The Atterberg limits define the boundaries
of several states of consistency for plastic soils.
The boundaries are defined by the amount of water
a soil needs to be at one of those boundaries. The
boundaries are called the plastic limit and the liquid
limit, and the difference between them is called the
The direct shear test determines the
consolidated, drained strength properties of a sample.
A constant strain rate is applied to a single shear
plane under a normal load, and the load response is
measured. If this test is performed with different
normal loads, the common shear strength parameters
can be determined.
This is done to determine the soil
gradation. Coarser particles are separated in the
sieve analysis portion, and the finer particles are
analyzed with a hydrometer. The distinction between
coarse and fine particles is usually made at 75 µm.
The sieve analysis shakes the sample through progressively
smaller meshes to determine its gradation. The hydrometer
analysis uses the rate of sedimentation to determine
Maximum Dry Density
(MDD) & Optimum Moisture Content (OMC)
These tests are used to determine
the maximum unit weight and optimal water content
a soil can achieve for a given compaction effort.
California bearing ratio
A test to determine the aptitude of
a soil or aggregate sample as a road subgrade. A plunger
is pushed into a compacted sample, and its resistance
Triaxial shear tests
This is a type of test that is used to determine the
shear strength properties of a soil. It can simulate
the confining pressure a soil would see deep into
the ground. It can also simulate drained and un drained
Unconfined compression test
This test compresses a soil sample
to measure its strength. The modifier "unconfined"
contrasts this test to the triaxial shear test.