SOIL AND EARTHWORK FORMULAS 187

(8.6)

(8.7)

(8.8)

Unit weights are generally expressed in pound per cubic foot or gram per cubic
centimeter. Representative values of unit weights for a soil with a specific grav-
ity of 2.73 and a void ratio of 0.80 are

(8.9)

(8.10)

(8.11)

The symbols used in the three preceding equations and in Fig. 8.1 are

Gspecific gravity of soil solids (specific gravity of quartz is 2.67; for

majority of soils specific gravityranges between 2.65 and 2.85; organic

soils would have lower specific gravities)

 0 unit weight of water, 62.4 lb/ft^3 (1.0 g/cm^3 )

evoids ratio, volume of voids in mass of soil dividedby volume of solids

in same mass; also equal to n/(1n), where nis porosity—volume of

voids in mass of soil divided by total volume of same mass

Sdegree of saturation, volume of water in mass of soil divided by volume

of voids in same mass

wwater content, weight of water in mass of soil divided by weight of

solids in same mass; also equal to Se/G

b60 lb/ft^3 0.96 g/cm^3

dry95 lb/ft^3 1.52 g/cm^3

sat122 lb/ft^3 1.96 g/cm^3

b

(G1) 0

1 e

S100%

dry

G 0

(1e)

S0%

sat

(Ge) 0

1 e



(1w)G 0

1 e

S100%

Total volume (solids + water + gas) = 1

Gas

Water

(^1) Solids

1 +
e
V
(solids)
W
(total) (for unit
V
) =
γf
V
= 1
V
(voids)
V
(water)
W
(water)
W
(solids)
e

1 +
e
Se

1 +
e
1
G
γ^0
γ^0

1 +
e
G

• 
  

  Se
  γ^0

  
  

  1 +
  e
  1 +
  w
  G
  γ^0

  
  

  1 +
  e
  Se

  
  

  1 +
  e
  FIGURE 8.1 Relationship of weights and volumes in soil.