Geotechnical Engineering

DHARM

BEARING CAPACITY 547

Table 14.2 Schleicher’s shape coefficients or influence factors (Jumikis, 1962)

Shape of Side ratio Center point Free corner Mid-point Mid-point K (average)

bearing area a/b M, Kmax point A, Kmin of short side of long side

= KM = KA B, KB C, KC

C

A B

M

a

b

Circle — 1.13 0.72 0.72 0.72 0.96

Square 1.0 1.12 0.56 0.76 0.76 0.95

Rectangle 1.5 1.11 0.55 0.73 0.79 0.94

Rectangle 2 1.08 0.54 0.69 0.79 0.92

Rectangle 3 1.03 0.51 0.64 0.78 0.88

Rectangle 5 0.94 0.47 0.57 0.75 0.82

Rectangle 10 0.80 0.40 0.47 0.67 0.71

Rectangle 100 0.40 0.20 0.22 0.36 0.37

Rectangle 1000 0.173 0.087 0.093 0.159 0.163

Rectangle 10000 0.069 0.035 0.037 0.065 0.066

If, in the Schleicher’s equation 14.2 above, the tolerable settlement, s, the shape coeffi-

cient K, the size A of the loading area and the soil properties included under C, are known, the

bearing capacity q can be calculated as,

q =

sC

KA

.

. ...(Eq. 14.3)
The elastic settlement equation also permits deriving the following rule:
s
s

1

2

=

A

A

1

2

...(Eq. 14.4)

where s 1 and s 2 are settlements brought about by two bearing areas of similar shape but of
different sizes, A 1 and A 2 respectively, with equal contact pressures.
This rule, expressing a model law, is useful in calculating the settlement of a prototype
foundation, if the settlement attained by a model with the same contact pressure has been
measured.

14.5.2 The Classical Earth Pressure Theory—Rankine’s, Pauker’s, and Bell’s

Methods

The classical earth pressure theory assumes that on exceeding a certain stress condition, rup-

ture surfaces are formed in the soil mass. The stress developed upon the formation of the

rupture surfaces is treated as the ultimate bearing capacity of the soil.