Testing output versus the expected polynomial regression model sand displacements at input level 400 kPa. Low, medium, and high descriptors were used to distinguish intended treatment levels. XX = Input level for density 1.51 that was limited to 350 kPa since sand displacement volumes exceeded measurement capacity and are considered unreliable. Subscripts of different letter for testing output displacement were different at α = 0.05 in Oneway AOV. Testing output was consistent with model outputs in the 400 kPa root inflation pressure.
| Sand Density Mg m−3 | Gravimetric moisture | Observed Displacement (cm3) @ 400 kPa ± Std. error | Model Displacement (cm3) @ 400 kPa ± confidence interval a = 0.05 |
|---|---|---|---|
| 1.51 (low) | 0.10% (low) | ----- | 106 ± 31 XX |
| 1.71(high) | 0.08% (low) | 23 ± 2a | 23 ±1 |
| 1.64 (med) | 0.10% (low) | 48 ± 2b | 49 ± 2 |
| 1.63 (med) | 6.00% (med) | 48 ± 7b | 43 ± 2 |
| 1.67 (high) | 12.00% (high) | 28 ± 5a | 28 ± 1 |