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 un-drained 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.

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 grater 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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