Sometimes, on soft soil sites, large settlements may occur under loaded foundations without actual shear failure occurring; in such cases, the allowable bearing capacity is based on the maximum allowable settlement.
The ultimate bearing capacity, on the other hand, is the maximum pressure that can be applied to the soil before it fails.
It depends upon the shear strength of soil as well as shape, size, depth and type of foundation.
A foundation is a connecting link between the structure proper and the ground which supports it.
The bearing strength characteristics of foundation soil are major design criterion for civil engineering structures.
Sometimes, on soft soil sites, large settlements may occur under loaded foundations without actual shear failure occurring; in such cases, the allowable bearing capacity is based on the maximum allowable settlement.
[1] A general bearing failure occurs when the load on the footing causes large movement of the soil on a shear failure surface which extends away from the footing and up to the soil surface.
The basic method was developed by Terzaghi, with modifications and additional factors by Meyerhof and Vesić.
Prevention against other failure modes is accounted for implicitly in settlement calculations.
[2] Stress distribution in elastic soils under foundations was found in a closed form by Ludwig Föppl (1941) and Gerhard Schubert (1942).
Karl von Terzaghi was the first to present a comprehensive theory for the evaluation of the ultimate bearing capacity of rough shallow foundations.
This theory states that a foundation is shallow if its depth is less than or equal to its width.
[4] Terzaghi developed a method for determining bearing capacity for the general shear failure case in 1943.
[4] In 1951, Meyerhof published a bearing capacity theory which could be applied to rough shallow and deep foundations.
[6] Meyerhof (1951, 1963) proposed a bearing-capacity equation similar to that of Terzaghi's but included a shape factor s-q with the depth term Nq.