What are the advantages of injecting lubricants (bentonite/polymers) in pipe jacking?

Q: What are the advantages of injecting lubricants (bentonite/polymers) in pipe jacking?

The injection of lubricants (bentonite and/or polymers) in pipe jacking reduces friction between the pipe and the ground, reduces the thrust required and reduces the risk of clogging. This helps maintain the integrity of pipe and joints, improves continuity of progress and may allow longer drives or reduce the need for intermediate wells. In addition, well-controlled lubrication helps to stabilize the immediate environment of the pipe and to limit incidents associated with ground loss, especially in sensitive environments.

At pipe jacking (microtunneling), Injection of lubricants (bentonite and/or polymers) is applied to create a lubricant film in the annulus between the pipe and the ground, reducing direct contact and stabilizing the immediate environment of the pipe.

Main advantages:

Less friction = less thrust and less risk of clogging. By lowering the perimeter friction, the thrust required and the likelihood of “blocking” in long drives or demanding terrain is reduced. This translates into greater continuity of progress and fewer critical stops.
Allows longer drives or reduces the need for intermediate wells. If you control friction with well-designed lubrication, you can keep thrusts within allowable limits for more meters (and better decide if additional wells are needed). Related to the sizing of attack and reception wells.
Protects the pipe and, above all, the joints. Less thrust and less local friction reduce the risk of overstressing, seal damage and leakage (especially in long spans and/or tight tolerances).
Improves ground stability around the pipe and helps control seating. Keeping the annulus “worked” with lubricant can limit volume losses and discontinuities around the conduit, especially when combined with stable operation and parameter control.
Improved performance in difficult terrain.
- The bentonite usually provides a stable suspension that reduces friction and can cake in more permeable soils.
- The polymers are often used as a complement to adjust rheology/adhesivity and improve performance in certain fines or mixed soils (as appropriate).
More productivity and predictability. Properly executed lubrication reduces peak thrust, variability and downtime, which improves production and risk control (see geotechnical risks and mitigation y key machinery in pipe ramming).

Technical note: lubrication must also be control it (injection points, flow rates and pressures) to avoid unwanted overpressures or losses to the ground; therefore, it is usually defined within the approach of Technical assistance and engineering.