Building Construction Handbook, Eighth Edition

Soil Assessmentand Testing

Vane Test ~ this test measures the shear strength of soft cohesive

soils. The steel vane is pushed into

the soft clay soil and rotated by

hand at a constant rate. The amount

of torque necessary for rotation is

measured and the soil shear strength

calculated as shown below.

This test can be carried out within a

lined bore hole where the vane is

pushed into the soil below the base

of the bore hole for a distance equal

to three times the vane diameter

before rotation commences.

Alternatively the vane can be driven

or jacked to the required depth, the

vane being protected within a special

protection shoe, the vane is then

driven or jacked a further 500mm

before rotation commences.

Calculation of Shear Strength †

Formula:- S = M

K

where S = shear value in kN/m^2

M = torque required to shear soil

K = constant for vane

=3„66D^3 � 10 †6

D = vane diameter