Measurement of Peat Soil Shear Strength Using Wenner Four-Point Probes and Vane Shear Strength Methods

Table 1

Major source of error in the vane shear test.

Cause	Effect	Influence on Strength Measurement
Damaged zone	Disturbed soil excessively	Decreases optimum strength
Vane rotated too fast	Soil sheared too fast	Increases
Friction between torque rods and soil or casing	Measure torque includes a spurious component of resistance	Increases
Poorly calibrated torque measurement	Inaccurate torque	Increases or Decreases
Test performed in disturbed soil	Soil structure is broken down	Decreases
Isolated gravel/cemented nodules	Measured torque includes a spurious component of resistance	Increases
Unknown sand/silt/shell lenses	Drainage during test	Increases