Classification and application of shield cutting tools

Tool shape and its function

The shape of the cutting tool must adapt to the characteristics of construction geology, and its functions and requirements are different at different positions of the cutting section. Therefore, the cutting tool should be designed.

① The cutting efficiency of cutting tool in sand and gravel stratum, that is, how to reduce cutting resistance and ensure the fluidity of cutting soil.

② By changing the shape of the cutter, the cutting wear can be reduced and the durability of the cutter can be improved.

③ To meet the needs of construction in prosperous urban areas, minimize the interference of the soil cutting process of the cutter head rotating cutter to the surrounding soil and environment, such as vibration, noise, etc.

④ How to put forward practical measures from the aspects of material and design to solve the tool wear (including impact and block falling) of shield machine during tunneling in sandy gravel stratum, so as to ensure the reliability of shield machine tool for long-distance tunneling.

Types of cutting tools and cutting principle

At present, the cutting tools of shield machine are divided according to the cutting principle. It is generally recognized that there are two types of hobs and cutting tools (these two types of tools can be further subdivided according to the different properties of tunnel surrounding rock and different cutting purposes). The cutting principle of hob is mainly that the tool breaks rock by extrusion, which is generally used for rock tunnel excavation. Hob cutter can also be used when there is gravel with large particle size (particle size greater than 400mm) passing through loose stratum and the content reaches a certain proportion. In addition, in the case of complex and changeable geological conditions of the tunnel and frequent staggered occurrence of rock (not too high strength) and general soil (or clay or sand), hob cutter may also be used, that is, it is used in composite shield machine.

The cutting principle of the cutting knife is mainly that while the shield machine advances forward, the cutter rotates with the cutter head to produce axial (along the forward direction of the tunnel) shear force and radial (tangential direction of cutter head rotation) cutting force on the soil in front of the excavation face, constantly cutting down the soil in front of the excavation face. The cutting knife is generally applicable to loose strata such as sandy pebble, sandy soil and clay with particle size less than 400mm.