These devices are direct-reading, spring operated instruments used to determine the unconfined compressive strength of cohesive soils. Once pushed into the soil, an indicator sleeve displays the reading. These devices measure a soils cohesion. They consist of vanes that are pressed into a level section of undisturbed soil, and the torsional knob is slowly turned until soil failure occurs. These measurements need to be multiplied by 2 to give unconfined compressive strength.
Careful attention needs to be payed to reading the dial measurement.
This procedure involves an attempt to press the thumb firmly into the soil in question. This is a very subjective test and has a large degree of inaccuracy. Dry Strength Test Dry soil that crumbles freely or with moderate pressure into individual grains is granular. A drying test is used to differentiate between cohesive material with fissures, unfissured cohesive material, and granular material. If the sample develops cracks as it dries, significant fissures are indicated.