settlement_of_shallow_foundations_on_granular_soils (Lutenegger ang DeGroot)

thus underestimate settlement. A comparison between the Fox (1948) and Burland (1970) charts for
a circular area is shown in Figure 4.10. Christian and Carrier (1978) suggested that Burland's (1970)
embedment correction factors be used with Giraud's (1972) depth factors as shown in Figure 4.11
but also noted that "ignoring embedment all together is nearly as good a procedure and may be the
best approach when other effects .... are to be considered". Christian and Carrier (1989) restated
their position in a discussion to Bowles (1987).
Other factors have been suggested to account for embedment of the foundation, e.g.,
Yamaguchi (1984), however, the factors presented by Fox, Janbu or Burland appear to be more
often used in practice.
4.2 Tschebotarioff (1953, 1971)
Tschebotarioff (1953, 1971) suggested a simplified method of settlement analysis useful for
footings resting on sands and other cohesionless soils. The method, as applied to square footings,
assumes that the surface load is carried within the soil mass by a truncated pyramid of soil. The
surface settlement is equal to the compression of the entire pyramid of height H. The total
compression is the sum of the compressive strains of all of the successive horizontal layers dH of
the pyramid. Each of the successive layers occupies a horizontal area A= (b + 2H tano:) 2 , where o:
is defined as shown in Figure 4.12. For an assumed value of o: = 30', the settlement is given as:
s = (0.867 qbC,)IE
[4.4]
where:
q = applied footing stress
b = footing width
C, = layer thickness correction factor
E = Young's Modulus
The correction factor C, is to account for values of H less than infinity. Values of c; for various
values ofH/b are shown in Figure 4.13. For an infinity long strip footing of width b, the settlement
may be obtained in a similar manner foro:= 30" as:
s = [(2.0qb)/ E]log [1 + (1.154H)/b] [4.5]
4.3 Canadian Foundation Manual (1975, 1985, 1992)
The Canadian Foundation Manual (CFM) suggests that settlement estimates of footings may
be made by dividing the soil into layers, calculating the value of the applied stress at the midpoint
of each layer and using an apparent modulus of elasticity of the soil layer to determine the
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