Explanation:

• Ultimate bearing capacity (q_u): The maximum applied gross pressure at base of foundation without shear failure.
• Net ultimate bearing capacity (q_nu): Overburden pressure is neglected from ultimate bearing capacity.

                            q_nu = q_u - Î³D_f 

• Ultimate gross bearing capacity (q_gross): Sum of ultimate net bearing capacity and overburden pressure above footing base.
• Net safe bearing capacity (q_ns): Net ultimate bearing capacity is divide by certain factor of safety.

                               q_u = $\frac{qnu}{FOS}$

FOS is ratio of ultimate net bearing capacity to allowable net bearing capacity.

• Safe bearing capacity (q_safe): It is provided margin of safety against foundation collapse from shear failure. 

q_safe = $\frac{qnu}{FOS}$+ Î³D_f 

Based partly on ory and partly on laboratory test, Skempton observed that factor Nc increases with ratio D/B.

According to Rankine?s equation bearing capacity of cohesion less soil is zero at ground surface.

M Meyerhof?s extended analysis of plastic equilibrium of a surface footing to Shallow and Deep foundation according to both Terzaghi and Meyerhof analysis.

Indian standard recommends that standard penetration resistance is determined at a number of selected points at intervals of 75 cm in vertical direction or change of strata if it takes place earlier.

The penetration test are useful for general exploration of erratic soil profiles, for finding depth to bed rock or hard stratum, and to have an approximation indication of strength and or properties of soils.

Terzaghi assumed value of angle ? = ?, which is not true. Since footings are normally rough, ? has been found close to 45° + ?/2 than to ?, thus Terzaghi?s bearing capacity equations do not have provision for including depth effects, inclination factors, etc.

In order to determine safe bearing capacity, it would be normally sufficient to use a factor of safety of 2 or 2.5 on ultimate bearing capacity.

The effect of settlement upon structure depends on its magnitude, length of time over which it takes place, its magnitude and nature of structure itself.

In local shear failure re is a significant compression of soil under footing and only partial development of state of plastic equilibrium. Due to this reason, failure surface does not reach ground.