The Purpose of the Shear Vane Test

Equipment

• The equipment used in a shear vane test consists of four rectangular steel sheets arranged at right angles around a stainless steel rod. The rod is created at a size no larger than 2.5 mm wide and about 60 mm tall, the civil engineering information website The Constructor reports. The rectangular sheets that complete the shear vane equipment are constructed to a size of twice the length compared to the width of the steel sheets. Shear vane test equipment was developed in Scandinavia and in the U.S. is subject to standards for the manufacture and use of the equipment, developed by the American Society for Testing & Materials.

Test

• The shear vane test is completed by inserting the test equipment into the fully saturated soil and turning at a rate of about 0.1 degree per second. After completing a full turn, the torque required to move the equipment through the saturated soil is measured. A second measurement is taken by turning the shear vane test equipment quickly through the saturated soil through 10 revolutions. Following the rotations, the initial test of turning through 0.1 degrees per second and the torque measurement is again recorded for comparison.

Disadvantages

• The shear vane test is used by engineers estimating the strength of embankments, with the test providing success in estimating the strength of a soil where the engineer has experience of working in an environment, the University of Connecticut reports. Problems with the test have included overestimation of the shear strength of a location by completing the test in soil with shell and sand pockets that do not provide an accurate measurement of the shear strength.

Use

• The use of the vane shear test can be completed within a laboratory as a quickly completed and inexpensive test to gain the shear strength of any soil structure. The method is often completed in the testing of soil sensitivity for clay-based soils and can be completed for other types of earth formations with a known low shear strength. The shear vane test can be used for low shear-strength soils.