Analysis of TBM Disc Cutter Damage And Countermeasures

Ⅰ. Reasons for TBM cutter breakage

In different types of TBM and the processes of tunneling with different types of surrounding rock, there are many reasons for the damage of TBM cutters, and mainly caused by the cutter quality, the hardness of the surrounding rock, and the manual operation.

According to the breakage of TBM cutter, correct analysis of its causes will help the TBM operator to operate correctly, avoid cutter breakage caused by human factors, and also help to find problems in time and take corrective measures in time.

II. Wear or damage conditions of TBM disc cutter

1. The cutter ring is evenly worn, which is normal wear. As long as it reaches the general wear size, it can be replaced.

2. One side of the cutter ring is ground off or is ground into a polygon. This is mainly because the bearing of the TBM disc cutter is damaged and cannot rotate normally. Once it is found, it needs to be replaced immediately.

3. The curling edge of the cutter ring is mainly caused by the hard rock and the large driving thrust of the tunnel boring machine. Sometimes it is because the quality of the steel that produces these disc cutters is soft, which can also cause the disc cutter ring to curl up. When this happens, the TBM operator needs to appropriately reduce the driving thrust and driving speed, which can greatly alleviate the severity of the curling edge. In addition, according to the actual situation, the cutter can wait for it to be worn to a certain extent before replacing it without affecting the excavation.

4. The blade of the cutter ring is serrated. Under the circumstance that the surrounding rock is relatively hard, the blade ring of the TBM disc cutter is generally more prone to beating. If the quality of the ring steel is hard and brittle, this phenomenon is also prone to occur when it is cutting rocks. When this occurs with only one or two disc cutters, it is generally due to the TBM operator's too fast advancing speed and too much driving thrust when the cutters are in contact with the surrounding rock at the initial stage of a stroke, which causes the TBM cutter to collide with the surrounding rock， and let the blade of the cutter ring is serrated. In either case, as long as the wear of the cutter ring blade is not too severe and does not affect its ability to cut rock, it can continue to be used without replacement. When the wear of the cutter ring blade is serious, it needs to be replaced as soon as it is found.

5. The cutter hub heats up and leaks oil, mainly because the internal bearing of the TBM cutters has been damaged. As soon as this situation is found, it needs to be replaced immediately.

6. The cutter ring is broken and slipped. When the cutter ring of the TBM disc cutter is broken, the cutter ring cannot cut the rock normally, and it is easy to fall off the rotating shaft, and the driving thrust of the TBM will increase significantly, and the hydraulic and motor systems will be overloaded, which will affect the normal excavation. This is mainly due to poor temperature control during the installation of the cutter ring, too tight installation of the cutter ring, too fast initial tunneling speed of the TBM, and violent collision between the cutter and the surrounding rock. After this happens, the TBM disc cutter needs to be replaced immediately.

7. The sealing ring of the cutter hub falls off. This phenomenon is mainly caused by the improper installation of the TBM disc cutter during assembly and the weak welding of the sealing ring. In addition, this can also occur when the cutter head speed is set too high during TBM tunneling. When seals are found to have fallen off, cutters can refit them inside the cutter head without removing them for repairs. If it is found that the cutter ring has been dislocated or fallen off, it needs to be replaced immediately.

8. Damage to the TBM double disc cutter. In general, it is necessary to replace the rotating bearing due to damage, and it must be replaced as soon as it is found. If the replacement is not timely, a chain reaction is likely to occur, so that multiple double disc cutters will be damaged at the same time, resulting in heavy losses. The gauge cutter is generally subjected to large and uneven instantaneous force due to frequent direction adjustment, and it is easy to wear the cutter into a polygon. This requires the TBM operator to stop the TBM from advancing forward or slow down the driving speed when adjusting the TBM's driving direction, and then adjust the direction, which can effectively reduce the wear of the TBM gage cutters.