Proper Bedding for Pvc Pressure (1)

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Ast k
h e E n g i n e e r
PROPER BEDDING FOR PVC PRESSURE PIPE
By Mike Luckenbill Southwestern Regional Engineer
Historically, a flexible pipe has been zontal
diameter expands, it engages the defined as a
conduit that will deflect at least passive
resistance of the soil support at the two
percent without any sign of structural sides of
the pipe. At the same time, the distress, such
as injurious cracking. compression of the
vertical diameter However, for a conduit to
truly behave as a relieves the pipe of the major
portion of the flexible pipe when buried, it is
required that vertical soil load, which is then
carried by the pipe be more yielding than the
embed- the surrounding soil through the mecha-
ment soil surrounding it. This is the source nism
of an arching action over the pipe. HISTORICALLY,
A FLEXIBLE PIPE HAS BEEN DEFINED AS A CONDUIT
THAT WILL DEFLECT AT LEAST TWO PERCENT WITHOUT
ANY SIGN OF STRUCTURAL DISTRESS, SUCH AS
INJURIOUS CRACKING.
Vsystem. Two of the main considera-
arious parameters must be consid-
ered when designing a buried piping
tions should be the pipe properties and the soil
envelope around the pipe. To the layman, the word
soil can mean different things. To engineers
involved in pipe burial, soil is any earthen
material excluding bedrock. Soil has been used
as a construction mate- rial throughout history.
Soil is important not only as a material upon
which the structure rests, but also for support
and load transfer. The soil envelope transfers
surface and gravity loads to, from, and around
the struc- ture.
Superimposed loads on buried PVC pipe fall into
two categories - earth loads and live loads. In
the design of any buried pip- ing system, both
categories of superim- posed loads must be
considered. In accor- dance with common design
practice, earth CONTINUED ON PAGE 14
of flexible pipes external-load-carrying
capacity. Under soil load, the pipe tends to
deflect. The vertical diameter is com- pressed
and the horizontal diameter expands by
approximately the same amount in both
directions. When the hori-
SIDE PRISM
SIDE PRISM
SIDE PRISM
SIDE PRISM
CENTRAL PRISM
CENTRAL PRISM
Shearing Forces Over Rigid Pipe Shearing Forces
Increase The Load
Shearing Forces Over Flexible Pipe Shearing
Forces Decrease The Load
Figure A Comparing Trench Loads for Flexible and
Rigid Products
P V C P I P E N E W S S P R I N G 2 0 0 4
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2
EXCAVATED TRENCH WIDTH FINAL BACKFILL
PIPE WIDTH
COVER
INITIAL BACKFILL
PIPE EMBEDMENT
PIPE SPRINGLINE ZONE
PIPE
HAUNCHING BEDDING FOUNDATION (MAY NOT BE
REQUIRED)
Figure B Trench Embedment Terminology
on earth loading technology for buried
con- buried pipe is modified by the response of
duits throughout the world is related,
in the pipe and the relative movement of the
CONTINUED FROM PAGE 13
loads and live loads are treated as separate
design parameters. The first solution to the
problem of soil- induced loads on buried pipe
was pub- lished by Professor Anson Marston at
Iowa State University in 1913. Since then, the
Marston Theory of Loads on Underground Conduits
has been used in determining the loads on buried
pipe. Much of the research
ALMOST ANY REASONABLE SOIL STRUCTURE WILL WORK
FOR PVC PRESSURE PIPE BURIAL.
part, to Marston's load theory. The basic
concept of the theory is that the load due to
the weight of the column of soil above a
side columns of soil to the central column. When
the side columns of soil between the pipe and
the trench wall (pipe zone) are
Table 1 Average Values Of Modulus Of Soil Reaction, E' (For Initial Flexible Pipe Deflection) Table 1 Average Values Of Modulus Of Soil Reaction, E' (For Initial Flexible Pipe Deflection) Table 1 Average Values Of Modulus Of Soil Reaction, E' (For Initial Flexible Pipe Deflection) Table 1 Average Values Of Modulus Of Soil Reaction, E' (For Initial Flexible Pipe Deflection) Table 1 Average Values Of Modulus Of Soil Reaction, E' (For Initial Flexible Pipe Deflection) Table 1 Average Values Of Modulus Of Soil Reaction, E' (For Initial Flexible Pipe Deflection)
ASTM D2321 Embedment Material Classification ASTM D2321 Embedment Material Classification E' for Degree of Compaction of Haunching, in psi E' for Degree of Compaction of Haunching, in psi E' for Degree of Compaction of Haunching, in psi E' for Degree of Compaction of Haunching, in psi
ASTM D2321 Embedment Material Classification ASTM D2321 Embedment Material Classification Dumped Slight lt 85 Proctor Moderate 85 - 95 Proctor High gt 95 Proctor
Manufactured Granular Angular Class I 1,000 3,000 3,000 3,000
Clean Sand Gravel Class II 200 1,000 2,000 3,000
Sand Gravel with Fines Class III 100 400 1,000 2,000
Silt Clay Class IV 50 200 400 1,000
Organic Materials Class V No data available consult a competent soils engineer otherwise use E 0 No data available consult a competent soils engineer otherwise use E 0 No data available consult a competent soils engineer otherwise use E 0 No data available consult a competent soils engineer otherwise use E 0
A more detailed table is available for download from Uni-Bells website, www.uni-bell.org. The table is in Uni-Bells technical report Deflection The Pipe/Soil Mechanism, UNI-TR-1. A more detailed table is available for download from Uni-Bells website, www.uni-bell.org. The table is in Uni-Bells technical report Deflection The Pipe/Soil Mechanism, UNI-TR-1. A more detailed table is available for download from Uni-Bells website, www.uni-bell.org. The table is in Uni-Bells technical report Deflection The Pipe/Soil Mechanism, UNI-TR-1. A more detailed table is available for download from Uni-Bells website, www.uni-bell.org. The table is in Uni-Bells technical report Deflection The Pipe/Soil Mechanism, UNI-TR-1. A more detailed table is available for download from Uni-Bells website, www.uni-bell.org. The table is in Uni-Bells technical report Deflection The Pipe/Soil Mechanism, UNI-TR-1. A more detailed table is available for download from Uni-Bells website, www.uni-bell.org. The table is in Uni-Bells technical report Deflection The Pipe/Soil Mechanism, UNI-TR-1.
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P V C P I P E N E W S S P R I N G 2 0 0 4
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more compressible than the pipe, this causes the
pipe to assume load generated across the width of
the trench. This is typically the case for rigid
prod- ucts like concrete and clay. However, when
pipe has the ability to deflect without
cracking, this produces a situation that allows
the central prism of soil (directly over the
pipe) to settle more in relation to the adjacent
soil columns (between the pipe and the trench
wall). This settlement produces shearing forces
which reduce the load on a flexible pipe to an
amount less than the weight of the prism directly
over it. The two scenarios are shown in Figure A
on page 13. Regardless of pipe stiffness, as
soil in the trench settles or moves downward
compared to the trench sidewall, friction forces
are generated which act to reduce the weight of
the trench-wide soil col- umn. Marston's Load
Theory predicts and accounts for these
frictional shearing forces. Figure B on page 14
shows a typical trench cross- section denoting
standard nomenclature used in the plastic pipe
industry. The word bedding is gener- ally
accepted as the soil structure around the pipe
and not necessarily the bedding upon which the
pipe rests. This would include the haunching and
initial backfill areas. The soil structure
requirements for pressure pipe are less
stringent than for gravity sewer pipe. This is
primarily due to the fact that pressure pipe is
usually buried at shallow depths. Also, pressure
pipes tend to have thicker walls than CONTINUED
ON PAGE 16
BEDDING ANGLE
BEDDING
VALUES OF BEDDING CONSTANT ,K
BEDDING ANGLE K
0 0.110
30 0.108
45 0.105
60 0.102
90 0.096
120 0.090
180 0.083
Figure C Bedding Angle Defined
Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads
Height of Cover Live Load Prism 2 H20 E80 Prism 4 H20 E80 Prism 6 H20 E80 Prism 8 H20 E80 Prism 10 H20 E80
E Value DR 14
50 0.13 0.58 2.25 0.27 0.49 1.75 0.40 0.51 1.66 0.54 0.59 1.43 0.67 0.67 1.28
200 0.12 0.54 2.10 0.25 0.46 1.63 0.37 0.48 1.54 0.50 0.55 1.33 0.62 0.62 1.20
400 0.11 0.50 1.92 0.23 0.42 1.49 0.34 0.44 1.42 0.46 0.50 1.22 0.57 0.57 1.10
1000 0.09 0.40 1.54 0.18 0.34 1.19 0.27 0.35 1.13 0.37 0.40 0.97 0.46 0.46 0.88
2000 0.07 0.30 1.15 0.14 0.25 0.89 0.21 0.26 0.85 0.27 0.30 0.73 0.34 0.34 0.66
E Value DR 18
50 0.29 1.26 4.89 0.58 1.07 3.79 0.87 1.11 3.60 1.16 1.28 3.10 1.45 1.45 2.79
200 0.25 1.09 4.22 0.50 0.92 3.27 0.75 0.96 3.10 1.00 1.11 2.67 1.25 1.25 2.40
400 0.21 0.92 3.57 0.42 0.78 2.76 0.64 0.81 2.62 0.85 0.94 2.26 1.06 1.06 2.03
1000 0.14 0.63 2.43 0.29 0.53 1.89 0.43 0.55 1.79 0.58 0.64 1.54 0.72 0.72 1.39
2000 0.09 0.41 1.59 0.19 0.35 1.23 0.28 0.36 1.17 0.38 0.42 1.01 0.47 0.47 0.91
E Value DR 21
50 0.46 1.99 7.71 0.92 1.68 5.97 1.37 1.76 5.67 1.83 2.02 4.89 2.29 2.29 4.39
200 0.37 1.59 6.16 0.73 1.34 4.77 1.10 1.40 4.53 1.46 1.62 3.90 1.83 1.83 3.51
400 0.29 1.25 4.86 0.58 1.06 3.76 0.87 1.11 3.57 1.15 1.27 3.08 1.44 1.44 2.77
1000 0.18 0.77 2.97 0.35 0.65 2.30 0.53 0.68 2.19 0.71 0.78 1.88 0.88 0.88 1.69
2000 0.11 0.47 1.81 0.21 0.39 1.40 0.32 0.41 1.33 0.43 0.47 1.14 0.54 0.54 1.03
E Value DR 25
50 0.75 3.23 12.56 1.49 2.74 9.73 2.24 2.86 9.23 2.98 3.29 7.96 3.73 3.73 7.15
200 0.53 2.29 8.91 1.06 1.94 6.90 1.59 2.03 6.55 2.12 2.34 5.65 2.65 2.65 5.07
400 0.38 1.65 6.42 0.76 1.40 4.97 1.14 1.46 4.72 1.53 1.68 4.07 1.91 1.91 3.66
1000 0.21 0.90 3.49 0.42 0.76 2.71 0.62 0.80 2.57 0.83 0.92 2.21 1.04 1.04 1.99
2000 0.12 0.51 1.99 0.24 0.43 1.54 0.35 0.45 1.46 0.47 0.52 1.26 0.59 0.59 1.13
E Value DR 26
50 0.83 3.59 13.95 1.66 3.04 10.80 2.49 3.18 10.26 3.31 3.66 8.84 4.14 4.14 7.94
200 0.57 2.47 9.59 1.14 2.09 7.43 1.71 2.18 7.05 2.28 2.51 6.07 2.85 2.85 5.46
400 0.40 1.74 6.77 0.80 1.47 5.24 1.21 1.54 4.98 1.61 1.77 4.29 2.01 2.01 3.85
1000 0.21 0.93 3.59 0.43 0.78 2.78 0.64 0.82 2.64 0.85 0.94 2.28 1.07 1.07 2.05
2000 0.12 0.52 2.02 0.24 0.44 1.56 0.36 0.46 1.48 0.48 0.53 1.28 0.60 0.60 1.15
P V C P I P E N E W S S P R I N G 2 0 0 4
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CONTINUED FROM PAGE 15
a comparable gravity pipe in order to han- dle
the pressure capacity typically speci- fied.
This often results in external load capabilities
that far exceed the design requirement. As a
consequence, almost any reasonable soil
structure will work for PVC pressure pipe
burial. The bedding factor is also used in
burial equations. Precise values are shown in
Figure C on page 15. The bedding factor has
little effect on results of burial calcula-
tions and is usually taken as 0.100. What is the
modulus of soil reaction? It is
symbolically represented as E. The aver- becomes
increasingly important as depth age values are
shown in Table 1 on page 14. of cover increases.
However, at relatively This variable is very
important in flexible shallow depths in the 3 to
10 foot range E
THE STRENGTH AND SUITABILITY OF THE PVC PIPE FOR
BURIAL MADE IT EQUAL TO (OR BETTER THAN) OTHER
TRADITIONAL PIPING MATERIALS...
pipe burial calculations. E in the haunch area
is a measure of the ability of the soil to
absorb live and dead loads transmitted through
the pipe as it deflects over time. E
values of 700 to 2,000 psi will cover almost any
burial situation as long as there is full
support in the haunches of the pipe.
CONTINUED ON PAGE 18
Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads
Height of Cover Live Load Prism 2 H20 E80 Prism 4 H20 E80 Prism 6 H20 E80 Prism 8 H20 E80 Prism 10 H20 E80
E Value DR 32.5
50 1.44 6.24 24.22 2.88 5.28 18.77 4.32 5.52 17.81 5.76 6.35 15.35 7.20 7.20 13.79
200 0.80 3.49 13.53 1.61 2.95 10.48 2.41 3.08 9.95 3.22 3.55 8.57 4.02 4.02 7.70
400 0.51 2.19 8.52 1.01 1.86 6.60 1.52 1.94 6.26 2.02 2.23 5.40 2.53 2.53 4.85
1000 0.24 1.04 4.04 0.48 0.88 3.13 0.72 0.92 2.97 0.96 1.06 2.56 1.20 1.20 2.30
2000 0.13 0.55 2.15 0.26 0.47 1.66 0.38 0.49 1.58 0.51 0.56 1.36 0.64 0.64 1.22
E Value DR 41
50 2.31 10.01 38.88 4.62 8.47 30.12 6.93 8.85 28.59 9.24 10.19 24.63 11.55 11.55 22.13
200 1.02 4.42 17.14 2.04 3.74 13.28 3.05 3.90 12.60 4.07 4.49 10.86 5.09 5.09 9.76
400 0.58 2.53 9.82 1.17 2.14 7.61 1.75 2.24 7.22 2.33 2.58 6.22 2.92 2.92 5.59
1000 0.26 1.11 4.31 0.51 0.94 3.34 0.77 0.98 3.17 1.02 1.13 2.73 1.28 1.28 2.45
2000 0.13 0.57 2.22 0.28 0.48 1.72 0.40 0.51 1.64 0.53 0.58 1.41 0.66 0.66 1.27
E Value DR 51
50 3.22 13.94 54.13 6.43 11.79 41.93 9.65 12.33 39.80 12.86 14.19 34.30 16.08 16.08 30.82
200 1.16 5.04 19.57 2.33 4.27 15.16 3.49 4.46 14.39 4.65 5.13 12.40 5.81 5.81 11.14
400 0.63 2.72 10.57 1.26 2.30 8.19 1.88 2.41 7.78 2.51 2.77 6.70 3.14 3.14 6.02
1000 0.26 1.14 4.44 0.53 0.97 3.44 0.79 1.01 3.27 1.06 1.17 2.82 1.32 1.32 2.53
2000 0.13 0.58 2.26 0.27 0.49 1.75 0.40 0.51 1.66 0.54 0.59 1.43 0.67 0.67 1.29

Height of Cover Live Load Prism 12 H20 E80 Prism 14 H20 E80 Prism 16 H20 E80 Prism 18 H20 E80 Prism 20 H20 E80
E Value DR 14
50 0.80 0.80 1.25 0.94 0.94 1.27 1.07 1.07 1.35 1.21 1.21 1.43 1.34 1.34 1.51
200 0.75 0.75 1.16 0.87 0.87 1.19 1.00 1.00 1.26 1.12 1.12 1.33 1.25 1.25 1.40
400 0.69 0.69 1.07 0.80 0.80 1.09 0.91 0.91 1.15 1.03 1.03 1.22 1.14 1.14 1.29
1000 0.55 0.55 0.85 0.64 0.64 0.87 0.73 0.73 0.92 0.82 0.82 0.97 0.91 0.91 1.03
2000 0.41 0.41 0.64 0.48 0.48 0.65 0.55 0.55 0.69 0.62 0.62 0.73 0.68 0.68 0.77
E Value DR 18
50 1.74 1.74 2.71 2.04 2.04 2.76 2.33 2.33 2.93 2.62 2.62 3.10 2.91 2.91 3.27
200 1.50 1.50 2.34 1.75 1.75 2.38 2.01 2.01 2.53 2.26 2.26 2.67 2.51 2.51 2.82
400 1.27 1.27 1.98 1.48 1.48 2.01 1.69 1.69 2.14 1.91 1.91 2.26 2.12 2.12 2.38
1000 0.87 0.87 1.35 1.01 1.01 1.37 1.16 1.16 1.46 1.30 1.30 1.54 1.45 1.45 1.63
2000 0.57 0.57 0.88 0.66 0.66 0.90 0.76 0.76 0.95 0.85 0.85 1.01 0.95 0.95 1.06
E Value DR 21
50 2.75 2.75 4.28 3.21 3.21 4.35 3.66 3.66 4.62 4.12 4.12 4.89 4.58 4.58 5.15
200 2.20 2.20 3.42 2.56 2.56 3.48 2.93 2.93 3.69 3.29 3.29 3.90 3.66 3.66 4.12
400 1.73 1.73 2.70 2.02 2.02 2.74 2.31 2.31 2.91 2.60 2.60 3.08 2.89 2.89 3.25
1000 1.06 1.06 1.65 1.24 1.24 1.68 1.41 1.41 1.78 1.59 1.59 1.88 1.77 1.77 1.99
2000 0.64 0.64 1.00 0.75 0.75 1.02 0.86 0.86 1.08 0.97 0.97 1.14 1.07 1.07 1.21
E Value DR 25
50 4.48 4.48 6.97 5.22 5.22 7.09 5.97 5.97 7.52 6.71 6.71 7.96 7.46 7.46 8.39
200 3.18 3.18 4.94 3.70 3.70 5.03 4.23 4.23 5.34 4.76 4.76 5.65 5.29 5.29 5.95
400 2.29 2.29 3.56 2.67 2.67 3.62 3.05 3.05 3.85 3.43 3.43 4.07 3.81 3.81 4.29
1000 1.25 1.25 1.94 1.45 1.45 1.97 1.66 1.66 2.09 1.87 1.87 2.21 2.08 2.08 2.33
2000 0.71 0.71 1.10 0.83 0.83 1.12 0.94 0.94 1.19 1.06 1.06 1.26 1.18 1.18 1.33

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P V C P I P E N E W S S P R I N G 2 0 0 4
5
Type 1 Flat-bottom trench. Loose embedment. E
50 psi (340 kPa), K 0.110
Type 2 Flat-bottom trench. Embedment lightly
consolidated to centerline of pipe. E 200 psi
(1,380 kPa), K 0.110
Type 3 Type 4
Pipe bedded on 4 in. (100 mm) minimum of Pipe
bedded on sand, gravel, or crushed stone loose
soil. Embedment lightly consolidated to depth
of 1/8 pipe diameter, 4 in. (100mm)
to top of pipe. E 400 psi (2,760 kPa), K
0.102
minimum. Embedment compacted to top of pipe.
(Approximately 80 percent Standard Proctor,
AASHTO T-99 or ASTM D 698.) E 1,000 psi (6,900
kPa), K 0.096
Figure D Notation
Type 5 Pipe embedded in compacted granular
material to centerline of pipe. Compacted
granular or select material to top of pipe.
(Approximately 90 percent Standard Proctor,
AASHTO T-99 or ASTM D 698) E 2,000 psi
(13,800 kPa), K 0.083
NOTE Required embedment type will depend on the
pipes dimension ratio, internal operating
pressure, and external load, and shall be
specified by the purchaser. (see Sec. 5.3)
Flat-bottom is defined as undisturbed earth.
Loose soil or select material is defined as
native soil excavated from the trench, free of
rocks, foreign materials, and frozen earth. A
soft loose soil bedding will contour to the
pipe bottom. Caution must be excercised to ensure
proper placement of embedment material under the
haunches of the pipe.
Figure D Typical Trench Types in the PVC
Installation Standard, AWWA C605
Type 2 Flat-bottom trench. Backfill lightly
consolidated to centerline of pipe.
Type 1 Flat-bottom trench. Loose backfill.
Type 3 Type 4 Pipe bedded on 4 in. (100 mm)
minimum of Pipe bedded on sand, gravel, or
crushed stone loose soil. Backfill lightly
consolidated to depth of 1/8 pipe diameter, 4
in. (100mm) to top of pipe. minimum. Backfill
compacted to top of pipe. (Approximately 80
percent Standard Proctor, AASHTO T-99.)
Figure E Notation
Type 5 Pipe embedded in compacted granular
material to centerline of pipe. Compacted
granular or select material to top of pipe.
(Approximately 90 percent Standard Proctor,
AASHTO T-99.)
For 14-in. (355-mm) and larger pipe,
consideration should be given to the use of
laying conditions other than type 1.
Flat-bottom is defined as undisturbed earth.
Loose soil or select material is defined as
native soil excavated from the trench, free of
rocks, foreign materials, and frozen earth. A
soft loose soil bedding will contour to the
pipe bottom. Caution must be excercised to ensure
proper placement of embedment material under the
haunches of the pipe.
Figure E Typical Trench Types in the Ductile
Iron Installation Standard, AWWA C600
P V C P I P E N E W S S P R I N G 2 0 0 4
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Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads Table 2 (cont.) Calculated Deflections Of Buried PVC Pressure Pipe Deflection (percent) For Prism, Highway H20, or Railway E80 Loads
Height of Cover Live Load Prism 12 H20 E80 Prism 14 H20 E80 Prism 16 H20 E80 Prism 18 H20 E80 Prism 20 H20 E80
E Value DR 26
50 4.97 4.97 7.73 5.80 5.80 7.87 6.63 6.63 8.35 7.46 7.46 8.84 8.29 8.29 9.32
200 3.42 3.42 5.32 3.99 3.99 5.41 4.56 4.56 5.74 5.13 5.13 6.08 5.69 5.69 6.41
400 2.41 2.41 3.75 2.81 2.81 3.82 3.22 3.22 4.05 3.62 3.62 4.29 4.02 4.02 4.52
1000 1.28 1.28 1.99 1.49 1.49 2.03 1.71 1.71 2.15 1.92 1.92 2.28 2.13 2.13 2.40
2000 0.72 0.72 1.12 0.84 0.84 1.14 0.96 0.96 1.21 1.08 1.08 1.28 1.20 1.20 1.35
E Value DR 32.5
50 8.63 8.63 13.43 10.07 10.07 13.67 11.51 11.51 14.51 12.95 12.95 15.35 14.39 14.39 16.19
200 4.82 4.82 7.51 5.63 5.63 7.64 6.43 6.43 8.11 7.24 7.24 8.58 8.04 8.04 9.04
400 3.04 3.04 4.72 3.54 3.54 4.81 4.05 4.05 5.10 4.55 4.55 5.40 5.06 5.06 5.69
1000 1.44 1.44 2.24 1.68 1.68 2.28 1.92 1.92 2.42 2.16 2.16 2.56 2.40 2.40 2.70
2000 0.77 0.77 1.19 0.89 0.89 1.21 1.02 1.02 1.29 1.15 1.15 1.36 1.28 1.28 1.44
E Value DR 41
50 13.86 13.86 21.56 16.17 16.17 21.94 18.48 18.48 23.28 20.79 20.79 24.64 23.09 23.09 25.98
200 6.11 6.11 9.51 7.13 7.13 9.68 8.15 8.15 10.27 9.16 9.16 10.86 10.18 10.18 11.45
400 3.50 3.50 5.45 4.08 4.08 5.54 4.67 4.67 5.88 5.25 5.25 6.22 5.83 5.83 6.56
1000 1.53 1.53 2.39 1.79 1.79 2.43 2.05 2.05 2.58 2.30 2.30 2.73 2.56 2.56 2.88
2000 0.79 0.79 1.23 0.92 0.92 1.26 1.06 1.06 1.33 1.19 1.19 1.41 1.32 1.32 1.49
E Value DR 51
50 19.29 19.29 30.02 22.51 22.51 30.55 25.72 25.72 32.42 28.94 28.94 34.30 32.15 32.15 36.17
200 6.98 6.98 10.86 8.14 8.14 11.05 9.30 9.30 11.72 10.47 10.47 12.40 11.63 11.63 13.08
400 3.77 3.77 5.86 4.40 4.40 5.97 5.03 5.03 6.33 5.65 5.65 6.70 6.28 6.28 7.07
1000 1.58 1.58 2.46 1.85 1.85 2.51 2.11 2.11 2.66 2.38 2.38 2.82 2.64 2.64 2.97
2000 0.81 0.81 1.25 0.94 0.94 1.28 1.07 1.07 1.35 1.21 1.21 1.43 1.34 1.34 1.51
the maximum particle size it recommends in
contact with the pipe. ASTM D2774-01, paragraph
9.6, recommends embedment material no greater
than 1/2 inch for 4-inch diameter pipe, 3/4 inch
for 6- and 8-inch diameter pipes, 1-inch for
pipe diameters from 10- to 16-inches, and 1-1/2
inch for pipes over 16-inches in
diameter. Figure E on page 17 is from AWWA
C600-99 and it points out the similarity between
the installation of PVC pressure pipe and
Ductile Iron pressure pipe. When AWWA C605 was
written, the committee provided
sure pipe installation instructions see Uni-
Bell PVC Pipe Associations UNI-PUB-9, ANSI/AWWA
C605, or AWWA M23. TO SUMMARIZE Almost any
trench type is sufficient assuming contact in
the haunch area. To reemphasize It is
important for installers to realize that
extremely high compaction densities are not
necessary in shallow burial conditions. There is
one exception. Shallow burial with live loads
may require adequate compaction around the pipe
and up to the paved sur- face. References Moser
, A.P., Buried Pipe Design, McGraw-Hill, Inc.,
New York, New York, 1990, pp. 1-3.
CONTINUED FROM PAGE 16
Deflection data in Table 2 substantiate this. It
is important for installers to realize that
extremely high compaction densities are not
necessary in shallow burial conditions. There is
one exception. Shallow burial with live loads
may require adequate com- paction around the
pipe and up to the paved surface. (See Pipe
Burial How Deep or Shallow Can PVC Pipe Be
Buried in the summer 2001 edition of the News
for additional discussion.)
IT IS IMPORTANT FOR INSTALLERS TO REALIZE THAT
EXTREMELY HIGH COMPACTION DENSITIES ARE NOT
NECESSARY IN SHALLOW BURIAL CONDITIONS.
ANSI/AWWA C605-94, AWWA Standard for
Underground Installation of Polyvinyl Chloride
(PVC) Pressure Pipe and Fittings for Water,
American Water Works Association, Denver,
Colorado, p. 7.
The PVC installation standard AWWA C605 details
common embedment types, which are shown in
Figure D on page 17. Figure D also suggests
values for E and K, which may be used for
calculating the pipe deflection as recommended
in AWWA Manual M23. The maximum embedment
particle size rec- ommended in C605 is 3/4 inch
crushed rock or 1-1/2 inch rounded rock.
However, we make note of a recommendation from
ASTM D2774. This installation standard
recognizes the fact that the pipe diameter
should also be considered when selecting
trench types that were identical to the ones in
the ductile iron installation standard. The
strength and suitability of the PVC pipe for
burial made it equal to (or better than) other
traditional piping materials such as ductile
iron. Please note that the cross-sec- tion
diagrams are nearly identical in both standards
(other than the type of cross- hatching
employed). The only significant difference is in
the Type 1 embedment, which is not recommended
for Ductile Iron Pipe 14-inch and larger. For
detailed pres-
ANSI/AWWA C600-99, AWWA Standard for
Installation of Ductile-Iron Water Mains and
Their Appurtances, American Water Works
Association, Denver, Colorado, p. 8.
ASTM D 2774-01, Standard Practice for
Underground Installation of Thermoplastic
Pressure Piping, Volume 8.04, ASTM
International, West Conshohocken, Pennsylvania.
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