Rapid Shear Strength Determination 3 Vanes Provided for Varying Soil Consistency Easy to Use in Field or Laboratory Sample Trimming Eliminated The Slope Indicator Torvane is a soil testing instrument for the rapid determination of shear strength of cohesive soils either in the field or laboratory. Applications for evaluation of shear strength include sides of test pits, ends of Shelby tube samples, standard penetration samples, split spoon samples chunk samples from test pits and backhoe excavations, and triaxial or consolidation tests in the laboratory on undisturbed thin-wall tube samples.The Torvane consists of a disc (vane) with blades on the lower surface which is pressed into the soil to be tested. When the upper knob, which is attached to the disc through a precision helical spring, is rotated with finger pressure, a torque is applied to the disc. The torque is resisted by shear stresses in the clay or soil across the lower face and around the circumferential area of the blades. The calibrated dial converts torque directly into shear stress in kilograms per square centimeter (kg/cm2). The maximum reading on the dial is the shear strength of the soil.