Geotechnical Engineering

DHARM

BEARING CAPACITY 577

where S = settlement of the proposed foundation (mm),

S (same units)

p = settlement of the test plate (mm),

b = size of the proposed foundation (m), and

bp = size of the test plate (m).

This is applicable for sands.

However, the relationship is simpler for clays, since the modulus value Es, for clays is

reasonably constant:

S

Sp

=

b

bp

...(Eq. 14.111)

Equation 14.110 may be put in a slightly simplified form as follows:

S = Sp

2

03

2

b

b+

L

N

M

O
Q
.P ...(Eq. 14.112)
where Sp = Settlement of a test plate of 300 mm square size,
and S = Settlement of a footing of width b.
The method for the determination of the bearing capacity of a footing of width b should
be apparent now. The permissible settlement value, such as 25 mm, should be substituted in
the equation that is applicable (Eq. 14.110 to 14.112) ; and the Sp, the settlement of the plate
must be calculated. From the load-settlement curve, the pressure corresponding to the com-
puted settlement Sp, is the required value of the ultimate bearing capacity, qult, for the footing.

14.9.2Abbet’s Improved Method of Plotting

Abbet recommends an improved method of plotting the results of the plate load test which is

shown in Fig. 14.17.

0.1 0.2 0.3 0.4 0.5 6 7 8 9 1 2 3 4 5 6 7 8 9 18 20 30 40 50 6070 8090100

1000

900

800

700

600

500

400

300

200

100

80

70

60

50

40

30

20

10

90

Pressure kN/m (Log scale)

2

Elastic zone Plastic zone

Settlement (mm) (Log scale)

Fig. 14.17 Improved method of plotting of plate load test results (After Abbet)

O

QP