The Impact of Grain Size on HDD
Grain size in granular soils significantly affects HDD operations, particularly in steering, penetration force, and drilling fluid properties. Larger soil particles, such as cobbles or small boulders, can deflect the drill, increasing resistance and requiring higher loads to maintain the penetration rate. These larger particles can also increase torsional loads on the drill rod, raising the risk of rod torque-off or breakage. As grain size increases, so do the challenges in maintaining a stable drilling path and avoiding equipment damage.