Graded Granular Material
Graded granular material of 14 to 5 mm or 20 to 5 mm may be used for all pipe sizes and in addition 40 to 5 mm may be used for pipes of larger than 500 mm diameter.
Class D – Trimmed trench bottom.
Bedding Factor 1.1
Class N – Granular or “as-dug” material.
Bedding Factor 1.1
Class F – Granular material.
Bedding Factor 1.9
Class B – Granular material.
Bedding Factor 2.5
Class S – Granular material
Bedding Factor 2.5
Unreinforced concrete bed
Bedding Factor 2.6
Unreinforced concrete surround
Bedding Factor 2.6
Reinforced concrete bed
Bedding factor 3.4 (0.4 % Steel)
Reinforced concrete surround
Bedding factor 4.8 (2X 1.0 % steel)
Key Information about the figures above.
Vitrified clay pipe
Graded or all-in aggregate or compacted sand or suitable as-dug material
Fill selected from excavated material and lightly compacted by hand
Concrete with 28 day cube strength
Single size or graded granular material
Undisturbed natural soil
Precautions are necessary for pipes laid in water bearing soils to prevent the fine sand and silt being carried by water into the granular material.
The thickness of bottom bedding (a) = min. Of 100mm or 1/6 Bc whichever is greater under the pipe barrel and 50mm minimum under the socket but in rock min. 200mm or 1/4Bc which is greater under pipes barrel and 150mm minimum under the socket.
The minimum depths of cover are 1.2m under roads and 0.6m in fields and gardens. Where pipes must be laid at depths less than this, precautions must be must be taken to reduce the risk of damage.
Nominal bore of pipe (mm) Size of material (mm)
Single sized Graded
15-20 10 or 14 14 to 5
250 to 300 10, 14 or 20 14 to 5 or 20 to 5
350 to 500 14 or 30 14 to 5 or 20 to 5
600 14, 20 or 40 14 to 5 or 20 to 5 or 40 to 5
2nd Industrial City, New Saniya,
New Al – Kharj Highway,
P.O. Box 17952,
Ar – Riyadh 11494,
Kingdom Of Saudi Arabia.
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