PVC drainage connection approval memo, Apr 1985

NYC 9/11 Public Portal Document

c Example: If an 18" Perma-Loc sewer pipe is installed in Class 111 material, having 75% compaction in the pipe zone with 7 feet of cover and 120 Ib/fP soil, and H20 (highway load) live load are imposed on the buried pipe, will the 6 in. - 12 in. recommended maximum long-term \ Initial deflection of 772% be exceeded ? \ backfill Pipe , Spring^ I Pipe Answer: 1. The combined (dead and ^embedment zone line live) load on the pipe will be approximately 1000 Ib/ft® or 1000 X 1.6 ft of Z; I pipe \| Haunching (pipe outside diameter (top of ribs] in... feet) = 1600 Ib/lin ft (per Figure 1). Enter Bedding table of prism loads under column 18 — (Zjmax. 6. in. Pipe diameter (inches) — and read . down until nearest figure to 1600 is Foundation reached, across from soil weight of S ' (may not be . 120 Ib/ftT In this case, 1536 appears ' \ J required) ' opposite120 Ib/ft® and 8 ft — height of Figure 4 ' . cover. This represents the equivalent prism load for the combined (dead and Foundation Initial backfill .. ■live) load given above. Now enter Initial backfill begins above the ' Preparation is only required when the maximum long-term deflection chart springline of the pipe to a plane-6 inches trench bottom is unstable. Any; ' (Figure 2) for Class III bedding foundation that will support a rigid pipe to 12 inches above the pipe. classification, 75% density, and 8 ft Compacting soils to levels above the without causing loss of grade or flexural of cover, and deterrhine if the maximum springline gives little additional side breaking of pipe will be more than long-term deflection of 772% is exceeded.

Z The green color code shows it will not exceed 772%. This is true for either Series 10 or Series 46. adequate for PVC pipes.

Bedding . . ' The bedding directly underneath the ' support.

Most of the support is accomplished by compacting the soil surrounding the c pipe is required only to bring the trench lower half of the pipe. In working with these charts, it becomes ' bottom up to grade. It should not be so apparent that: , thick or soft that the pipe will settle and Caution: If.hydro-hammers are used to lose grade. The purpose of the bedding prepare the bedding and backfill for the 1. Soil density in .the pipe zone plays a is to provide uniform longitudinal support road surface, they should not be used greater role than soil type in the control of the pipe, y within 3 feet of the top of the pipe and - ' of deflection in buried flexible conduits. then only if the pipe zone soil density . “ . Haunching has been previously compacted to a ."2. The amount of def lection Is . ' ......The haunching area is the most minimum 85% standard Proctor density. independent of pipe size, providing all important in terms of limiting the f pipe sizes are a stiffness of F/Ay 10 psi deflection of a flexible pipe. This is the (Figure 2) or F/Ay 46 psi (Figure 3). area that should be compacted to the Note pipe size does not appear in the Proctor densities shown in charts on chart for maximum long-term deflections. page 7.

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NYC-WTC_000165048