Pressurized Tunnel Bore Machines Mean?
Pressurized tunnel boring machines (PTBM) are machines specially designed to maintain face stability while drilling, through the use of air or water pressure. Pressurized tunnel boring machines are designed to meet the unique demands of drilling in soft or unconsolidated soils as well as in areas that are sensitive to ground movement.
Trenchlesspedia Explains Pressurized Tunnel Bore Machines
If a water mixture is used, it is known as a slurry shield or a slurry boring machine. Earth balance pressure (EPB) tunnel shields use excavated soil at the face to mix with a man-made paste. In both cases, the pressurized slurry and paste mixture is applied through forced jacking until the pressure in their isolated chambers matches the pressure at the working face. In trenchless construction, these processes serve to maintain stability and minimize ground movement.