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Precast concrete pile of size 50 cm × 50 cm is to be driven into clay strata. The unconfined compressive strength of which is 110 kN/m2. Then the length required to carry a safe working load of 500 kN with FOS = 3 and α = 0.6 is _______ m.
  • a)
    18
  • b)
    21
  • c)
    23
  • d)
    17
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
Precast concrete pile of size 50 cm × 50 cm is to be driven into clay...
Soil is clay ≡ point bearing
Qu = CubNcAb + aCu avAs
Qu = 500 × FOS = 500×3 = 1500
1500 = 110/2 × 9 × 0.52 + 0.6 × 110/2 × 4 × 0.5 × L
L = 20.8522 m.
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Most Upvoted Answer
Precast concrete pile of size 50 cm × 50 cm is to be driven into clay...
Given data:
Size of precast concrete pile = 50 cm × 50 cm
Unconfined compressive strength of clay strata = 110 kN/m²
Safe working load = 500 kN
FOS = 3
α = 0.6

To find: Length required to carry the safe working load

Solution:
1. Calculate the ultimate bearing capacity of the clay strata:
qult = C × Nc + γDf × Nq + 0.5 × γB × B × Nγ
where,
C = Unconfined compressive strength of clay strata = 110 kN/m²
γ = Unit weight of soil = 18 kN/m³ (assumed)
Df = Depth factor = 1 (for depth less than 3 times the width of pile)
B = Width of pile = 0.5 m
Nc, Nq, Nγ = Bearing capacity factors (values can be obtained from standard tables)
For clay,
Nc = 5.7, Nq = 1, Nγ = 0
qult = 110 × 5.7 + 18 × 1 × 1 + 0.5 × 18 × 0.5 × 0
qult = 672.6 kN/m²
2. Calculate the safe load carrying capacity of the pile:
qs = qult / FOS
qs = 672.6 / 3
qs = 224.2 kN/m²
3. Calculate the area of the pile:
A = 0.5 × 0.5
A = 0.25 m²
4. Calculate the ultimate load carrying capacity of the pile:
Qult = qs × A
Qult = 224.2 × 0.25
Qult = 56.05 kN
5. Calculate the safe working load of the pile:
Qsafe = Qult / α
Qsafe = 56.05 / 0.6
Qsafe = 93.42 kN
6. Calculate the length of the pile required to carry the safe working load:
L = Qsafe / σ
where,
σ = Allowable stress in the pile = Qult / L
Assume a length for the pile and calculate σ
If σ > qs, increase the length and repeat the calculation
If σ < qs,="" decrease="" the="" length="" and="" repeat="" the="" />
Let's assume the length of the pile as 20 m
σ = Qult / L
σ = 56.05 / 20
σ = 2.8025 kN/m²
L = Qsafe / σ
L = 93.42 / 2.8025
L = 33.33 m
Assuming a pile length of 20 m gives a σ value less than qs, so we need to increase the length of the pile.
Let's assume the length of the pile as 25 m
σ = Qult / L
σ = 56.05 / 25
σ = 2.242 kN/m²
L = Qsafe / σ
L = 93.42 / 2.242
L = 41.65 m
Assuming a pile length of 25 m gives a σ value greater than qs, so we need to decrease the length of the
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Precast concrete pile of size 50 cm × 50 cm is to be driven into clay strata. The unconfined compressive strength of which is 110 kN/m2. Then the length required to carry a safe working load of 500 kN with FOS = 3 and α = 0.6 is _______ m.a)18b)21c)23d)17Correct answer is option 'B'. Can you explain this answer?
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Precast concrete pile of size 50 cm × 50 cm is to be driven into clay strata. The unconfined compressive strength of which is 110 kN/m2. Then the length required to carry a safe working load of 500 kN with FOS = 3 and α = 0.6 is _______ m.a)18b)21c)23d)17Correct answer is option 'B'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about Precast concrete pile of size 50 cm × 50 cm is to be driven into clay strata. The unconfined compressive strength of which is 110 kN/m2. Then the length required to carry a safe working load of 500 kN with FOS = 3 and α = 0.6 is _______ m.a)18b)21c)23d)17Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Precast concrete pile of size 50 cm × 50 cm is to be driven into clay strata. The unconfined compressive strength of which is 110 kN/m2. Then the length required to carry a safe working load of 500 kN with FOS = 3 and α = 0.6 is _______ m.a)18b)21c)23d)17Correct answer is option 'B'. Can you explain this answer?.
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