Soil and rock change volume when excavated (loose state) and when compacted (fill state). Bulking and shrinkage factors are critical for haul truck sizing, fill quantity, and cut/fill balance calculations. Bank volume = in-situ; Loose volume = after excavation; Compacted volume = after placement and rolling.
Bulking Factors (Bank → Loose volume)
Loose volume = Bank volume × (1 + Bulking %)
| Soil Type | Bulking % | Shrink % | Loose Factor | Compact Factor | Note |
|---|
| Sand (dry) | 10–15% | 10–12% | 1.10–1.15 | 0.88–0.90 | Free-flowing, low bulking |
| Sand (moist) | 20–30% | 10–12% | 1.20–1.30 | 0.88–0.90 | Highest bulking — capillary water |
| Sand (wet/saturated) | 5–10% | 8–10% | 1.05–1.10 | 0.90–0.92 | Bulking collapses when fully wet |
| Loam / silty clay | 20–30% | 12–18% | 1.20–1.30 | 0.82–0.88 | Common in Indian construction |
| Stiff clay | 30–40% | 15–20% | 1.30–1.40 | 0.80–0.85 | — |
| Black cotton soil | 30–40% | 20–25% | 1.30–1.40 | 0.75–0.80 | Highest shrinkage — swelling clay |
| Gravel & sand mix | 10–20% | 8–12% | 1.10–1.20 | 0.88–0.92 | Good fill material |
| Well-graded gravel | 8–15% | 5–10% | 1.08–1.15 | 0.90–0.95 | Excellent fill |
| Hard murum / weathered rock | 30–40% | 10–15% | 1.30–1.40 | 0.85–0.90 | Common base course material |
| Soft rock (sandstone, shale) | 40–50% | 5–10% | 1.40–1.50 | 0.90–0.95 | Breakable by hand |
| Hard rock (granite, basalt — blasted) | 50–80% | 0–5% | 1.50–1.80 | 0.95–1.00 | Very high bulking; use as rip-rap |
| Concrete (broken/demolished) | 60–80% | 0% | 1.60–1.80 | 1.00 | Cannot be re-compacted to original |
Compaction Factors (Bank → Compacted)
Compacted volume / Bank volume — useful for fill quantity from cut
| Soil Type | Bulking % | Shrink % | Loose Factor | Compact Factor | Note |
|---|
| Sand | — | — | — | 0.88–0.92 | Standard Proctor compaction |
| Loam / silty clay | — | — | — | 0.82–0.88 | — |
| Heavy clay | — | — | — | 0.78–0.85 | — |
| Black cotton | — | — | — | 0.75–0.80 | — |
| Murum / GSB | — | — | — | 0.85–0.90 | Pavement subbase |
| Gravel-sand | — | — | — | 0.88–0.93 | — |
Quick Reference — Volume Relationships
| Soil Type | Bulking % | Shrink % | Loose Factor | Compact Factor | Note |
|---|
| Bank → Loose | — | — | Multiply by Loose Factor | — | Vloose = Vbank × LF |
| Loose → Bank | — | — | Divide by Loose Factor | — | Vbank = Vloose / LF |
| Bank → Compacted | — | — | — | Multiply by Compact Factor | Vcomp = Vbank × CF |
| Loose → Compacted | — | — | Divide by LF | Then × CF | Two steps |
| Cut volume needed for fill | — | — | — | Vfill / CF | How much to excavate |
| Truck loads from excavation | — | — | Vbank × LF / capacity | — | Truck volumes are loose |
Truck / Tipper Capacities (Indian)
| Soil Type | Bulking % | Shrink % | Loose Factor | Compact Factor | Note |
|---|
| 6-wheeler tipper | — | — | — | — | ≈ 6 m³ loose / 8–10 t |
| 10-wheeler tipper | — | — | — | — | ≈ 12–14 m³ loose / 16–18 t |
| 12-wheeler tipper | — | — | — | — | ≈ 16–20 m³ loose / 22–25 t |
| Tractor-trolley | — | — | — | — | ≈ 3 m³ loose / 4 t |
Notes
• Bulking and shrinkage are SITE-DEPENDENT — measure on the actual material whenever possible
• Sand bulking is highest at 4–6% moisture content; collapses to nothing when fully saturated
• Always tender on Bank (in-situ) volume — payment by truckload (loose) leads to disputes
• For black cotton and other expansive soils, allow extra cut for the high shrinkage on compaction
• Re-using excavated soil as fill: assume 80% recovery for clays, 90% for sandy soils
• Hard rock blasting can give 50–80% bulking — pre-plan disposal volume accordingly
• When importing fill, specify the source — laterite, river sand, and crusher dust have very different compaction behaviour
• For pavement subbase (GSB / WMM), aim for 95–98% MDD compaction (max dry density)
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