Sand Cone Field Density Test Calculator
Enter the sand-cone apparatus readings, moisture-tin weights, and laboratory maximum dry density. The calculator reduces the test to hole volume, wet and dry density, relative compaction, and a pass or fail margin.
Relative compaction96.63%
- Acceptance result and margin
- PASS: 1.63 percentage points above required compaction
- Sand mass in test hole (lb)
- 6
- Test-hole volume (ft3)
- 0.06
- Soil water content
- 11.11%
- Field wet density (lb/ft3)
- 128.83
- Field dry density (lb/ft3)
- 115.95
- Required dry density (lb/ft3)
- 114
- Required wet density at measured moisture (lb/ft3)
- 126.67
Check ASTM particle-size limits, minimum test-hole volume, apparatus calibration, and project acceptance rules separately.
The pass or fail result applies only when the field material matches the material represented by the laboratory maximum dry density.
How to use this calculator
- Enter the calibrated bulk density for the same test sand used in the apparatus.
- Enter the before and after apparatus masses and the cone and base-plate correction.
- Enter the moist soil mass recovered from the hole and the three moisture specimen masses.
- Enter the laboratory maximum dry density and required compaction from the project documents.
- Review the density, compaction, and notes before treating the result as an acceptance check.
How the sand-cone result is calculated
The sand-cone method uses calibrated sand to measure the volume of the test hole. The apparatus loses sand during the test, but part of that sand only fills the cone and base-plate space. That calibrated cone correction is subtracted before the hole volume is calculated.
The sand placed in the test hole is:
Mh = (A0 - A1) - C
- A0 is the apparatus-and-sand mass before the test.
- A1 is the apparatus-and-sand mass after the test.
- C is the cone and base-plate correction mass.
- Mh is the mass of sand that filled the hole.
The test-hole volume is Vh = Mh / rho_s, where rho_s is the calibrated bulk density of the sand. The field wet density is then rho_wet = M / Vh, using the moist soil mass removed from the hole.
Moisture correction and relative compaction
The water content comes from the moisture container readings:
w = (Ww - Wd) / (Wd - Tw)
Tw is the empty tare mass, Ww is the container plus wet specimen, and Wd is the container plus dry specimen. The calculator reports water content as 100w.
Dry density removes the measured water from the wet density:
rho_dry = rho_wet / (1 + w)
Relative compaction compares field dry density with the approved laboratory maximum dry density:
Pc = 100 x rho_dry / rho_max
The required dry density is rho_req = rho_max x Pt / 100, where Pt is the required compaction percentage. The required wet density at the measured moisture is rho_wet,req = rho_req x (1 + w). The acceptance margin is Pc - Pt, so a zero or positive margin is shown as pass.
What moves the result most
The result is sensitive to the sand calibration, cone correction, recovered soil mass, and moisture content. A small error in the hole volume changes both wet and dry density. A moisture specimen that is too small, contaminated, or weighed in the wrong order can also shift dry density enough to change the pass or fail result.
Relative compaction can calculate above 100 percent. That may be possible on some projects, but it should trigger a check of the sand calibration, moisture result, recovered soil mass, laboratory maximum dry density, and whether the field material is represented by the laboratory curve.
What this calculator leaves out
This tool does not decide whether the sand-cone method is suitable for the soil. It does not check maximum particle size, minimum test-hole volume, sand gradation, apparatus calibration records, oversize corrections, or moisture-test validity. It also cannot decide which Proctor method, laboratory maximum dry density, acceptance percentage, or agency rule applies to the work.
Worked example
Suppose the calibrated sand bulk density is 100 lb/ft3. The apparatus and sand weigh 15.00 lb before the test and 8.00 lb after the test, and the cone correction is 1.00 lb. Sand in the hole is (15.00 - 8.00) - 1.00 = 6.00 lb, so the test-hole volume is 6.00 / 100 = 0.060 ft3.
If the moist soil recovered from the hole weighs 7.73 lb, the field wet density is 7.73 / 0.060 = 128.83 lb/ft3. For the moisture specimen, a 0.100 lb tare, 0.600 lb wet mass with tare, and 0.550 lb dry mass with tare give w = (0.600 - 0.550) / (0.550 - 0.100) = 0.1111, or 11.11% water content.
The field dry density is 128.83 / 1.1111 = 115.95 lb/ft3. With a laboratory maximum dry density of 120.0 lb/ft3 and a 95.0% requirement, relative compaction is 96.63%. The required dry density is 114.00 lb/ft3, so the result is pass by 1.63 percentage points.
Common questions
How is sand-cone test-hole volume calculated?
The apparatus mass lost during the test is the total sand dispensed. Subtract the calibrated cone and base-plate correction to get the sand that filled only the hole. Divide that sand mass by the calibrated bulk density of the sand to get the hole volume.
Why is cone correction subtracted from the dispensed sand?
The sand-cone apparatus fills the excavated hole and also fills the cone and base-plate opening above the hole. The cone correction represents that extra sand. Subtracting it keeps the calculated volume tied to the excavated hole only.
How do I calculate moisture content from tare, wet, and dry weights?
Subtract the dry specimen plus tare from the wet specimen plus tare to get water mass. Subtract the tare from the dry specimen plus tare to get dry soil mass. Water content is water mass divided by dry soil mass, usually reported as a percentage.
Can field compaction exceed 100% of maximum dry density?
The calculation can exceed 100% when the measured field dry density is greater than the laboratory maximum dry density entered. That result should be checked carefully because sand calibration, hole volume, moisture content, recovered soil mass, material mismatch, or the selected maximum dry density can cause an unusually high value.
Which Proctor maximum dry density should I use?
Use the laboratory maximum dry density approved for the project material and compaction method. The field material should match the material represented by that laboratory result. If the project specifies a standard Proctor, modified Proctor, oversize correction, or agency-specific procedure, use the value accepted under that requirement.
When is the sand-cone method unsuitable for coarse soil?
The method has limits related to particle size, hole volume, and whether the excavated hole can hold a stable shape. Coarse material, sloughing sides, and oversized particles can make the volume measurement unreliable. Check the current ASTM method and project specifications before relying on the calculated density.