| ρd,max | ρwet | w (%) | Target RC (%) | Computed ρd | RC | Status |
|---|---|---|---|---|---|---|
| 1950 kg/m³ | 2050 kg/m³ | 8.5 | 95 | 1890.32 kg/m³ | 96.9% | PASS |
| 1900 kg/m³ | 1980 kg/m³ | 11.0 | 98 | 1783.78 kg/m³ | 93.9% | FAIL |
| 120 pcf | 125 pcf | 7.0 | 95 | 116.82 pcf | 97.4% | PASS |
- Select your density units and enter ρd,max from the lab test.
- Enter the field wet density and the measured water content w (%).
- Set the target RC (%) from your project specification.
- Optionally add wopt, lift thickness, roller type, passes, and Gs.
- Press Submit. Results appear above the form for quick review.
- Use Download CSV or Download PDF for documentation and sharing.
Compaction Quality Metrics
Relative compaction compares field dry density to laboratory maximum dry density. Many earthfill specifications require 90–95% for general embankments and 95–98% for structural backfill. Use “RC minus target” to decide acceptance, rework, or added rolling. Also review the required wet density at current moisture, because crews measure wet density in the field. For critical areas, confirm the correct Proctor curve (standard or modified), correction factors, and acceptance method. A small density increase can significantly improve CBR, modulus, and settlement control overall.
Moisture Control and Workability
Moisture strongly influences achievable density, strength, and permeability. When field water content is below optimum, soils may ravel, break down poorly, and need water addition plus mixing. When above optimum, pumping, rutting, and equipment bogging increase, and dry density often drops. The optimum comparison helps plan watering rates, aeration time, and re-test timing, especially for cohesive fills.
Field Testing and Data Consistency
Wet density is commonly obtained by sand cone, nuclear gauge, rubber balloon, or drive cylinder methods. Water content should be sampled from the same lift and time window as density testing. Mixing test methods, testing near edges, or delayed moisture sampling can bias computed dry density and compliance. Check for outliers by repeating tests and comparing multiple locations within a lift.
Lift Thickness and Compactive Effort
Thin, uniform lifts compact more reliably than thick lifts. Roller choice matters: smooth drum works well on granular soils, while padfoot or sheepsfoot improves kneading in cohesive soils. Pass patterns should include overlap and consistent speed. If lifts exceed typical ranges, reduce thickness, increase passes, or adjust moisture to reach the target without crushing aggregate or creating laminations.
Reporting, Traceability, and Audits
Quality records should capture stationing, lift ID, elevation, test method, material source, moisture, densities, and acceptance status. Exported tables help standardize reporting and reduce transcription errors. Pair results with nuclear gauge standard counts, sand cone calibration checks, and daily production notes. Consistent documentation supports payment quantities, claims defense, and long-term performance reviews.
1. What is relative compaction (RC)?
RC is the field dry density divided by the laboratory maximum dry density, multiplied by 100. It shows how closely earthfill matches the compaction reference test.
2. Why does the calculator ask for wet density and moisture?
Field tests often provide wet density. Moisture is needed to convert it to dry density, which is the value used for compaction compliance.
3. How should I select a target RC value?
Use the project specification and soil zone requirements. General embankment targets are often lower than structural backfill, subgrade, or utility trench zones that demand higher stiffness.
4. What if moisture is far from optimum?
Dry soils may need water and mixing for particle rearrangement. Wet soils may require aeration, scarifying, or thinner lifts. Re-test after conditioning to avoid false failures or rework.
5. Can I enter densities in pcf?
Yes. Select pcf units and enter both maximum dry density and wet density in pcf. Results and required values will display and export in the same units.
6. How accurate are the void ratio and saturation outputs?
They are estimates that depend on the provided specific gravity and the assumption of water density at 1000 kg/m³. Use them for screening and trends, not as a substitute for lab phase relations.