Vane Shear Testing (VST) and Fast-Vane
Gregg Drilling operates a number of vane testing systems for testing soils ranging from soft clays to silty tailings deposits.
Geonor Vane System
The Geonor vane shear system is used for testing soft clays in conjunction with borehole drilling and sampling activities.
The Geonor vane system features an up-hole motor to turn the downhole vane and provides a measurement of the in situ undrained shear strength. The system utilizes either a 55mm or 65mm vane based on the expected strength of the soils being tested.
We always recommend the procedure to include evaluating the site with CPTs initially to identify layers and depths where vane testing may be beneficial. Then a drill rig is mobilized with the vane system to drill to these specific depths and deploy the vane down-hole.
Download a PDF outlining Gregg’s Geotechnical Testing Services
Protected iVane System
Gregg also operates a protected iVane system made by A.P. van den Berg that can be deployed using CPT or direct push equipment. This system does not require a drill rig or borehole as the vane is pushed within a protective casing to the desired depth and then advanced past the casing into the clay for testing.
The digital iVane has a down-hole torque motor for improved accuracy especially at larger testing depths. The digital readout displays undrained shear stength vs. rotation to provide a detailed record of the test. The iVane can measure undrained shear strength values up to 14,000 psf (700 kPa) using a 1.2″ (30mm) diameter vane or 900 psf (45kPa) using a 3″ (75mm) vane. It has an accuracy of 0.5% of full scale reading and can vary rotation speeds from a slow 0.1 degrees/second to 12 degrees/second.
Features:
- Torque sensor and drive motor located close to the vane for most accurate measurements
- Entire rod string does not have to be rotated to rotate the vane
- Motor is electronically limited at 100Nm (74 lb-ft) to protect against damage
- Blade sizes available include: 40, 50, 55 and 75mm diameter (2H:1D ratio)
- Accuracy of 0.5% full scale output
Download a PDF of the iVane System
Protected Fast Vane System
For evaluating shear strength in silty materials it is important to maintain an undrained test during operation. Gregg operates a modified digital iVane from A.P. van den Berg called the Fast Vane to accomplish this goal.
Fast Vane Improvements:
- Rotation rates from 1-60 deg/sec
- Ensure test is undrained even in silts
- Various dimensions and sizes based on site conditions (2H:1D with D = 40, 50, 55 or 75mm)
- Data frequency unaffected by rotation rate (data recorded at 0.1 degrees)
- Estimate speed of rotation based on t50 from dissipation tests
Download a PDF of the Fast Vane System
Testing Methodology:
The Vane consists of four rectangular blades fixed at 90° angles that are pushed into the
ground to the desired depth. Once this depth is reached, the blades are rotated at a constant speed (high speed for Fast Vane).
The resistance of the soil, and consequently the required torque, will increase until the soil shears. Shearing happens in milliseconds (Fast Vane) or minutes depending on the rate of rotation. From the point the soil is shearing, the torque value will generally decrease. The highest measured value to shear the soil, is a measure of the undrained shear strength. After the first test to measure the peak undrained shear strength, the soil is remolded by rotating the vane 20 times. Then the test is then repeated to measure the remolded shear strength.
The test fully complies with ASTM D2573.