Analysis of TBM and Roller Cutter Tunneling Process

The application of tunnel boring machine (TBM) construction technology in the construction of hydraulic engineering tunnels can realize continuous and rapid operation. In the process of excavation, it has little disturbance to the surrounding rock, the excavation surface is smooth and smooth, and the over and under excavation is less, which can effectively reduce the risk of geological disasters.

It has the advantages of fast speed, excellent quality, low cost and safe construction, and is widely used in water conservancy, hydropower, urban construction, transportation and other industries.

Ⅰ. Drive the TBM roller cutter to squeeze the rock mass 

From the initial crushing zone, the crack begins to appear and gradually spreads to the periphery. When the TBM cutter head is continuously forward and rotated by the drive system, the rock mass is continuously applied to the palm surface in the form of propulsion force and torque, and the continuous crushing zone appears on the TBM cutter disc path. 

As the penetration of the TBM cutter increase, the scope of the lateral crushing zone increases, the crack spreads around, and the two adjacent crushing zones gradually approach each other. When the cracks are connected or the cracks extend to the free surface, rock fragments are formed, out of the rock mass, the rock was broken successfully.

It reflects the interaction between two adjacent disc cutters, the crack development process, and the separation of rock fragments from the rock mass to achieve the purpose of rock breaking.

Ⅱ. Cracks appear in the rock mass between the TBM roller cutter, and the rock falls off

The TBM roller cutters contact and squeeze the rock mass under the action of the forward thrust of the boring machine. Stress concentration occurs near the tip of the cutters, and a dense core is gradually formed. The stress spreads into the rock mass, resulting in cracks of different sizes.

During the tunneling process, the TBM cutter head is rotated by hydraulic drive, and at the same time, the roller cutters on the cutter head rotate, and the roller cutters continuously squeeze and crush the surface of the rock mass.

Under the thrust of the jack, the TBM crushes the rock mass, and drives forward section by section to form a tunnel section. The crushed rock mass is brought into the opening on the cutter head by the bucket (bucket teeth) and discharged to the engine room, it is finally transported out through the slag discharge system.

Microscopically, under the force of the roller cutters, the rock mass begins to change elastically, and a dense core appears, and the dense core sinks continuously.

The cracks continue to expand around until the surface of the rock mass, or connect with other cracks formed under other TBM roller cutters, and the rock fragments begin to fall off and leave the rock mass. To achieve the final ideal effect of excavation.

The microscopic change process of the rock mass can be divided into:

1. The rock mass is subjected to external force, and the internal elastoplastic deformation begins.

2. The rock mass starts to crack and collapse when the stress limit is reached.

3. Then the rock mass is gradually compacted, dense nuclei appear, and larger cracks begin to expand.

4. The cracks are connected to each other and begin to fall off, producing fractured rock flakes.