State Materials Office
The Test Pit is a controlled environment structure where soil or recycled materials can be constructed as a model pavement and evaluated. The Test Pits are two 24' x 8' x 7' deep structures that are surrounded by a sump with a interconnecting channel system for controlling the water table. Soils or other materials to be tested are placed, usually in 6" lifts and compacted to a specific density. After all material is in place the water table is adjusted to the desired height. Testing is usually done at three moisture conditions Optimum, Drained and Soaked. This is done to simulate best to worse case field conditions. Once the water table is stabilized, repetitive plate load testing is conducted. Testing consists of loading a 12" diameter rigid steel plate to 20 psi for embankment and subgrade materials and 50 psi for base materials. Load is applied at one hertz intervals for 30,000 cycles with data recorded at selected intervals. Readings are taken of both total and permanent deflections to obtain resilient modulus values. These studies are conducted to evaluate new equipment and/or soils or recycled materials for potential use in the field.