Field Inspection Vane Shear Tester – Hand Shear Vane for Site Use

Field Inspection Vane Shear Tester - Includes Calibration Report

Complete With Transit Case, T-Handle Apparatus, Small Vane (32mm x 16mm) Medium Vane (40mm x 20mm) Large Vane (50.8mm x 25.4mm) , Dummy Vane, 4 x 500mm Ext Rod, 2 Spanners.

The measuring part of the instrument is a spiral-spring (3), (max. torque transmitted 38kgcm).  When the handle (1) is turned, the spring deforms and the upper part (4) and the lower part (8) of the instrument get a mutual angular displacement. The size of this displacement depends on the torque which is necessary to turn the vane (11). By means of a graduated scale (5) the shear strength of the clay is obtained.  

The lower and upper halves of the instrument are connected by means of threads. The scale (5) is also supplied with threads and follows the upper part of the instruments by means of two lugs. The 0-point is indicated by a line on the upper part (4). When torque is applied, the scale-ring follows the upper part of the instrument and when failure is obtained, the scale-ring (5) will remain in its position due to friction in the threads.

Three sizes of four-bladed vanes (11) are used:

16x32mm (extra) multiply readings with 2
20x40mm (standard) direct readings
25.4x50.8mm (extra) multiply readings with 0.5 
which makes it possible to measure shear strength of 0 to 260, 0 to 130 and 0 to 65 kPa respectively.

The area ratio of the vanes are 14, 16.5 and 24% (ratio of cross sectional area of vane to the area to be sheared).

The vane blades are soldered to a vane shaft (9) which again is extended by one or more 0.5 m (0.49 m) long rods. The connection between the shaft-rods and the instrument is made by threads. To make the connection as straight as possible, the rods have to be screwed tightly together and the threads are to be cleaned.

The maximum shear strength that can be measured with the inspection vane tester is 260 kPa. In clays with this shear strength a force of about 40 to 50 kilos is required to press the vane down into the clay. The vane shaft is designed to take this force, but if extension rods are used, precautions against buckling are required.