Expansive soils, dominated bymontmorilloniteand illite, feature “20% swelling when wet and 15% shrinkage when dry,” posing three major threats to water well drilling rig operations:
Borehole wall rheological failure: When water content rises, expansive soils become plastic-flowing, with borehole shrinkage at 5cm/h.
Swelling-shrinkage cycle damage: Wet-dry alternation creates network cracks in the borehole wall, increasing collapse risk by 40%.
Drill tool viscous resistance: Clay particles adsorb to drill pipes, making lifting resistance 3 times higher than in ordinary formations.water well drilling rig
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