Specified Trench Width*
| |||
---|---|---|---|
Pipe Size Inside Diameter
|
Concrete Pipe
|
Metal Pipe
| |
48 inches and less
|
Outside diameter of pipe measured at the bell, plus 1.0 foot
on each side of the pipe.
|
Outside diameter of pipe, measured at the end of the pipe section
without band, plus 1.0 foot on each side of the pipe
| |
Over 48 inches
|
Outside diameter of pipe, measured at the bell, plus 1.25 feet
on each side of the pipe.
|
Outside diameter of pipe, measured at the end of the pipe section
without band, plus 1.25 feet on each side of the pipe
|
NOTES:
| ||
---|---|---|
* Specified trench widths may be increased by a tolerance one
foot on each side of the trench.
|
When rock, hard, shale, or any unyielding material is encountered in the trench, it shall be excavated for the full width of the trench below the proposed elevation of the bottom of the pipe for a depth of 1/4 inch per foot of fill over the pipe to a minimum depth of 12 inches and a maximum of 24 inches. The trench below the elevation of the bottom of the pipe shall be backfilled with selected fine compressible material and lightly compacted in four-inch layers, or when directed, with coarse aggregate meeting the requirements of § 18-402, Subsection 4B(3). The bed shall be shaped as specified in § 18-402, Subsection 2A, B, or C, for rigid pipe and § 18-402, Subsection 2C, for flexible pipe.
| |
When the material encountered is unstable, it shall be entirely removed under the pipe for the full width of the trench or as otherwise required for the particular condition, replaced with suitable material compacted to a satisfactory density, and the bed shaped as specified in § 18-402, Subsection 2A, B, or C.
|
Ultimate Strength of Pipe
|
Case 1, Maximum Embankment in Feet
|
Case 2, Maximum Embankment in Feet Imperfect Trench
| |||||
---|---|---|---|---|---|---|---|
Class of Bedding
|
Class of Bedding
| ||||||
Pipe Class D Load*
|
A
|
B
|
C
|
A
|
B
|
C
| |
Class I**
|
1,200D
| ||||||
Class II**
|
1,500D
| ||||||
Class III
|
2,000D
|
25
|
15
|
13
|
121
|
44
|
33
|
Class IV
|
3,000D
|
40
|
23
|
18
|
142
|
69
|
53
|
Class V
|
3,750D
|
47
|
29
|
24
|
180
|
87
|
67
|
4,000D***
|
NOTES:
| |
---|---|
* Ultimate strength of pipe per linear foot when tested by three
edge bearing method, where D is the nominal inside diameter of pipe
in feet.
| |
** Class I and II shall be used only for special designs.
| |
*** 4,000 D Cast-Iron Pipe shall be used when cover is shallow
and high impact and concentrated loading are involved.
|
Approved granulated blast-furnace slag will be acceptable. Approved
granulated blast-furnace slag is the glassy granular material formed
when molten blast-furnace slag is rapidly quenched by immersion in
water. Further, it is normally light gray or tan in color and it shall
not weigh more than 90 pounds per cubic foot nor less than 55 pounds
per cubic foot (dry rodded unit weight, PTM No. 609). The material
shall be reasonably uniform and free from harmful amounts of clay,
silt, vegetation or other substances determined to be deleterious.
It shall have a maximum size of two inches and not more than 20% passing
the No. 100 sieve.
| |
A change in the source of material may be made only with the
written permission of the Engineer. References given are to PennDOT
Form 408, Published in 1973.
|