What gradient is needed to produce a self-cleansing velocity in a 225 mm sewer line___________________?
Show answer Hide answer
Answer: C. 1 in 120
Explanation
For a larger two hundred twenty five millimeter sewer line, a gentler gradient of one in one hundred twenty is sufficient to achieve self-cleansing velocity. Increased pipe diameter provides a larger hydraulic radius, allowing gravity flow to maintain scouring velocities on flatter slopes. This moderate gradient prevents excessive drop over long pipeline runs while keeping suspended organic solids moving smoothly downstream. Hydraulic design principles demonstrate that larger conduits maintain higher flow depths and better efficiency at lower bed slopes. Engineers calculate minimum tractive force requirements to ensure that grit and organic matter do not settle on the pipe invert. Standard municipal design manuals tabulate recommended minimum slopes for every standard commercial sewer pipe diameter.
Option A of one in sixty is unnecessarily steep for a two hundred twenty five millimeter pipe, leading to excessive trench excavation depths. Option B of one in one hundred provides an adequate slope but exceeds the standard minimum requirement established for this pipe size. Option D is incorrect because the correct standard gradient of one in one hundred twenty is explicitly listed among the choices.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. Representing the upper circular diameter, what is the total depth of a New Egg-shaped sewer section_____________________?
Show answer Hide answer
Answer: D. 1.625 D
The New Egg-shaped sewer section is specifically proportioned with a total depth of one point six two five times the upper circular diameter D. This modified geometric design improves structural strength and enhances hyd...
Q2. When the flow depth inside a circular sewer equals 1/4th of its diameter D, what is the resulting wetted perimeter______________?
Show answer Hide answer
Answer: C. /3
When flow depth equals one-fourth of diameter, the wetted perimeter is proportional to D. Geometric arc length calculations for a circular pipe yield a perimeter of D divided by three. Trigonometric relations determine t...
Q3. What bed slope is necessary to achieve self-cleansing velocity in a 100 mm diameter sewer__________________?
Show answer Hide answer
Answer: A. 1 in 60
Smaller diameter sewers require steeper hydraulic gradients to maintain the minimum velocity needed to prevent silt deposition. A gradient of one in sixty generates sufficient gravitational flow velocity in a hundred mil...
Q4. If the discharge of a sewer running half is 628 1.p.s., i = 0.001, and n = 0.010, the diameter of the sewer, is__________________?
Show answer Hide answer
Answer: D. 1.69 m
Manning's open channel flow formula calculates circular sewer dimensions based on discharge, slope, and roughness. Solving the hydraulic equations for a sewer running half-full yields the required internal pipe diameter....
Q5. If a miner's safety lamp flame forms an explosive mixture in upper sewer layers, what does the sewer certainly contain_______________?
Show answer Hide answer
Answer: C. Methane
Methane is a flammable gas that collects near the top of poorly ventilated sewer pipes. Safety lamp flames react explosively when exposed to methane gas pockets in upper layers. This indicates dangerous anaerobic digesti...
Q6. If overland flow length to a drain is 8 km with a level drop of 12.4 m, what is the inlet time________________?
Show answer Hide answer
Answer: C. 4 hours
The Kirpich empirical formula relates overland flow length and elevation drop to calculate the time required for rainwater to reach a drain. An eight kilometer flow length combined with a twelve point four meter level dr...