Introduction to Shield Cutting Tools (II)

source：http://www.xrocktools.com/ Release Time：2015-01-11 09:59:24

1. Imitation knife

Shield tunneling machines are generally designed with two imitation knives (one spare) arranged at both ends of the spokes. During construction, the profiling tool can be extended and retracted radially from both ends of the spoke according to the requirements of the amount and range of over excavation, in order to achieve the purpose of profiling cutting. The maximum extension of the imitation knife is generally between 80 and 130mm. When the shield machine advances, turns, or corrects in curved sections, it creates the required space by copying over excavation and cutting the soil, ensuring that the shield machine achieves curved advancement, smooth turning, and correction under the conditions of less over excavation and minimal interference with the surrounding soil.

2. Roller cutter

Based on the experience of subway construction in Guangzhou and Shenzhen, with the extension of urban rail networks and the increase in construction efforts, shield tunnel sections not only need to pass through common weak strata, but also need to pass through some hard rock sections. Therefore, when selecting cutting tools, it is necessary to consider both the needs of excavation in soft rock and the requirements in hard rock. It is generally believed that scrapers are suitable for soil layers and some soft rocks, while disc cutters are suitable for hard rocks. Among them, single blade cutters can be used in high-strength rocks, and there are engineering records of their application in rocks with compressive strength exceeding 200 MPa abroad.

The disc-shaped rolling cutter installed on the cutterhead is tightly pressed against the rock surface under the action of a jack. As the cutterhead rotates, the disc-shaped rolling cutter revolves around the center axis of the cutterhead while also rotating on its own axis. The rolling cutter cuts a series of concentric grooves on the palm surface under the thrust and torque of the disc. When the thrust exceeds the strength of the rock, the rock under the tip of the disc-shaped rolling cutter breaks directly, and the tip penetrates the rock, forming a crushing zone and radial cracks; Further pressure is applied, and when the distance S between the rolling cutters meets certain conditions, cracks in the rock between adjacent rolling cutters extend and interconnect, forming rock fragments and collapsing. The disc-shaped rolling cutters complete a rock breaking process.

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