Materials & Tests Division - Laboratory Operations Office Soil Laboratory
Office Hours: 7:30 a.m. - 4:30 p.m. CST
Phone: (615) 350.4181
Fax: (615) 350.4293
The
primary duties of the Soil Laboratory are to test soil and
soil-related materials that are retrieved from proposed, active
or completed state highway construction sites. The data is given
to the Geotechnical Section and used for bearing capacity
calculations (for structure foundation design and pavement
design), slope stability determinations (for compaction and soil
improvements), settlement calculations, and a variety of other
purposes as requested and reported in the Subsurface
Investigation Report. Bulk Sampling, Split-Spoon Sampling, or
Thin-Walled Tube Sampling from various personnel throughout
TDOT, primarily in the Geotechnical Section, submits the
material. As indicated on the laboratory assignment sheet by the
geologist or geotechnical engineer, the soil is tested for
classification and physical properties (strength) according to
design needs. The Soil Laboratory applies the AASHTO method for
sampling and testing soils.
The most common tests performed include:
- Hydrometer Test - conducted on fine grain material to determine particle size for classification and estimating permeability.
- Liquid Limit - used in soil classification and estimates the state at which a soil passes from a solid to a liquid state.
- Plastic Limit - used in soil classification and to estimate the lowest water content at which the material remains plastic retaining strength.
- Standard Proctor Test - determines the optimum moisture and proctor density needed to determine compaction control relative to soil stability, strength, erosion and permeability.
- Specific Gravity - necessary for volume calculations.
- California Bearing Ratio Test - yields soil strength values in sub-base for pavement design.
- Unconfined Compressive Strength - approximates the compressive strength of soils that possess sufficient cohesion for stability and load carrying properties.
- Direct Shear - yields the shear strength of soils as loads are applied.
