In geotechnical engineering, understanding the factors contributing to foundation failures is crucial for ensuring the stability and safety of structures. One common scenario that engineers encounter is a base failure, where the shear strength of the soil surpasses its bearing capability. This blog, curated by Sathvik, one of the best builders in Velachery, will explore soil-bearing capacity failures.
What Does Soil-Bearing Capacity Mean?
The term soil-bearing capacity denotes the soil’s capability to endure the loads. The crucial factors are the shear strength and density of the soil. The load depth also plays a significant role in determining bearing capacity: the greater the embedding depth, the greater the load-bearing strength. The soil’s bearing capacity represents the load’s maximum ability to endure without displacement. Calculating the capacity of safe bearing involves dividing the soil’s bearing capacity by its safety factor.
General Shear Failure:
General shear failure occurs when the shear stress at the base of a foundation exceeds the soil’s shear strength. In this condition, the underlying soil is ruptured, along with the soil bulging near the footing. Hence, as a result, soil on the side heaves up, making the structure tilt.
What distinguishes general shear failure is its occurrence at a relatively low strain. The entire soil mass within the failure wedge participates in the failure, leading to a well-defined failure surface. This failure is further marked by significant bulging of the sheared soil bulk. Sidewall heaving is a common observation, and the continuous bulging near the footing is accompanied by tilting.
Local Shear Failure:
Local shear failure is another type of bearing capacity failure that occurs when the shear stress at specific points on the foundation exceeds the local shear strength. Unlike general shear failure, the failure surface in local shear failure is limited to specific localized zones within the soil mass.
One classic example of local shear failure is observed in strip footings on loose sand or soft clay. The settlement abruptly increases, leading to shear failure in the soil at a particular load intensity. The failure of the ground surface extends, heaving on the sidewalls with shear mass bulging near the footing with increased structure tilting.
Punching Shear Failure:
Punching shear failure is typically associated with structures such as slabs or footings subjected to concentrated loads. This type of failure occurs when the applied load causes shear stresses that exceed the soil’s shear strength beneath the loaded area. The failure is characterized by forming a cone-shaped failure surface extending from the loaded point to the base.
During the design phase of any construction project, it is essential to assess the inherent load-bearing capacity of the soil. Whether the load emanates from a building foundation, crane, or retaining wall, the ground must adequately withstand it without undergoing significant settlement or collapse. Understanding the various bearing capacity failures is imperative before structuring the project to prevent future failures. Approach Sathvik, one of the best house construction companies in Chennai, to implement effective design and mitigation strategies by recognizing the specific characteristics and contributing factors of each type of failure, ensuring the stability and longevity of structures built on varying soil conditions.
