Consecutive sight rails A and B feature reduced string levels of 203.575 m and 203.475 m respectively over a 10 m R.D. difference, yielding a sewer line gradient of_________________?
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Answer: C. 1 in 100 downward
Explanation
Gradient calculation divides the vertical elevation drop by the horizontal distance between reference points. Subtracting the reduced level of sight rail B from sight rail A gives a drop of zero point one meters. Dividing zero point one meters by the ten meter distance yields a downward slope of one in one hundred. Reduced level surveying establishes precise vertical elevations relative to a standardized datum plane. Sight rails and boning rods are traditional surveying tools used to control underground sewer pipe gradients. Downward gradients indicate that gravity flow proceeds from the higher sight rail toward the lower rail.
Construction surveyors set sight rails along trench alignments to guide pipe layers during excavation work. Maintaining accurate sewer gradients prevents wastewater stagnation and ensures proper gravity flow velocities. Civil engineering projects require precise leveling techniques to verify compliance with drainage design plans. Option A incorrectly specifies an upward slope direction despite the decreasing reduced levels. Option B calculates an erroneous gradient value that does not match the surveyed elevation difference. Option D suggests an incorrect upward slope and an inaccurate numerical distance ratio.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
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