According to the analysis of Liaocheng Sanli Machinery Company, a drilling tool manufacturer, for shield machines, the cutting system is the cutting cutter head and its driving system. The excavation system has a decisive influence on the construction effect of the shield machine, and the difference of selection also has a great influence on the cost of the shield machine. The selection of the cutter head can affect 4% ~ 8% of the total cost, especially the equipment torque of the excavation equipment is one of the most basic parameters of the shield machine. The cutting cutter head of the shield machine is a disc-shaped cutter that rotates or shakes. It is composed of a cutter for cutting the ground, a panel for stabilizing the cutting surface, an unearthed notch, a driving mechanism for rotating or shaking, and a bearing mechanism.
Influencing Factors of 1. Shield Wear
Under the action of the propulsion force of the shield machine, the shield cutter produces a certain pressure on the soil of the excavation face. With the rotation of the cutter head, the tool and the sand abrasive friction, resulting in wear. The wear of the tool is related to the geological conditions, the material of the shield tool and its installation position on the cutter head, and increases with the increase of the tool excavation mileage. The tool arranged in the periphery of the cutter head is fast worn, easy to break and short life because of its high linear speed and long cutting route. The main form of tool damage is the wear and fall of the tool. The wear of the tool is affected by the material, hardness, thrust, geological conditions and cutting depth, speed and time of the tool. The tool shedding is mainly related to the installation method, and is also affected by the wear of the tool handle and gravel and obstacles during construction. Shield machine in the excavation will encounter a variety of different strata, from silt, clay, sand, gravel layer to soft rock and hard rock. In the process of excavation, the force of the tool is complex and the working environment is bad. The tool wear is closely related to the construction stratum. Muddy clay, silty clay, clayey silt and other strata on the tool wear is very small, and sand, sand gravel gravel strata on the tool wear is very serious, and even make the tool break. This situation has been confirmed in the construction of the project.
Analysis of Shield Tool Wear of Structural Parts of 2. Shield Machine
1. Broken cutter ring
The material and geological lithology of the knife ring are not applicable. When the compressive strength of the rock is high, the hardness of the knife ring itself is also high, and the impact resistance of the knife ring will also decrease, which will cause the knife ring fracture, called impact fatigue fracture. At the same time, when the fit clearance interference exceeds the specified value, the cutter ring will be broken due to the large temperature difference between the inside and outside of the cutter during tunneling, which is called internal stress fracture. In the tunneling process, the tool cooling effect is not good, especially in the silt, clay geology or rock fracture zone interlayer caused by the tool is wrapped, will cause the knife ring fracture, called internal stress fracture.
2. Bearing damage and eccentric wear of the cutter ring
The sealing effect of the engineering tool is poor, including seal fit clearance, rubber elasticity and hardness, mechanical seal flatness, mechanical seal surface hardness and wear resistance, etc. After mud and sand enter the tool and cause bearing damage, the tool ring will produce eccentric wear. The thermal expansion coefficient of grease exceeds the regulations, the sealing grease overflows when the tool is heated, muddy water enters the tool bearing when cooling, or the internal air is not exhausted during assembly, after the bearing is damaged, the cutter ring is eccentric wear; the assembly clearance of the rotating parts of the cutter is unreasonable. When the rotating torque of the cutter ring exceeds the specified value, the bearing will be accelerated and damaged; when the rotating torque is lower than the specified value, the free gap between the seal and the sealing surface will be too large, the seal will fail, and muddy water will enter, causing the cutter ring to wear after the bearing is damaged.