For a protective embankment with mean height d, side slopes S:1 (horizontal:vertical), and length L, what is the area of one sloping face?
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Ad * d * S
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Bd^2 * (d * S)^2
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CL * d * sqrt(1 + S^2)
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D2 * L * d * sqrt(1 + S^2)
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EL * S / d
Answer
Correct Answer: L * d * sqrt(1 + S^2)
Explanation
Introduction / Context:When estimating protection works, pitching, or turfing on embankment slopes, we need the true sloping-face area, not just the vertical projection. Given the mean height, side slope, and length along the embankment, the surface area is found using basic geometry.
Given Data / Assumptions:
- Mean height of embankment face = d.
- Side slope ratio = S:1 (horizontal:vertical).
- Length along the embankment = L.
- We seek the area of a single sloping face.
Concept / Approach:The sloping length corresponding to vertical height d on a slope S:1 is the hypotenuse of a right triangle with vertical leg d and horizontal leg S*d. Hence, sloping length = d * sqrt(1 + S^2). The surface area of one face equals this sloping length multiplied by the embankment length L.
Step-by-Step Solution:Compute slope length: l_slope = d * sqrt(1 + S^2).Compute area of one face: A = L * l_slope = L * d * sqrt(1 + S^2).Select the option matching this expression.
Verification / Alternative check:Dimensional check: L (length) * d (length) gives area (length^2); the sqrt term is dimensionless.
Why Other Options Are Wrong:
- A and B are dimensionally or conceptually incorrect.
- D doubles the correct single-face area (might apply if both faces are considered).
- E is dimensionally inconsistent for area.
Common Pitfalls:Forgetting to use the true sloping length (using d alone); accidentally doubling for two faces when only one is asked.
Final Answer:L * d * sqrt(1 + S^2)