Library / Terramechanics and off-road mobility / TER-22
Terramechanics and off-road mobility
Remoulded cone index
Cone index of soil after it has been churned by vehicle passes, found from the original cone index and the remoulding index.
- Ref
- TER-22
- Rev
- v1
- Field
- Terramechanics and off-road mobility
- Result
- RCI [kPa]
The remoulded cone index RCI = CI × RI is the cone index of soil after traffic has churned it. RI is a dimensionless remoulding index; below 1 the soil weakens under traffic. The cone index is a pressure, here in kPa; to use the empirical WES expressions that expect psi, convert with CI(kPa) = 6.894757 × CI(psi) and keep the input convention each expression asks for. Compare RCI against the vehicle cone index for the same pass count.
Cone index of soil after it has been churned by vehicle passes, found from the original cone index and the remoulding index. A remoulding index below one means the soil weakens under traffic.
Calculator
- Remoulded cone index in psi34.81 psi
- Undrained strength estimate, RCI/1024 kPa
What drives the result
Each variable is moved across its typical range while the others stay at the values above. The longest bar is the key driver.
- Soil with a cone index of 300 kPa and a remoulding index of 0.8 has an RCI of 240 kPa (34.81 psi). Compared with a tracked vehicle’s VCI of 29.25 psi for one pass, it still passes. Against about 82.3 psi for 50 passes, it does not.
- A soil that loses 20 % of its strength under traffic can fail a convoy even though the first vehicle crossed it easily.
Chart data as tables
Ranked variables
| Variable | Typical range | Lowest result | Highest result | Swing (kPa) | Local step | Change in result |
|---|---|---|---|---|---|---|
| CI Cone index | 50 to 1,500 kPa | 40 | 1,200 | 1,160 | +10% | +10 % |
| RI Remoulding index | 0.3 to 1.5 | 90 | 450 | 360 | +10% | +10 % |
Sweep of Remoulding index
| Remoulding index | Remoulded cone index (kPa) |
|---|---|
| 0.3 | 90 |
| 0.45 | 135 |
| 0.6 | 180 |
| 0.75 | 225 |
| 0.9 | 270 |
| 1.05 | 315 |
| 1.2 | 360 |
| 1.35 | 405 |
| 1.5 | 450 |
Sweep one variable
Variables and how each one contributes
Remoulded cone index
What the equation gives you. Everything else feeds it.
Cone index
The cone index measured in the undisturbed soil, in kPa. Raises the remoulded cone index in proportion. Raising it by 10 % (to 330) moves the result by +10 %, from 240 to 264 kPa.
Remoulding index
The remoulding index, a plain number. Often 0.5 to 1 for clays that weaken when churned; above 1 for soils that firm up. Raises the remoulded cone index in proportion. Raising it by 0.1 (to 0.9) moves the result by +12.5 %, from 240 to 270 kPa.
Worked example with the values above
- Multiply: CI × RI = 300 × 0.8.
- RCI = 240 kPa.
- In psi that is 34.81 psi (divide by 6.894757).
Assumptions and limits
- The remoulding index is for the same soil and moisture condition as the cone index.
- The cone index and the vehicle cone index to be compared are in the same units.
Common mistakes
- Comparing RCI in kPa directly with a VCI in psi.
- Using the undisturbed cone index to judge the later vehicles in a convoy.
Statistics and uncertainty
Cone index readings scatter by ±15 % across a site and with moisture, and RI is itself an empirical average, so RCI is uncertain by at least that. Take several readings and use a conservative value.
Where it is used
- Predicting whether soft ground will carry later vehicles after the first ones have passed.
- Comparing RCI with VCI for go or no-go screening.
Maths you need
- Cone index: penetrometer resistance of soil
- Unit conversion: 1 psi = 6.894757 kPa