Introduction

The Torvane shear device (ELE International model 26-2261, Figure 1) enables the user to quickly determine the shear strength of cohesive soils.
Three sizes of vanes are supplied with torvane:
- The standard vane (25.4 mm diameter), has a stress from 0 to 1 kg/cm2, this is also the approximate range of torque that can be easily applied by finger pressure. It is used for fully saturated cohesive soils with undrained strength independent of normal pressure. The stress range permits it to be used for clays varying in consistency from very soft to stiff.
- The sensitive vane (47.5 mm diameter), is provided for use with remolded samples. It is for a range of 0 to 0.2 kg/cm2. It has a ratio of 0.2.
- The high-capacity vane (19 mm diameter), It is used with stiffer clays. It is for a range of 0 to 2.5 kg/cm2. It has a ratio of 2.5.

Figure 1.- Torvane shear device (ELE International)

The pocket penetrometer was develop by Soiltest Inc. for use for field engineers to check the visual classification of soils. The readings of the penetrometer were compiled from several thousand unconfined compression tests of silty and clay-like soils.

Procedures - Measuring the Sample

Torvane

Select the appropriate vane size and fit to vane driver (Figure 2).

Figure 2.- Vane driver and the 3 kinds of vanes.

2. Make sure zero on dial is aligned with index mark on knob (Figure 3), rotating a counter-clockwise the dial face.

Figure 3.- Dial aligned.

3. Test the surface, should be reasonably flat and least two inches in diameter.

4. Press torvane into soil to depth of blades and maintain a constant vertical pressure while turning knob (Figure 4). A rate of rotation such that failure develops in five to ten seconds is recommended.

Figure 4.- Shearmeter correct position.

5. After failure develops, release the remaining spring tension slowly and the index mark on the knob will indicate the maximum shear value (Figure 5).

Figure 5.- Result at the end of the measurement.

Penetrometer

Slide the red-ring, on the barrel of penetrometer, down against the instrument handle (Figure 6). This ring will hold the maximum reading of the scale, for easy reading.

Figure 6.- Red-ring in position to start measurement.

2. Grip the penetrometer by the handle and push the tip into the soil to the mark located ¼'' from the tip (Figure 7).

Figure 7.- Mark on the tip of the penetrometer.

3. Read the unconfined compression strength directly in tons per square foot (TSF) or kilograms per square centimeter (kg/cm2) from the scale. The reading is located in the red ring, side closest to the knurled handle (Figure 8).

Figure 8.- Result at the end of the measurement.