Pipe/Soil Stiffness Ratio Effect on Flexible Ipe Buckling Threshold

Abstract

Several types of low stiffness flexible pipe have been introduced in he United States in the past 10 years. Because of its extremely low pipe stiffness, very stiff embedment soil is required to limit pipe deflection to a reasonable alue. This stiff embedment often consists of mechanically compacted crushed rock laced in shallow lifts. Unless this pipe is backfilled under near laboratory conditions, nstallation and compaction forces result in “bulges” or “flat spots” in the nstalled pipe. Often, these shapes are such that the buckling load which the pipe an withstand is reduced to as little as 10% to 20% of the calculated buckling esistance of an elliptically deformed pipe. Six buckling cases, two of thermoplastic ipe, three involving thermoset plastic, and one of metal pipe, are discussed.