What Does Blind Shield Mean?
A blind shield is a shield used in tunneling operations that has all its sides covering the working face closed, but it has doors that can be opened in order to remove the material from inside. It is a type of earth pressure shield which is pushed into the soil with the help of the cutting edge of the shield.
Trenchless technology utilizes directional tunneling methods to drill holes under the surface of the ground for the purpose of laying pipelines without excavating open trenches, using blind shields to protect the drill operator.
Trenchlesspedia Explains Blind Shield
Blind shields are used in very soft clay and silt and the spoil removal is controlled by an opening present in the advancing face. It does not require a cutting tool. The rate of soil excavation is controlled by the speed of the conveyor. The front resistance pressure on the advancing shield is balanced with the lateral earth pressure by adjusting the rate of advance of the shield, the rate of soil excavation and the total push force.
The diameter of the shield is slightly larger than the diameter of the product pipe or prefabricated lining. As the shield is jacked forward, the linings are installed. The annular space between the shield and the lining is filled with grout.