Development and laboratory evaluation of a rheometer for soil visco-plastic parameters

A motorized rheometer was developed for determining soil visco-plastic parameters that works on the principle of torsional shear applied to a standard vane with controlled strain rate. Rheological measurements were carried at different soil moisture contents (10%, 13%, 17% and 20% dry basis (gravimetric)) and soil compaction levels (100, 150, 200, 300 and 400 kPa) to find their effects on soil viscosity and yield strength. The values of viscosity of the clay loam soil (29% clay, 24% silt and 47% sand) were found to spread in the range of 53–283 kPa s, and yield stress variation had a span of 4–28 kPa. Increase in soil compaction was accompanied by a sharp increase in soil viscosity, while moisture content affected soil viscosity negatively. Effect of both these parameters was statistically significant (95% confidence interval). Yield stress was positively related to soil compaction and the effect was statistically significant. However, it was negatively related to moisture content and the effect was not statistically significant for the levels of moisture content tested.