known brands of full range of tunnel shield machines in the world. According to the working principle, shield machines are generally divided into hand-dug shield, extrusion shield, semi-mechanical shield (local air pressure and global air pressure) and mechanical shield (open-chest cutting shield, air pressure shield, slurry pressure shield, earth pressure balance shield, hybrid shield and special-shaped shield). Mud shield machine stabilizes the excavation face by pressurizing mud or mud (usually bentonite suspension). There is a sealed partition behind its cutter head, which forms a mud chamber with the excavation surface and is filled with mud. The mixture of excavated soil and mud is transported to the separation plant outside the hole by mud pump, and the separated mud is reused. Earth pressure balance shield machine takes soil material (adding foam to improve soil if necessary) as the medium to stabilize the excavation face, and forms a soil chamber between the rear partition of the cutter head and the excavation face. The cutter head rotates to dig to increase the soil material, and then the screw feeder rotates to transport the soil material out. The earth pressure in the soil chamber can be adjusted by the rotating excavation speed of the cutter head and the excavation amount (rotation speed) of the screw feeder. According to the classification of shield machines, shield tunneling methods can be divided into: open excavation, mechanical cutting, grid format and extrusion. In order to reduce the disturbance of shield construction to the stratum, jack can be used to drive the shield to make its incision penetrate into the soil layer, and then the soil can be excavated and transported in the incision. Open-cut hand-dug shield and semi-mechanical shield are semi-open-cut, which are suitable for situations where the geological conditions are good and the excavation surface can remain stable or there are auxiliary measures to maintain stability. Generally, the excavation starts from the top and digs down layer by layer. If the soil layer is poor, you can also borrow jacks and bracing plates to temporarily support the excavation face. Open excavation is adopted, which is convenient to deal with isolated obstacles, rectification and overbreak in other ways. In order to minimize the disturbance to the formation, it is necessary to properly control the overbreak and exposure time. Mechanical cutting refers to the excavation method of full-face rotary cutter head with a diameter similar to that of shield. According to geological conditions, broadsword heads can be divided into two types: no sealing plate between tool holders and sealing plate. No sealing plate between tool holders is suitable for conditions with good soil quality. The broadsword excavation method is not as convenient as open excavation in curve construction or rectification. In addition, it is better to clear the obstacles than to dig them openly. The shield with big sword head has complex mechanical structure and high power consumption. At present, advanced slurry pressure shield and earth pressure balance shield at home and abroad all adopt this excavation method. The excavation adopts grid format, and the excavation surface is divided into many grids by grid beams and grids. The supporting function of excavation face is produced by the cohesion of soil and the resistance within the range of grid thickness. When the shield advances, the soil is squeezed out of the grid. Adjust the opening area of the grid according to the nature of the soil. When using grid excavation, after all jacks are retracted, the shield will retreat greatly, resulting in surface subsidence. Therefore, effective measures must be taken to prevent the shield from retreating during construction. Extrusion full extrusion excavation and partial extrusion excavation, because they are not unearthed or only partially unearthed, have great disturbance to the stratum. When building the axis, try to avoid the ground buildings. During local extrusion construction, the excavation amount should be carefully controlled to reduce and control the surface deformation. In full extrusion construction, the shield compacts the soil in a certain range. Edit the market demand and characteristics of shield machine in this section. At present, China has become the largest shield machine market in the world, and the shield machine market in China is in great demand. According to experts' prediction, with the development of urban rail transit in China, the potential market of various shield machines will have an output value of more than 20 billion yuan in the future. China shield machine market has the following characteristics: 1. The climax of subway construction is coming. In China, at present, 23 cities have started to build subways, and 33 cities have been approved by the State Council. Domestic subway shield machine radiates from the central city to the periphery, and will enter the climax of subway development in 20 15 years. 2. The scope is constantly expanding. The application scope of shield machine is developing from urban rail transit to municipal underground pipelines, including sewage pipelines, power pipelines, water supply and drainage pipelines, gas pipelines, urban ditches and so on. 3. Diversification of shield machines. From a single subway shield to a variety, including earth pressure balance shield, slurry shield, open shield, and other special-shaped (double circle, triple circle, rectangle, horseshoe, etc. ) shield. 4. Develop from domestic market to international market. What is the working principle of shield machine? The working principle of shield machine is 1. The hydraulic motor of shield machine drives the cutter head to rotate, and at the same time, it pushes the shield machine forward by opening the propulsion cylinder. As the propulsion cylinder moves forward, 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 vertical shaft. 2. Control the amount and speed of spoil during excavation. When the muck in the muck truck and screw conveyor accumulates to a certain amount, the resistance of the muck cut from the excavation face to the muck increases. 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 can 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 the amount of muck cut into muck are kept. 3. After segment assembling is completed, the operator of the assembling machine operates the assembling machine to assemble the single-layer lining segment, and the tunnel is formed at one time. The composition of shield machine and the function of each component in construction. The maximum diameter of the shield machine is 6.28m, and the total length is 65m, of which the length of the shield machine is 8.5m, the length of the rear supporting equipment is 56.5m, the total weight is about 406t, the total power is configured 1577kW, and the maximum driving torque is 5300kN? M, the maximum propulsion is 36400kN, and the minimum driving speed in Shaanxi can reach 8 cm/min. The shield machine is mainly composed of nine parts: shield body, cutter head drive, double-chamber air brake, segment assembling machine, soil removal mechanism, rear support device, electrical system and auxiliary equipment. 1. The shield is mainly composed of three parts: front shield, middle shield and tail shield. These three parts are tubular, with an outer diameter of 6.25m m. The front protective cover and the pressure-bearing partition welded with it are used to support the cutter head drive and isolate the soil bin from the working space behind it. The pressure of the thrust cylinder can act on the excavation face through the pressure-bearing diaphragm to support and stabilize the excavation face. Five earth pressure sensors are installed at different heights of the pressure-bearing partition, which can be used to detect the earth pressure at different heights in the soil bin. Behind the front shield is the middle shield. The middle shield and the front shield are connected by bolts through flanges. There are 30 propulsion cylinders at the periphery of the inner side of the intermediate shield. The plastic protective cover is installed on the rod of the propulsion cylinder to push the fan-shaped block installed at the back. By controlling the rod of the hydraulic cylinder to extend backward, it can provide forward driving force for the shield machine. These 30 jacks are divided into four groups: A, B, C and D according to up, down, left and right. During driving, there can be more belts in the operating room. Behind the middle shield is a tail shield, which is connected with the middle shield through a 14 passive following articulated cylinder. This hinge connection can make the shield machine easy to turn. 2. Cutter head Cutter head is a kind of cutter head with multiple feed slots, which is located at the front end of shield machine and used for cutting soil. The opening rate of cutter head is about 28%, and the diameter of cutter head is 6.28 m, which is also the largest part of shield machine. The flange with four supporting banners is used to connect the cutter head and the cutter head driving part. According to the hardness of the cut soil, hard rock or soft soil can be installed on the cutter head, and a cutter head can also be installed on the outside. The piston rod stroke of the overbreak tool is 50 mm, and all models installed on the cutter head are connected by bolts, which can be replaced from the mud bin behind the cutter head. A rotary joint is installed at the rear of the flange, which is used to input foam or bentonite to the cutter head panel and deliver hydraulic oil to the hydraulic cylinder of the overbreak cutter. 3. Cutter head drive The cutter head drive is firmly connected with the flange on the pressure-bearing partition of the front cover through bolts, which can make the cutter head realize stepless speed change clockwise and counterclockwise by 0-6. 1 rpm. Cutter head drive is mainly composed of eight groups of transmission pairs and main gear box. Each set of transmission pairs consists of an inclined shaft variable axial plunger motor and a water-cooled variable speed gearbox. A group of transmission pairs have a braking device in the variable speed gearbox for braking the cutter head. The quantitative spiral hydraulic pump installed on the pressure-bearing partition on the right side of the front cover drives the gear oil in the main gearbox to lubricate the main gearbox, and the water-cooled gear oil cooler in the oil circuit is used to cool the gear oil. 4. Double-chamber airlock The double-chamber airlock is installed on the front cover, including the front chamber and the main chamber. When worn workers enter the earth warehouse for inspection and replacement during excavation, a double-chamber air brake should be used. When entering the mud bin, in order to avoid the collapse of the excavation surface, it is necessary to establish and maintain an air pressure in the mud bin that is suitable for the earth pressure and water pressure in the deep stratum, so that when workers want to enter and leave the mud bin, there is a problem of adapting to the pressure in the mud bin. By adjusting the pressure in the front chamber and the main chamber of the air lock, the workers can adapt to the change between the normal pressure and the pressure in the excavation bin. However, it should be noted that only qualified personnel who have passed the high-pressure gas inspection and received corresponding training can enter and leave the pressurized mud bin through the air lock. Now, the function of the double-chamber air lock is illustrated by taking the example of workers entering the pressurized mud bin from the atmospheric working environment. Staff A first enters the main room from the front room, closes the isolation door between the front room and the main room, pressurizes the main room according to the prescribed procedures until the pressure of the main room is the same as that of the earth bin, opens the gate valve between the main room and the earth bin to balance the pressure between them, and then opens the isolation between the main room and the earth bin.