52
Shallow Foundations: Bearing Capacity and Settlement 1.0
500
0.8
250 50
λγc = λqc
0.6 5 2.5
0.4
10
100
25
Ir = 1 0.2
0
0
20 40 Soil friction angle, φ (deg)
50
Figure 2.23 Variation of lgc = l qc with f and Ir for foundation with L/B > 5.
Example 2.2 Refer to Example 2.1a. For the soil, given: modulus of elasticity E = 620 kN/m2; Poisson’s ratio n = 0.3. Considering the compressibility factors, determine the ultimate bearing capacity.
Solution
Ir =
620 G E = 4.5 = = c + q tan φ 2(1 + ν )(c + q tan φ ) 2(1 + 0.3)[48 + (18 × 0.6) tan 25]
From equation (2.85):
I r ( cr ) =
=
φ 1 B exp 3.3 - 0.45 cot 45 - 2 L 2 1 0.6 25 exp 3.3 - 0.45 × cot 45 - 2 = 62.46 2 1 . 2