Field Density Test Report
[ Method: Sand Replacement (IS 2720 Part-28) ]
| Parameter | Sample 1 | Sample 2 | Sample 3 |
|---|---|---|---|
| MDD (gm/cc) | |||
| Bulk Density Sand | |||
| Offset / Chainage | |||
| FIELD DATA | |||
| Wt. Wet Material (Ww) gm | |||
| Sand+Cyl Before (W1) gm | |||
| Sand+Cyl After (W2) gm | |||
| Sand in Cone (W3) gm | |||
| Sand in Hole (W4) gm | |||
| Volume Hole (V) cc | |||
| Bulk Density (Yb) gm/cc | |||
| MOISTURE CONTENT | |||
| Field Moisture Content (%) | |||
| RESULTS | |||
| Field Dry Density (Yd) gm/cc | |||
| Compaction % | |||
Technical Guide: Field Density Test (Sand Replacement Method)
While the Core Cutter method is ideal for cohesive, soft soils, it fails entirely when the earthwork contains gravel, hard stones, or mixed granular materials (like GSB layers). For these harder strata, civil engineers strictly rely on the Sand Replacement Method to verify in-situ compaction.
1. The Core Principle (IS 2720 Part 28)
The Solution: You fill that irregular hole with standard, uniform sand of a known density. By measuring how much sand it took to fill the hole, you can mathematically reverse-calculate the exact volume of the hole.
2. The Three Critical Weights
To accurately determine the volume of the hole, the test requires three physical weighments using a standard Sand Pouring Cylinder:
- W1 (Initial Weight): The total weight of the cylinder completely filled with standard sand before the test begins.
- W2 (Final Weight): The weight of the cylinder and the remaining sand after filling the excavated hole and the conical funnel.
- W3 (Cone Weight): The standard weight of the sand required to fill just the conical funnel portion of the apparatus. This must be calibrated in the lab beforehand.
3. The Engineering Calculations
Our automation tool processes these weights instantly using the following IS code formulas:
- Weight of Sand in Hole (W4): W1 - W2 - W3
(This isolates the sand sitting purely inside the excavated hole). - Volume of Hole (V): W4 / Bulk Density of Standard Sand
(Weight divided by Density equals Volume). - Bulk Density of Soil (Yb): Wet Weight of Excavated Soil (Ww) / Volume of Hole (V)
- Dry Density of Soil (Yd): Yb / [1 + (Moisture Content % / 100)]
- Percentage of Compaction: (Field Dry Density / Laboratory MDD) × 100
4. Acceptance Criteria & Statistical Quality Control
In modern highway engineering (as per MORTH guidelines), simply passing a single test is not enough. The compaction is evaluated statistically across a block of tests. A set of tests is only accepted if the statistical Mean Density meets the specific variance threshold calculated using Standard Deviation (SD).
This automated calculator instantly computes the Average Compaction, Standard Deviation, and verifies the final Acceptance Limit, allowing TPI engineers to instantly approve or reject the compacted layer on site.