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Push-in shear vane
Lankelma’s Geonor push-in shear vane was developed as a quick and cost-effective method of measuring the in-situ undrained shear strength of soft to firm clays.
The vane itself is attached to the end of a series of rods, and is comprised of four blades arranged in a cruciform design. The rods advance to the specified depth and then the assembly is rotated at a constant speed. It is the turning moment, or torque, and the angular rotation that is recorded for each test; as the vane rotates, the soil fails along a cylindrical surface passing the edges of the vane and along the horizontal surfaces at the top and the bottom of the blades. Using the torque readings and the known dimensions of the blade, undrained shear strength can be determined.
Two vane sizes are available: 110 mm x 55 mm, applicable for firm soils, and 130 mm x 65 mm for very soft and soft soils. Both incorporate a protection shoe at the leading edge, not only for protection but also for cleaning purposes before each measurement to eliminate the need to withdraw between tests.
The push-in shear vane is a simple but effective method of measuring undrained shear strength of clay material with minimal disturbance, making it a popular technique in geotechnical investigations.