Best fit polynomial regression pressure-displacement curves for a sand compacted to different densities at low (<1%), medium (6%), and high (12%) gravimetric moisture content.
| Sand density Mg m−3 | Gravimetric moisture | Equation y =displacement volume (cm3) x = input pressure (kPa) | R2 | Model p value |
|---|---|---|---|---|
| 1.51 | 0.10% | y = −0.0000047x3 + 0.002191x2 + 0.14722x − 0.0776 | 0.86 | <0.001 |
| 1.71 | 0.08% | y = 0.0000005x3 − 0.000279x2 + 0.09127x + 0.0386 | 0.91 | <0.001 |
| 1.64 | 0.10% | y = 0.0000003x3 + 0.00009x2 + 0.02973x + 0.6384 | 0.97 | <0.001 |
| 1.63 | 6.00% | y = −0.0000001x3 + 0.000271x2 + 0.01662x + 0.916 | 0.76 | <0.001 |
| 1.67 | 12.00% | y = 0.0000008x3 − 0.000312x2 + 0.06401x − 0.3949 | 0.92 | <0.001 |