Bearing capacity failures
A bearing capacity failures are defined as foundation failure that occurs when a share stresses in soil exceed the shear strength of soil.Types of bearing capacity failures
- General shear failure
- Local shear Failure
- Punching shear failure
General shear failure
A strip footing resting on soft clay or on loose sand. The load-settlement curve is also shown in this figure, where s is the settlement and q is the load per unit area. The settlement increases suddenly at a certain load intensity equal to qu. In the soil, shear failure occurs at that load and the failure surface extend to the ground surface. This type of failure is called general shear failure. In general shear failure, a heave on the sides is always observed.
Local Shear failure-
A strip footing resting on clay of medium consistency or on medium dense sand. The load-settlement curve is aslo shown in this figure. The foundation movement is accompanied by sudden jerks when the load is equal to a certain value qu(1). The failure surfaes gradually extend outwards from the foundation, as shown. However, for the failure surfaces, a considerable movement of the foundation is needed, to extend to the ground surface. The load at which this happens is equal to qu. After that point, an increase in law is accompanied by a large increase in settlement. These type of failures are known as a local shear failure. When there is substantial vertical then only heave is observed.
Punching shear failure
A strip footing resting on soft clay or on loose sand. The failure surfaces do not extend up to the ground surface in this case. There jerks in the foundation at a load of qu(1). At a load of qu the footing fails and at this stage, the load-settlement curve becomes steep and practical linear. This type of failure is known as punching shear failure. We have observed and more here is an only vertical movement of footing.