What is the Micro-Tunneling Technologies?

The micro-tunneling boring machine, jack the pipe, and excavate the soils. When computerization is combined with slurry Micro-Tunneling's ability to balance both groundwater and earth pressures, you have a truly revolutionary tunneling method for installing 18” to 96” OD tunnels.

The micro-tunneling method can be either “one pass” with the permanent carrier pipe jacked directly in place or “two-pass” with a permanent carrier pipe installed inside a temporary tunnel casing jacked in place. One pass is the most efficient and least costly method of tunneling. Pilot tube micro-tunneling (PTMT), also known as guide bore Micro-Tunneling (GBM), combines the accuracy of visual theodolite guidance with the cost advantages of ultra-small access shafts (<12’ OD) and one pass pipe jacking of 6” to 30” OD carrier pipes. Guided auger boring uses the same pilot tube system as PTMT/GBM to install auger bored steel casing up to 48” in diameter within 1”+/- of the designed elevation and alignment.

The Micro-Tunneling technologies can be divided into 2 ways :

1. Slurry Balance Shield Tunneling.

Slurry Balance Shield Tunneling is used to stabilize the excavation surface by pressurizing mud or mud (usually bentonite suspension). There is a sealed partition behind the cutter head, forming a mud-water chamber between the excavation surface, which is filled with mud. The excavated soil and mud are mixed by mud pump and transported to the separation plant outside the tunnel, and the mud is reused after separation.

2. EPB ( Earth Pressure Balanced Tunneling )

For soft, cohesive soils tunnel boring machines with earth pressure support are a preferred option. So-called Earth Pressure Balance Shields (EPB) turn the excavated material into a soil paste that is used as a pliable, plastic support medium. This makes it possible to balance the pressure conditions at the tunnel face, avoids uncontrolled inflow of soil into the machine, and creates the conditions for rapid tunnelling with the minimum settlement.