Bearing Capacity Definitions

• Bearing capacity: It is the loading capacity of the soil.
• Ultimate bearing capacity (qu): That is the least gross pressure that will result in the shear collapse of the supporting soil directly below the foundation.
• Net ultimate bearing power (qun): it is the net strain that can be added to the foundation by external loads that can only initiate the collapse of the underlying soil. That is equal to the ultimate carrying potential minus the stress due to the weight of the foundation an overload immediately above it. Assuming that density (concrete), and soil density (are similar enough to be treated equal, then

• Safe bearing capacity: This is the ability to hold after adding the factor of safety (FS). They are of two kinds,
• Net bearing capacity (qns): That is the net surface pressure that can be added to the soil in the event of shear failure. It is provided by the
• Safe gross capacity(qs): That is the highest gross pressure that the soil can bear safely without shear failure. It is given below,

• Allowable bearing pressure: It is the highest pressure of the soil deprived of any shear collapse or failure of settlement.

Techniques for Evaluating Bearing Capacity

1. Presumptive Analysis.
2. Analytical Methods.
3. Plate Bearing Test.
4. Penetration Test.
5. Modern Testing Methods.
6. Centrifuge Test.

Theory of Terzaghi's Bearing Capacity

• The depth of the foundation is less than or equal to the width of the foundation.
• The foundation base is coarse.
• The soil just above bottom of the foundation has little shear strength; it is just an overload it against overturning load.
• Surcharge up to the foundation base shall be considered.
• Load added is vertical and non-excentric.
• The soil is homogeneous and isotropic.
• The ratio of L/B is infinite.

1. Zone 1 is an aggressive Rankine zone. The active Rankine is at the angle of 45 + Ø/2
2. Zone 2 are the radial shear zones And form one set in the shear pattern. It zones release from outer edge of the centre of the base of the foundation.
3. Zone 3 is a passive zone. These are at 45 + Ø/2, the horizontal.

• Nc = (2Pc/Bc) + tan Ø
• Nq = (2pq/BγDf)
• Nγ = (4Pq/B2γ)

Bearing Capacity Failures

• General Shear Failure.
• Local Shear Failure.
• Punching Shear Failure.

1. General Shear Failure

2. Local Shear failure

• c’ = (2/3)c
• tanɸ’= (2/3) tanɸ’
• Nc‘, Nq‘, and Nγ‘ are the bearing capacity factors corresponding to ɸ’.

3. Punching Shear Failure

Types of Bearing Capacity Failures of Foundation

General Shear Failure

Local Shear Failure

Punching Shear Failure

Types of Shear Failure.

1. General Shear Failure.
2. Local Shear Failure.
3. Punching Shear Failure of foundation soils.

What Is Shear Failure?

What Are the Two Main Categories of Failures Described?

1. Failure due to loss of resources, and failure due to overload.
2. Failure due to social loafing and failure due to bad luck

Foundation Failure

1. Non-Functioning Windows and/or Doors.
2. Plumbing Damage or Disturbance.
3. Serious and Continuous Damage to the Framing.
4. Structure Risk.

Bearing Capacity

Terzaghi Bearing Capacity

Terzaghi Bearing Capacity Equation

Vesic Observed Types of Bearing Capacity Failures

• General Shear Failure: This type of failure occurs when the soil underneath a foundation shears and fails in a cohesive or non-cohesive soil. The failure surface is usually inclined at an angle of 30 to 45 degrees from the horizontal, and the bearing capacity is governed by the shear strength of the soil.
• Local Shear Failure: Local shear failure occurs in a cohesive soil when the stresses at the foundation's edge exceed the shear strength of the soil, causing it to fail. This type of failure typically occurs in relatively stiff soils, and the failure surface is usually inclined at an angle of 60 degrees or more from the horizontal.
• Punching Shear Failure: Punching shear failure occurs when a foundation, such as a footing or slab, presses down on a soil layer, causing it to fail in a cone-shaped surface. This type of failure typically occurs in non-cohesive soils and is governed by the soil's compressive strength.

Bearing Stress Which Would Cause Shear Failure in the Soil Below the Foundation

Types of Failure in Foundation

• General Shear Failure.
• Punching Shear Failure.
• Local Shear Failure.

Soil Bearing Capacity Failure

Failure of Footing

1. Settlement Failure
2. Overturning Failure
3. Sliding Failure
4. Bearing Capacity
5. Frost Heaving Failure

Load Bearing Capacity Definition

Bearing Power Theory

What Are the Typical Soil Failures?

• Shear Failure: Shear failure occurs when the soil underneath a foundation or slope fails due to shearing stresses exceeding the soil's shear strength. The failure surface is usually inclined at an angle of 30 to 45 degrees from the horizontal, and the bearing capacity is governed by the shear strength of the soil.
• Bearing Capacity Failure: Bearing capacity failure occurs when the soil underneath a foundation fails in shear, causing the foundation to sink into the soil. This type of failure can occur due to inadequate soil bearing capacity or an incorrect footing design.
• Slope Failure: Slope failure occurs when a slope's stability is compromised, causing the soil to slide or collapse. This type of failure can be caused by natural factors such as heavy rainfall, erosion, or seismic activity, or by human factors such as excavation or construction.
• Settlement Failure: Settlement failure occurs when the soil underneath a foundation compresses under the load of the structure, causing the foundation to settle and potentially leading to structural damage. Settlement failure can occur due to poor soil compaction, inadequate soil bearing capacity, or an incorrect footing design.
• Liquefaction: Liquefaction occurs when soil loses its strength due to an increase in pore water pressure during an earthquake or other seismic activity, causing it to behave like a liquid and potentially leading to settlement or slope failure.
• Expansive Soil Failure: Expansive soil failure occurs when soils that contain clay minerals expand and contract due to changes in moisture content, causing structural damage to foundations and other structures built on top of them.

Foundation Bearing

in General Shear Failure Continuous Failure Is Developed Between

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