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Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
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Punching shear may occur in loose sand with density less than _______
45%
50%
35%
20%
35%
Punching shear failure occurs in soil foundations when the soil is very loose, leading to a vertical shearing of the soil directly beneath the footing without significant bulging or soil deformation ┬╖ This behavior is primarily observed in loose sand with a relative density (DrтАЛ) of less than 35%.
Punching shear failure occurs in soil foundations when the soil is very loose, leading to a vertical shearing of the soil directly beneath the footing without significant bulging or soil deformation ┬╖ This behavior is primarily observed in loose sand with a relative density (DrтАЛ) of less than 35%.
DrтАЛ=emaxтАЛтИТeminтАЛemaxтАЛтИТeтАЛ├Ч100
DrтАЛ<35% тАФ Condition for Punching Shear
As the footing load is applied to loose sand, the soil beneath the base compresses vertically ┬╖ Because the density is too low for the soil particles to interlock or develop a clear failure surface (unlike general shear failure), the footing 'punches' through the soil matrix ┬╖ This results in significant settlement without the typical rotational failure mechanism found in dense soils.
Punching shear failure is characterized by high settlement and low bearing capacity.
It is common in soft clays and loose sands with relative density below 35%.
General shear failure usually occurs in dense sands (DrтАЛ>70%).
Local shear failure occurs in medium dense sands (35%<DrтАЛ<70%).
Predictable settlement behavior in very loose soils
Allows for ground improvement design (e.g., compaction)
Extremely low bearing capacity of soil
Potential for sudden excessive settlement under heavy loads
Foundation design in alluvial deposits
Assessment of reclaimed land stability
Relative Density (DrтАЛ) measures the compactness of cohesionless soil.
The range of DrтАЛ from 35% to 70% is generally associated with local shear failure.
Options A, B, and D are incorrect as they fall outside the specific empirical range defined for punching shear.
C is correct тАФ Punching shear failure is specifically associated with loose sandy soils having a relative density of less than 35%.
Always remember the classification: DrтАЛ<35% (Punching), 35%<DrтАЛ<70% (Local), and DrтАЛ>70% (General Shear) for sandy soils.