EI 11C201
CEMP-E
1 March 1997
1920 kilograms (120 pounds) for mixed sand and gravel, 1760 kilograms (110 pounds) for
saturated top soil (loam and silt), 1920 kilograms (120 pounds) for ordinary damp clay, and 2080
kilograms (130 pounds) for saturated clay. The load coefficient C t is a function of the fill height H
divided by the width of trench Bt. An examination of the Marston formula will show the
importance of the trench being as narrow as practicable at and below the top of the pipe.
b. Uniformly distributed loads. Newmark's modification to the classical Boussinesq equation
results in the following formula to be used for calculating distributed loads on rigid and flexible
conduits.
Wd
= CspFBc
where:
Wd = vertical load on the conduit in kilograms per lineal meter (pounds per lineal foot)
Cs = surface load coefficient for buried conduits
p
= intensity of distributed load in kilograms per square meter (pounds per square
foot)
F
= impact factor, and
Bc = horizontal width or outside diameter of pipe in meters (feet).
The load coefficient Cs is dependent upon the area over which the load p acts. It will be selected
from table 5-1 as a function of the area width D and length M, each divided by twice the height of
fill H. The impact factor F will be determined with the use of the table 5-2.
Table 5-1. Surface load coefficient
Values of load coefficients, Cs, for concentrated and distributed
Superimposed loads vertically centered over conduit
D/2H
or
M/2H or L/2H
Bc/2H
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.2
1.5
2.0
5.0
0.1
0.019
0.037
0.053
0.067
0.079
0.0890
0.097
0.103
0.108
0.112
0.117
0.121
0.124
0.128
0.2
0.037
0.072
0.103
0.131
0.155
.174
0.189
0.2020
0.211
0.219
0.229
0.238
0.244
0.248
0.3
0.053
0.103
0.149
0.190
0.224
0.252
0.274
.292
0.306
0.318
0.333
0.345
0.355
0.360
0.4
0.067
0.131
0.190
0.241
0.284
0.320
0.349
0.373
0.391
0.405
0.425
0.440
0.454
0.460
0.5
0.079
0.155
0.224
0.284
0.336
0.379
0.414
0.441
0.463
0.481
0.505
0.525
0.540
0.548
0.6
0.089
0.174
0.252
0.320
0.379
0.428
0.467
0.499
0.524
0.544
0.572
0.596
0.613
0.624
0.7
0.097
0.189
0.274
0.349
0.414
0.467
0.511
0.546
0.584
0.597
0.628
0.650
0.674
0.688
0.8
0.103
0.202
0.292
0.373
0.441
0.499
0.546
0.584
0.615
0.639
0.674
0.703
0.725
0.740
0.9
0.108
0.211
0.306
0.391
0.463
0.524
0.574
0.615
0.647
0.673
0.711
0.742
0.766
0.784
1.0
0.112
0.219
0.318
0.405
0.481
0.544
0.597
0.639
0.673
0.701
0.740
0.774
0.800
0.816
1.2
0.117
0.229
0.333
0.425
0.505
0.572
0.628
0.674
0.711
0.740
0.783
0.820
0.849
0.868
1.5
0.121
0.238
0.345
0.440
0.525
0.596
0.650
0.703
0.742
0.774
0.820
0.861
0.894
0.916
2.0
0.124
0.244
0.355
0.454
0.540
0.613
0.674
0.725
0.766
0.800
0.849
0.894
0.930
0.956
5-2
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