Shear failure
Introduction
In geotechnical engineering, the capacity of the terrain "Soil (engineering)") to withstand the loads applied to it is called bearing capacity. Technically, the bearing capacity is the maximum average contact pressure between the foundation and the ground such that failure due to soil shear or excessive differential settlement does not occur. Therefore, the allowable bearing capacity must be based on one of the following functional criteria:.
The ultimate bearing capacity is the maximum pressure that the soil can withstand before failure without considering settlements. There are three types of possible failure, these are general shear failure, local shear failure and punching failure. The type will depend on the soil and its resistant characteristics, as well as the characteristics of the foundation, mainly its depth and dimensions.[1].
Similarly, the expression bearing capacity is used in other branches of engineering to refer to the capacity of a structure to withstand the loads applied to it.
Short and long term load capacity
The mechanical properties of a soil usually differ under loads that vary (almost) instantaneously and quasi-permanent loads. This is because soils are porous, and these pores can be fully or partially saturated with water. In general, soils behave more rigidly in the face of changing loads almost instantaneously since these increase the interstitial pressure, without producing the dislocation of an appreciable amount of water. On the other hand, under permanent loads the difference in pore pressure between different parts of the land produces drainage of some areas.
When calculating or verifying the bearing capacity of a land on which there is a construction, the short term (case without drainage) and the long term (with drainage) must be taken into account. In the short-term behavior, all terms except ultimate cohesion are neglected, while in the long-term bearing capacity (case with drainage) the internal friction of the ground and its specific weight are also important.