State of Equilibrium in Bearing Capacity Failures

In bearing capacity failures, the state of equilibrium refers to the condition where the applied load is balanced by the resistance provided by the soil. The state of equilibrium is fully developed when the failure mechanism reaches its ultimate limit. Among the different types of bearing capacity failures, it is the general shear failure that fully develops the state of equilibrium.

Local Shear Failure
- Local shear failure occurs when the soil fails along a small surface area beneath the foundation.
- This type of failure can happen when the applied load exceeds the shear strength of the soil in a localized region.
- In local shear failure, the state of equilibrium is not fully developed as the failure occurs at a small scale rather than involving the entire failure surface.

Punching Shear Failure
- Punching shear failure occurs when a concentrated load is applied to a relatively thin slab or footing.
- This type of failure is characterized by the formation of a cone-shaped or funnel-shaped failure surface beneath the load.
- Similar to local shear failure, the state of equilibrium is not fully developed in punching shear failure as the failure occurs in a localized manner.

General Shear Failure
- General shear failure, also known as base shear failure, occurs when the soil fails in a large, general failure surface beneath the foundation.
- This type of failure is characterized by a relatively flat failure surface that extends beyond the foundation footprint.
- In general shear failure, the state of equilibrium is fully developed as the failure mechanism involves the entire failure surface, resulting in a balanced condition between the applied load and the soil resistance.

Conclusion
Among the different bearing capacity failures, it is the general shear failure that fully develops the state of equilibrium. In local shear failure and punching shear failure, the failure occurs in a localized manner, and the state of equilibrium is not fully reached. Therefore, option B - general shear failure, is the correct answer.