GES recently purchased additional direct shear testing equipment to add to our growing lab. Maybe it’s because I spend most of my waking hours around dirt and rocks that I find this purchase newsworthy, but I believe you too will find GES’ new equipment exciting once you learn about its capabilities.
First of all, it’s important to understand what a direct shear test is and why they are needed. These tests are performed to evaluate the consolidated-drained shear strength of a sandy to silty soil. The shear strength is one of the most important engineering properties of a soil and is needed whenever performance of a structure is dependent on the soil’s shearing resistance. The shear strength is needed in engineering calculations to determine the stability of slopes or cuts, find the bearing capacity for foundations, and calculate the pressure exerted by a soil on a retaining wall.
Now back to the new equipment; it’s computer controlled! In the geotechnical world of testing dirt, this is exciting news because most of the lab testing is done manually and is a tedious process. Having a computer-controlled direct shear machine allows more testing capacity, a quicker turn-around time, more precise data collection with more accurate results and an overall increase in productivity for the GES lab.
In addition to the direct shear equipment, GES also added more consolidation racks to our inventory. A consolidation test is performed to characterize the magnitude and rate of volume decrease that a laterally-confined soil specimen undergoes when subjected to increasing vertical pressures. From the measured data, the consolidation curve (pressure-strain relationship) can be plotted. This data is useful in determining the compression index, the recompression index and the preconsolidation pressure (or maximum past pressure) of the soil. In addition, the data obtained can also be used to evaluate the coefficient of consolidation and the coefficient of secondary compression of the soil.
The consolidation properties obtained from the consolidation test are used to estimate the magnitude and the rate of both primary and secondary consolidation settlement of a structure or an earthfill. Estimates of this type are of key importance in the design of engineered structures and the evaluation of their performance.
The new machines have pneumatic controlled loading and have digital logging capabilities. This allows GES to increase our production while providing more detailed test results.