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In an assumption made in the Bligh's Creep Theory for design of impervious floor for sub surface flow, the hydraulic gradient
  • a)
    increases throughout the impervious length of the apron
  • b)
    decreases from upstream side to downstream side of the structure
  • c)
    is always zero only in the middle of the impervious length of the apron
  • d)
    is constant throughout the impervious length of the apron
Correct answer is option 'D'. Can you explain this answer?
Most Upvoted Answer
In an assumption made in the Blighs Creep Theory for design of impervi...
Bligh's Creep Theory and Impervious Floors

Bligh's Creep Theory is a method used in the design of impervious floors for sub-surface flow. The theory is based on the assumption that the soil particles just below the impervious layer creep slowly under load. This causes a hydraulic gradient that can be calculated using certain assumptions.

Hydraulic Gradient

The hydraulic gradient is defined as the change in hydraulic head per unit distance along the flow path. It is a measure of the pressure difference that drives the flow of water through the soil. In the case of an impervious floor, the hydraulic gradient is assumed to be constant throughout the impervious length of the apron.

Assumption of Constant Hydraulic Gradient

The assumption of a constant hydraulic gradient throughout the impervious length of the apron is based on the fact that the soil particles just below the impervious layer are assumed to be in a state of equilibrium. This means that they are not moving and there is no net flow of water through the soil.

This assumption is valid only if the hydraulic gradient is constant. If the gradient were to change, then there would be a net flow of water through the soil, which would cause the soil particles to move and the hydraulic gradient to change again. This would result in a cyclical process of soil movement and hydraulic gradient change, which is not desirable.

Conclusion

In conclusion, the correct answer to the question is option 'D', which states that the hydraulic gradient is constant throughout the impervious length of the apron. This assumption is based on the fact that the soil particles just below the impervious layer are assumed to be in a state of equilibrium and not moving. A constant hydraulic gradient ensures that there is no net flow of water through the soil and prevents the cyclical process of soil movement and hydraulic gradient change.
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In an assumption made in the Blighs Creep Theory for design of impervi...
Bligh’s Creep Theory:
  • Bligh assumed that the percolating water follows the outline of the base of the structure which is in contact with the subsoil.
  • The length of the path traversed by the percolating water is called the length of creep or creep length.
  • He further assumed that the head loss per unit length of creep (i.e. H/L) which is called hydraulic gradient is constant throughout the percolating passage i.e. Loss of head is proportional to length of the creep.
Hydraulic Gradient (i) = 
The reciprocal of hydraulic gradient (i.e. L/H) is known as Bligh’s Coefficient of creep.
Additional Information
Percolation Coefficient:
It is defined as the ratio of coefficient of permeability to porosity of soil.

Where,
K = co-efficient of Permeability
η = Porosity.
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In an assumption made in the Blighs Creep Theory for design of impervious floor for sub surface flow, the hydraulic gradienta)increases throughout the impervious length of the apronb)decreases from upstream side to downstream side of the structurec)is always zero only in the middle of the impervious length of the aprond)is constant throughout the impervious length of the apronCorrect answer is option 'D'. Can you explain this answer?
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In an assumption made in the Blighs Creep Theory for design of impervious floor for sub surface flow, the hydraulic gradienta)increases throughout the impervious length of the apronb)decreases from upstream side to downstream side of the structurec)is always zero only in the middle of the impervious length of the aprond)is constant throughout the impervious length of the apronCorrect answer is option 'D'. Can you explain this answer? for Civil Engineering (CE) 2024 is part of Civil Engineering (CE) preparation. The Question and answers have been prepared according to the Civil Engineering (CE) exam syllabus. Information about In an assumption made in the Blighs Creep Theory for design of impervious floor for sub surface flow, the hydraulic gradienta)increases throughout the impervious length of the apronb)decreases from upstream side to downstream side of the structurec)is always zero only in the middle of the impervious length of the aprond)is constant throughout the impervious length of the apronCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Civil Engineering (CE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for In an assumption made in the Blighs Creep Theory for design of impervious floor for sub surface flow, the hydraulic gradienta)increases throughout the impervious length of the apronb)decreases from upstream side to downstream side of the structurec)is always zero only in the middle of the impervious length of the aprond)is constant throughout the impervious length of the apronCorrect answer is option 'D'. Can you explain this answer?.
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