Civil Engineering Reference
In-Depth Information
FIGURE 8.2
Punching shear foundation failure. (
After Vesic 1963.
)
analysis, the factor of safety is often in the range of 5 to 10 (Krinitzsky et al. 1993). These
are high factors of safety compared to other factors of safety, such as only 1.5 for slope sta-
bility analyses (Chap. 9).
4.
Minimum footing sizes:
Building codes often require minimum footing sizes and
embedment depths. Larger footing sizes will lower the bearing pressure on the soil and
reduce the potential for static or seismic bearing capacity failures.
5.
Allowable bearing pressures:
In addition, building codes often have maximum
allowable bearing pressures for different soil and rock conditions. Table 8.2 presents maxi-
mum allowable bearing pressures based on the
Uniform Building Code
(Table 18-I-A, 1997).
Especially in the case of dense or stiff soils, these allowable bearing pressures often have ade-
quate factors of safety for both static and seismic cases.
