Design requirements may vary greatly. Pipe design is approached differently for both materials and construction methods. The mechanics of the soil that will surround the pipes is a fundamental design aspect for the support characteristics, especially for flexible pipes. The soil type, density, and the moisture content are important characteristics.
Sewer pipe bedding is the material upon which the pipe is laid and serves as it foundation. Initial backfill is the material surrounding the pipe.
Classes of Bedding (LF = Load Factor, Bedding factor from pipe supplier):
Class A1 = LF = 2.2 = Native backfill lightly hand tamped full cover to crown of pipe with min 100 mm under pipe
Class A1 = LF = 2.8 = 67 crushed stone full pipe cover with 100 mm min. under pipe
Class A1 = LF = 3.4 = Reinforced concrete
Class B = LF = 1.9 = Native soil hand tamped or granular material to cover half the pipe with min 100 mm under the pipe with hand placed backfill above.
Class C = LF = 1.5 = shaped trench bottom with full pipe coverage with hand placed backfill
Class C = LF = 1.5= Min 100 mm native soil or granular bedding with shaped bottom, full pipe coverage with hand placed back fill
Class D = LF = 1.1 = flat or unshaped trench bottom with full pipe coverage with hand place backfill
Granular bedding material (Class B&C) may be used to facilitate a true grade on an imperfect or undercut trench bottom. Can also be used to arranged material to accommodate the pipe bells. Granular material is crushed rock aggregate with 1/4-3/4 inch particle size.
Calculate the Volume of Asphalt Removed
How many cubic yards of asphalt paving material will be required to pave over a trench 600 feet long, 4.5 feet wide using a 6 inch deep patch?
First convert the inches to feet and find the volume. Then convert ft3 to yd3.
Volume = 600 ft x 4.5 ft x 0.5 ft = 1,350 ft3
Volume = (1,350 ft3) / (27 ft3/yd3) = 50 yd3
1. Most commonly used for class B & C bedding applications
2. Fairly high BF 1.5-1.9
3. Moderately priced
4. Easy to work with
5. It is superior to sand or pea gravel due to water infiltration/washout.
6. Native soils a. Use in place of granular material because more available b. Low bedding factor of 1.1 must have undisturbed trench bottom c. Use high strength pipe
1. Follow manufacturer’s instructions
2. Use care when unloading at the site protect the bell and spigot
3. Use proper sized lifting equipment
4. For small diameter pipe <10 inches it may be hand laid on the bedding and connected 5. Larger pipe >10 inches should be supported in place so they can be connected while supported It may be necessary to use the weight of the pipe to obtain the proper grade.