Maximum Fill Height for HDPE Corrugated Pipe

HDPE corrugated pipe is more economical than steel or concrete corrugated pipe in culvert applications. Its corrugated pipe fill height capacity, meaning its strength under embankment loads, can be analyzed using soil-structure interaction (SSI), so the maximum fill height can be determined by considering pipe size, corrugation geometry, backfill quality and service life.

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The pipe sizes in the study are standard 4 inch, 6 inch, 8 inch, 10 inch, 12 inch, 15 inch, 18 inch, 24 inch and 30 inch pipes. Each pipe size can be combined with corrugation area, backfill quality and service life. These combinations can be entered into the CANDE software (l). The analysis results must meet AASHTO standards. The design fill heights are shown in the following table (after Katona).

Fill height for HDPE corrugated pipe

Symbol S denotes short-term (temporary) pipe design, while symbol L denotes long-term (sustainable) pipe design for a 50-year design life.

Fair and good quality soil can be determined from the Duncan soil model: silty clayey sand at 85% compaction is classed as fair, while silty clayey sand at 100% compaction is classed as good. These Duncan parameters are shown in the following table.

Fill height for HDPE corrugated pipe

Note that the maximum height table above (after Katona) applies when the density of the backfill soil is S = 18.85 kN/m3. If the actual backfill density is S*, the fill height H* can be determined with the following formula:

Fill height for HDPE corrugated pipe

For a design life between 0.05 years and 50 years, the design height can be determined with the following formula

Fill height for HDPE corrugated pipe

where

HI is the fill height for the long term (50 years)

t is the design time (in years)

m is the exponent

Hs is the design fill height for the short term (0.05 years)

Ht is the fill height at a given year

Example:

An ID 600 pipe has a corrugation area of 7.6 mm2/m and is designed for a 50-year service life. It is backfilled with well-graded silty sand at 85% compaction. The density of this backfill is 20.42 kN/m3. Determine the maximum allowable fill height:

Solution:

From the correlation table, for SM soil at 85% compaction, r = 0.5.

Using the table (after Katona):
Hf = 4.6 m (fair soil, long term)
Hg = 9.6 m (good soil, long term)

The design fill height for r = 0.5 is 7.1 m

For a density of 20.42 kN/m3, the corrected design fill height is 6.5 m (for a 50-year design life)

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