Test Method Statements
Field Density Test (FDT) – Sand Cone Method
Checking compaction of backfill and sub-base layers against the lab maximum dry density.
Reference standards: ASTM D1556, ASTM D1557 (Modified Proctor)
Equipment
- Sand cone apparatus & calibrated sand
- Base plate
- Digging tools
- Scale
- Moisture tins / oven or speedy moisture tester
Procedure
- Get MDD and OMC for the fill material by Modified Proctor test.
- Level the compacted layer surface and seat the base plate.
- Dig a hole about 150 mm deep through the plate; save all soil in a sealed container.
- Weigh the soil and determine its moisture content.
- Pour calibrated sand into the hole through the cone; weigh the sand used to find hole volume.
- Dry density = (wet mass ÷ volume) ÷ (1 + w). Compaction % = field dry density ÷ MDD × 100.
Acceptance criteria
- Usually ≥ 95% MDD for structural fill and ≥ 98% for road sub-base (follow project spec).
- One test per 500 m² per layer or as specified; layers ≤ 200–250 mm loose.
Health & safety
- Wear PPE: helmet, safety shoes, gloves and eye protection.
FAQs
What is the Field Density Test (FDT) – Sand Cone Method used for?
Checking compaction of backfill and sub-base layers against the lab maximum dry density.
Which standard does it follow?
It is based on ASTM D1556, ASTM D1557 (Modified Proctor). Always follow your project specification where it differs.
Can I print or submit this?
Yes. Use Print / PDF, add your project details and submit it through your normal approval process. Get it reviewed by your engineer or consultant first.
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General guidance only, not engineering advice. Project specifications, approved drawings, manufacturer data sheets and your consultant's instructions take priority. See our Policy. This document was generated using CM PRO. Powered by CM PRO.