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Questions and Answers
What is the primary distinction between local and general shear failure in shallow foundations?
What is the primary distinction between local and general shear failure in shallow foundations?
- Local shear failure affects only a small area around the footing. (correct)
- Local shear failure results in tilting, while general shear maintains footing level.
- General shear failure is always associated with excessive settlement.
- General shear failure occurs only in cohesive soils.
Which method is NOT typically associated with determining the bearing capacity of granular soils?
Which method is NOT typically associated with determining the bearing capacity of granular soils?
- Rankine's theory (correct)
- Terzaghi’s method
- Static cone penetrometer test
- Meyerhof’s method
The concept of a raft foundation is best described as which of the following?
The concept of a raft foundation is best described as which of the following?
- A large concrete slab that distributes load over a wide area. (correct)
- A deep foundation type that extends below the water table.
- A foundation that is unsupported and floating on soft soil.
- A foundation that relies solely on skin friction with the soil.
Which in-situ test is specifically designed to measure the bearing capacity of soil directly beneath a footing?
Which in-situ test is specifically designed to measure the bearing capacity of soil directly beneath a footing?
What is the primary purpose of a contact pressure distribution diagram beneath a footing?
What is the primary purpose of a contact pressure distribution diagram beneath a footing?
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Study Notes
Bearing Capacity of Shallow Foundation
- Local Shear Failure: Soil directly beneath the foundation yields and the failure zone is localized.
- General Shear Failure: Failure zone extends outward from the foundation, causing a wider area of soil to yield.
- Terzaghi's Bearing Capacity Theory: A classical approach that calculates bearing capacity based on soil cohesion, friction angle, and foundation width and depth.
- Skempton's Bearing Capacity Theory: Focuses on the influence of the foundation shape and depth on the bearing capacity.
- Meyerhof's Bearing Capacity Theory: Refines Terzaghi's theory by incorporating factors for various foundation shapes and soil conditions.
- BIS Method for Bearing Capacity: Indian Standard Code specifies bearing capacity based on soil properties and foundation geometry, includes safety factors.
- Bearing Capacity of Granular Soils using SPT Value: The Standard Penetration Test (SPT) provides an in-situ assessment of the soil's resistance. Empirical correlations allow for estimating the bearing capacity using SPT N-values and soil properties.
- Raft Foundation: A wide, rigid foundation that distributes the load over a large area, often used for heavy structures or poor soil conditions.
- Floating Foundation: A foundation that rests on the soil's buoyant force, typically used where the soil is weak or compressible.
- Plate Load Test: A direct in-situ method that involves applying a controlled load to a plate resting on soil and measuring the settlement, provides accurate bearing capacity for the specific location.
- Static Cone Penetrometer (CPT): A device pushed into the soil to measure resistance, allows for assessing soil strength and bearing capacity at various depths.
- Pressure Meter Test (PMT): An in-situ test that measures the soil's deformation under pressure, resulting in estimations of its strength and bearing capacity.
- Contact Pressure Distribution Diagram: A graphical representation of the pressure distribution beneath the base of a footing, typically exhibiting a non-uniform distribution due to the soil's response to the load.
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