When geotechnical crews perform excavations, it is crucial that engineers determine a safe slope angle, especially in situations where the ground is clay, silt or other fine-grained soils. A simple and quick test that estimates the undrained shear strength of saturated soils is the vane shear test.
A vane shear test is a method of testing soil characteristics on site, or in-situ. The data you get from a vane shear test can help develop guidelines for construction of foundations and other geotechnical needs. Unlike other types of tests, it doesn’t require that a soil sample be taken or the use of additional lab equipment to analyze the soil.
This makes it a popular choice since it requires less time and cost. It is also able to test soft clay found at a great depth where obtaining a sample can be difficult.
The soil sample must be able to retain water throughout the test. The test is not suitable for unsaturated, highly permeable soil or on fissured clay.
The vane test is done by drilling to a depth just above where you want to test the soil. The vane shear is attached to AWJ rods and inserted into the clay or silt. Using a torque wrench, the vane shear is slowly rotated and how much torque is required to shear the soil is measured.
Certain situations may require variations of this test or that the test is repeated. Requesting technical support can save time and money.