Page 349 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

SITE UTILITY SYSTEMS

SITE UTILITY SYSTEMS 6.71

K = bedding constant
L = total load transmitted to pipe, lb/in
T
R = mean radius of pipe, in
E = modules of elasticity
I = moment of inertia
S = modulus soil reaction, psi

Discussion:
1. LF is the lag factor, which allows for continued deflection of pipe after the total load has
been developed. It is an empirical number, with a recommended value of 1.25 for good
backfill (85 percent density), or 1.50 for excellent backfill (95 percent density).
2. K is a factor depending on the width of bedding. An average value of 0.1 is recommended.
3. L is the total load (earth, superimposed, railroad) in lb/in of pipe length.
T
4. R is the radius of pipe measured from the center of the corrugation. For this formula,
one-half of the nominal size should be used.
5. To determine I, refer to Table 6.24 for the correct value of corrugated pipe, based on the
gauge of steel selected. For plastic pipe, individual manufacturers should be consulted
because of the great diversity of materials available.
6
6. E is 10 for all pipe sizes.
7. S is soil reaction modulus in psi. S is dependent on the degree of compaction of backfill
around the pipe. This number has not been fully correlated for backfilled soil. Estimates
by the Bureau of Public Roads are 700 for good backfill at 85 percent compaction and
1400 for excellent backfill at 95 percent compaction. The value established for good or
excellent backfill should be used in Eq. (6.18).
In certain cases, other structural failures for corrugated steel pipe may have to be considered
during design. Seam, buckling, handling, and installation strengths and conduit wall compres-
sion strength may have to be determined. Refer to the Handbook of Steel Drainage and Highway
Construction Products, published by the American Iron and Steel Institute, for a description of
the method of calculating all the above design parameters, if they are required.

SEWER CLEANING AND REPAIR

CLEANING METHODS

There are many options available to clean sewer piping, manholes, and drainage inlets. The
following paragraphs will describe the methods and applications associated with each.

TABLE 6.24 Moment of Inertia for Corrugated Steel Pipe

Corrugation pitch & depth 16 gauge 14 gauge 12 gauge
2 × 1/2 0.00194 0.00246 0.00354
2 2/3 × 1/2 0.00189 0.00239 0.00343

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