Penetrometer, Low-Strength Soil Adapter Foot (Tire Gauge Design)
Adapter foot is recommended when testing extremely low strength cohesive soils. 1″ (25mm) dia. foot, compared to the 0.25″ (6.35mm) penetrometer piston, increases the effective area measured by 16 times.
Divide by 16 to obtain correct unconfined compressive strength when the reading in tons per square foot or kilograms per square centimeter is on the low-load side.