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Keywords: tunnel boring machine tool disc hob inspection and maintenance
TBM (Tunnel Boring Machine) is the most effective large-scale machine for long tunnel construction. When drilling, the disc-shaped hob blade mounted on the cutter head is used to wedge the rock into the rock. The cutter rotates to drive the hob to roll on the face. Continuous rock breaking, the cutter head is pushed forward, and the hob breaks the rock to form a hole. The disc hob mounted on the TBM cutter is a proprietary tool of TBM. Its technical performance is one of the key technologies to expand the scope of TBM construction and reduce the construction cost. The famous TBM manufacturers from abroad use the tools. Long-term research has continuously improved the performance of TBM tools to make them competitive. However, the tool performance must be properly used in the construction to fully play. During the construction, the used tools should be strictly tested and repaired in time, so that the tools of the machine can be reliable, reduce the tool failure in the excavation, and improve the utilization rate of the machine, thus improving the driving speed; the correct use of the tool must also include the correct replacement of the tool. And its spare parts, thus reducing tool consumption. Proper use of the tool not only increases the speed of the tunnel but also reduces the tunneling cost from the above two aspects. Especially in hard rock, its importance is more obvious. In the construction of the Qinling Tunnel of Xikang Railway and the TBM construction of the Taohuapu No. 1 Tunnel of the Southwest Railway, on the basis of mastering the introduction technology of digestion, the tool technology in TBM construction was deeply studied, and a set of construction conditions in accordance with China was formed. Strong detection and maintenance technology, and achieved good technical and economic results. The author participated in the tool use and research of these two tunnel constructions. This paper is a summary of the 17" disk hob detection and maintenance technology of the TB880E type roadheader.
Technical requirements for tool preparation for 1TBM construction
A series of tools such as cutter inspection, tool change, and tool maintenance in TBM construction, which are used to make the tools on the cutter head in good condition, are collectively referred to as tool preparation. It is an important part of TBM construction work, and has direct progress on tunnel construction progress and cost. The impact and professionalism are one of the key points of TBM construction technology.
1.1 Improve tool reliability and reduce downtime in the tunneling
During the construction of TBM, the processes such as excavation, slag removal and support can be carried out in parallel and continuously, so that the excavation speed is fast. However, due to factors such as geological factors, machine failures, tool failures, construction management techniques, etc., the machine is shut down for a long time, and the utilization rate of the operation and excavation is not high. In the construction of the Qinling Tunnel of Xikang Railway and the TBM construction of the Taohuapu No. 1 Tunnel of the Southwest Railway, the utilization rate of TBM is only 30%, while that of foreign countries generally reaches 40%, and the highest reaches 60%. Improving the utilization rate of TBM, that is, improving the technical level of TBM construction and reducing the impact of various construction processes on the normal operation of the machine, is the key to reducing the construction cost of TBM construction in China.
During the construction of TBM in the exit of Qinling Tunnel of Xikang Railway, the ratio of downtime to construction time due to tooling is 16.3%, which means that the average construction time of 18h per day (6h for TBM construction and 18h â€‹â€‹for excavation) For nearly 3 hours, the machine was stopped due to the tool. When the hob is broken, it bears huge load and impact, severe friction and high temperature. The surface of each part, especially the tip, is worn, the connection properties of each part are destroyed, the performance of lubricating oil and rubber seal is reduced, and the tool is cut. Gradually lose the ability to break rock, and replace it after using it for a while.
Therefore, the replacement of tools is an important and indispensable task in the construction of TBM, which will inevitably take up part of the construction time. It is reasonable to take the initiative to change the knife as much as possible, that is, to change the tool during the daily construction time. This requires accurate judgment of the tool state, neither blindly changing, increasing tool consumption, but also reducing tool failure for the upcoming tunneling, and trying to reduce tool leakage, knife ring eccentricity, bolt loss or looseness during tunneling. The phenomenon is not allowed, thus reducing the time required for the cutter to check and the tool change during the forced stop. It takes at least two hours to stop and enter the cutterhead for inspection and then replace the knife. This greatly reduces the progress of the TBM. Table 1 lists the tool replacement statistics of three TB880E roadheader construction projects. It can be seen that in the TBM construction of the Qinling tunnel exit and the Taohuapu No. 1 tunnel, the tool change due to the wear of the cutter ring accounts for 80%. It is higher than the 57.2% of the construction of the Qinling tunnel. This shows that the tool state of the latter is relatively poor, and the faults generated by the tools in the tunneling are more, and the impact on the tunneling will be greater.
In order to reduce the tool failure caused by such excavation, the tool quality of the machine must be strictly controlled. By strictly checking the tool outside the hole and carefully repairing it, the tool that is driven into the hole is worn in the cutter ring. Sealing oil leakage, bearing damage, connection and mating failures caused by improper inspection and repair before the limit size account for less than 5% of the total number of inspection and repair tools, which will greatly reduce the passive tool change in the tunneling . Reduce the time for tool change and increase the utilization rate of the machine. This is a high requirement for the TBM construction tool preparation work.
1.2 Reduce tool consumption and reduce tunneling costs
In the construction cost of hard rock roadheader, the tool cost accounts for a large proportion. The harder the stone quality is, the higher the tool cost ratio is. In the hard gneiss area of â€‹â€‹the Qinling tunnel, the tool cost is one-third of the tunneling cost. Reducing tool consumption is the main means to reduce the cost of tunneling and is one of the main tasks of TBM construction tooling. Reduce tool consumption should start from the following aspects.
(1) Correctly use the cutter ring so that the actual wear amount of the cutter ring is not less than 90% of the allowable wear amount. The use of the knife ring is large and expensive. The cost of the knife ring in the TBM construction of the Qinling Tunnel exit accounts for 30% of the tool cost. The allowable wear amount of the positive knife ring in the radial direction is 38 mm, and the edge knife and the center knife cutter ring are 20 mm, which must be fully utilized to reduce the cutter ring consumption.
(2) Reasonable use of bearings to give full play to the service life of bearings. The bearing consumption is large and the price is high. In the TBM construction of the Qinling tunnel exit, the tool bearing cost accounts for 17% of the tool cost. According to Wirth's technical regulations, the service life of the tool bearing is 287.7 hours. After analysis, research and continuous testing and improvement, most of the actual bearing life of Qinling Tunnel Exit and Taohuapu No. 1 Tunnel has reached 900 calculation hours, greatly reducing bearing consumption.
(3) Reasonable use of the seal to give full play to the service life of the seal. The sealing consumption is large and expensive. In the TBM construction of the Qinling tunnel exit, the tool sealing cost accounts for 10% of the tool cost. According to Wirth's technical regulations, a new seal must be replaced each time the tool is disassembled and repaired. After analysis and test, most of the seals were reused during the construction of Qinling Tunnel Exit and Taohuapu No. 1 Tunnel, and some were repaired and used, which greatly reduced the consumption of seals.
(4) Reduce accidental damage to the tool during excavation. Due to the accidental damage of the tool caused by the excessive adjustment of the machine and the uneven geological section, the damaged tools are often not one, but many are generally serious and difficult to repair. Great impact. Operation and construction organization and management must be improved to reduce these accidental damages and losses.
(5) Reduce the consumption of large parts such as the cutter body, the knife cover and the cutter shaft. These large parts are expensive, and they tend to be deformed and worn during use. It is difficult to determine whether they can continue to be used. Correct calibration standards and testing methods must be established, and restorative repairs should be performed by methods such as calibration and brush plating to reduce the consumption of these parts.
2 tool bearing life and seal failure
The knives on the TB880E tunnel boring machine have 6 central knives, 62 positive knives, 3 side knives, and 2 reaming knives. There are 4 kinds of 73 kinds, which are arranged according to certain rules and installed on the cutter head. The structure of the positive hob and the mounting method on the cutter head are shown in Fig. 1. The side knife is basically the same as the front knife. Bearings and seals are two important devices on the tool and have a particularly important impact on the reliability of the tooling operation and tool consumption.
2.1 Bearing life and maintenance
Wirth stipulates that the life of the positive and side cutter bearings is 287.7 hours. The operating hours of the tool at different tool positions are multiplied by the tool position factor. When the calculated hour reaches the value, the bearing is replaced. This lifetime is experimentally tested with 90% reliability. According to the bearing life range shown in Figure 2, 10% of the bearing life is lower than this value, 90% of the bearing life is higher than this value, and the average of all bearing life is 4 times of this value. According to this, the following analysis can be made: 1 Since 10% of the bearing life is lower than this value, 20% of the tools will be damaged by the bearing damage before, and the tool will be 20% unreliable. It is very unfavorable and must be minimized; 290% of the bearing life is greater than this value, and can be used. According to this replacement bearing, a large number of bearings are wasted.
Research suggests that Wirth's approach to bearing timing replacement is not appropriate. Through regular inspection and disintegration inspection, the expected life of the bearing is determined according to the change of the bearing torque value, the change of the lubricating oil, the surface of the rolling element, especially the fatigue damage area of â€‹â€‹the rolling surface of the bearing inner ring, and the inspection and maintenance of the tool ensures The bearings are reliable as expected. During the construction of the Qinling Tunnel Exit and the Taohuapu No. 1 Tunnel, the life of most of the tool bearings reached 900h, which reduced the consumption of the bearings and improved the reliability of the tools.
2.2 Seal failure and maintenance
Wirth stipulates that all used tools must be replaced with new seals during disassembly and repair. The original seals are scrapped and consume a lot. The sealing of the disc hob consists of a metal ring and a rubber ring, which has a test life of up to 5000 h. According to the analysis, the main reason for the failure of the tool seal is the loss of elasticity of the rubber ring and the temperature change. Due to the change of geological conditions and the different working positions, the working temperature of the tool is higher under some conditions, which damages the sealing performance of the rubber ring. Another reason is that there are metal particles in the lubricating oil that damage the sealing surface. Both are accidental.
Use the following methods to repair the seal: 1 The rubber ring must be replaced when disassembling and repairing the assembled tool; 2 If the metal is found to be contained in the lubricating oil or the amount of oil has been reduced when the tool is repaired and disassembled, the metal ring is replaced at the same time; Send professional factory repairs, most of which can be repaired before use. This not only improves the reliability of the tool seal, but also greatly reduces the consumption of the seal.
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