Laboratory vane apparatus
Matest Laboratory Vane apparatus represents a valid alternative to the most common standard triaxial equipment whenever a rapid estimation of the undrained shear strength of a soil specimen is required.
Based on the original design by the UK Transport Research Laboratory, this apparatus is hand-operated thus allowing the application of stress to the soil sample as a function of the specific calibration spring and vane used (see accessories).
Choice of the spring and vane to be used is made according to the specific soil strength which is expected to result from the test, however, larger vanes are demonstrated to be suitable when soils having low-strength values are considered.
The working principle of the apparatus is governed by the rotation of the vane into the soil sample, while the calibrated spring provides the measurement of the applied torque. In addition, two different graduated scales are present on the instrument; one for the applied torque (inner scale) and another for the vane rotation (outer scale).
As a matter of fact, the applied load can be obtained in two ways. The first one is based on the use of the relevant calibration charts which directly correlate the angular deflection values with the torque values. The second one can be used when the spring calibration constant (i.e. the slope of the curve on the chart) is multiplied by the angular deflection which is read directly on the dedicated graduated scale.
Finally, at the end of the test, the Undrained Shear Strength (cu) is calculated by a formula dividing the applied Torque (T) by a constant (K) which directly depends on the dimensions and shape of the chosen vane. This way, a reliable result is obtained in a very quick and economical way if compared to the huge investment of space and time which are involved in common triaxial testing procedures.
The vane apparatus is supplied complete with four calibrated springs and a vane Ø 18.7 x 12.7 mm.
Dimensions: 200x250x600 mm
Weight: 7.5 kg approx.