Definition - What does Fluid-Assisted Boring mean?
Fluid-assisted boring describes the use of drilling mud, fluid or slurry (used interchangeably) to improve the effectiveness of a horizontal directional drilling (HDD) operation; usually, this fluid is a mix of bentonite. Drilling mud is supplied to the drilling head to assist with breaking up the ground at the tunnel face, as well as to carry the spoils out of the tunnel.
Choosing the appropriate drilling fluid can enable faster drilling.
Trenchlesspedia explains Fluid-Assisted Boring
Drilling fluid helps with tunnel stability by providing a positive pressure against the surrounding soil, and also removes the spoil from the tunnel, thus making pipe installation possible. The combination of the fluid pressure supplied and the rotation of the drilling head creates a more efficient breakdown of the tunnel face and therefore quicker progress through the ground.
Differing ground conditions require different drilling fluid composition in order to suspend the spoil in solution and remove it from the tunnel. Environmental concerns must also be taken into account when using drilling fluid that must later be disposed of properly.