Soil and Rock Bulking Factors

Soil or rock expansion - swell - after mining

One cubic of soil or rock at the borrow expands and does not translate into one cubic of fill in the lorry, stockpiled or placed and compacted on the site.

soil - from borrow to lorry

Bulking or Swell factors for some common materials are indicated below:

Material Density at the Borrow
103
(kg/m3)
Bulking (Swell) Factor
(%)
Basalt 2.4 - 3.1 75 - 80
Clay 1.8 - 2.6 20 - 40
Dolomite 2.8 50 - 60
Earth 20 - 30
Gneiss 2.69 75 - 80
Granite 2.6 - 2.8 75 - 80
Gravel, dry 1.80 20 - 30
Gravel, wet 2.00 20 - 30
Gravel, wet w/clay 50 - 60
Limestone 2.7 -2.8 75 - 80
Loam 15 - 25
Quartz 2.65 75 - 80
Rock 40 - 80
Sand, dry 1.60 20 - 30
Sand, wet 1.95 20 - 30
Sandstone 2.1 - 2.4 75 - 80
Slate 2.6 - 3.3 85 - 90
Soil 1.2 - 1.6 20 - 30
  • 1 kg/m3 = 0.001 g/cm3 = 0.0005780 oz/in3 = 0.16036 oz/gal (Imperial) = 0.1335 oz/gal (U.S.) = 0.0624 lb/ft3 = 0.000036127 lb/in3 = 1.6856 lb/yd3 = 0.010022 lb/gal (Imperial) = 0.008345 lb/gal (U.S) = 0.0007525 ton/yd3

Example - Swell Factor

After excavation 300 m3 with bulking factor 40% swells to

300 (m3) (100% + 40%) / 100% = 420 m3 

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