Field Measurement of Shear Strength of Cohesive Soil By Vane Shear Test - Civil Engineering

Wednesday, 19 September 2018

Field Measurement of Shear Strength of Cohesive Soil By Vane Shear Test

Vane Shear Test On Soil

Vane shear test is a simple and quick test, used either laboratory or in the field.

Aim of Vane shear test 

To determine the undrained shear strength of cohesive soil.

Testing Equipment For vane shear Test

⇰ A vane shear testing equipment consists of four thin plates, called vanes, welded orthogonally to a steel rod.
⇰ A torque measuring arrangement, such as a calibrated torsion spring is attached to the rod. The steel rod is rotated by worm gear and worm wheel arrangement.

The procedure of Vane Shear Test

⇰ A pit is first of all made into the ground up to a depth at which the shear strength is to be tested.

⇰ The vane tester is then pushed or driven carefully into the soil below the bottom of the pit, to a depth somewhat greater than the length of the vane.

⇰ The torque rod is now rotated (usually 1° per minute). The rotation is continued till the soil falls, which will be indicated by the sudden decrease of torque without any back movement of torque wheel.

⇰ The maximum torque (T) given till failure is measured and recorded.
The shear strength (𝛕f) is calculated by using the following equation;

𝛕f = 2T / πd2[ H + d/3]

Where, H = Height of the vane
And, d = Diameter of the vane

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