- Increased fluidity of excavated soil
In gravel layer, rheological foams work as ball bearings and increase the fluidity of excavated soil.
- Reduction of fluctuations in face pressure
The compressive character of rheological foams can reduce fluctuations in face pressure.
- Higher watertightness of excavated soil
The groundwater in void space between soil particles of excavated soil is replaced by tiny foams, so the excavated soil can have higher watertightness.
- Effectiveness in preventing adhesion of excavated soil
In hard, cohesive bedding, adhesion of excavated soil on the shield face plate and inside the chamber is prevented.
- Easy treatment and disposal of excavated soil
Excavated soil is restored to the original state when it was in the ground and therefore can be treated or disposed of easily.
- Improvement of working environment
Neither clay nor bentonite is used, so the tunnel is clean and offers a better working environment.
- Downsizing of equipment
Only small equipment is required for generating and injecting foams.
Principle of Rheological Foam Shield Tunneling Method
Mechanism of tunnel driving
The Rheological Foam Shield Tunneling Method excavates a tunnel while injecting foams into the face and the chamber. Foams are generated with special foaming agent. Injected tiny foams with properties similar to those of shaving cream can improve the fluidity and the watertightness of excavated soil. Foams can also prevent the soil from sticking inside of the chamber. This enables smooth tunnel driving while keeping face stability. In addition, the removed soil with foams can be defoamed and put back the state before foam injection. Then excavated soil can be easily transported and disposed of. Thus, the method also has economic merit.