Manual Tests
Manual testing involves evaluating a sample of soil from the excavation to determine qualities such as cohesiveness, granularity, and unconfined compressive strength.
Soil can be tested either on site or off site but should be tested as soon as possible to preserve its natural moisture.
Manual Test Examples
Plasticity Test
This is sometimes called the "pencil test." Shape a sample of moist soil into a ball and try to roll it into threads about 1/8-inch in diameter. Cohesive soil will roll into 1/8-inch threads without crumbling.
Dry Strength Test
Hold a dry soil sample in your hand. If the soil is dry and crumbles on its own or with moderate pressure into individual grains or fine powder, it’s granular. If the soil breaks into clumps that are hard to break into smaller clumps, it may be clay combined with gravel, sand, or silt.
Thumb Penetration Test
Hold a dry soil sample in your hand. If the soil is dry and crumbles on its own or with moderate pressure into individual grains or fine powder, it's granular.
If the soil breaks into clumps that are hard to break into smaller clumps, it may be clay combined with gravel, sand, or silt.
This test roughly estimates the unconfined compressive strength of a sample. Press your thumb into the soil sample. If the sample resists hard pressure it may be type A soil. If it's easy to penetrate, the sample may be type C.
Pocket Penetrometers
Pocket penetrometers offer more accurate estimates of unconfined compressive strength. These instruments estimate the unconfined compressive strength of saturated cohesive soils.
When pushed into the sample, an indicator sleeve displays an estimate in tons per square foot or kilograms per square centimeter.
Knowledge Check Choose the best answer for the question.
1-9. Which of the following manual test results indicates Class C soil?
You forgot to answer the question!