The Vane Test is a traditional method of determining the shear strength of saturated soft clay, submitted to undrained loading conditions (Su).

The Test

Standardized by Brazilian ABNT NBR 10905/89 and ASTM D2573-08 Standard test method for field vane sher test in cohesive soil , the test uses a standard size steel vane with a cross-section shaped like a cross. The test consists of driving the vane statically into the soil until reaching the desired position to perform the test.

The vane is driven down using a double rod system to eliminate any friction between the vane rod and the soil and any interference in measuring shear strength.

Once the vane is in place, torque is applied to the blade by a measurement unit at a speed of 0.1 to 0.2 degrees per second. Maximum torque makes it possible to obtain the undrained shear strength value under natural unstrained soil conditions.

Afterwards, the undrained shear strength – representing a post-disturbance clay state – is determined by quickly rotating the vane 10 times consecutively to obtain the undrained strength of the soil under disturbed conditions.

Damasco Penna uses type “A” equipment that guarantees results and precise readings in electronically controlled tests performed without previous boring.

Results

The following results can be obtained by Vane Testing:

• Torque graph according to rotation
• Undrained strength
• Disturbed undrained strength
• Clay structure sensitivity