Minimum-Risk Bedding for Flexible Drain Pipes

The soil bedding for nonpressurized buried flexible pipes is critical for minimum-risk performance. Lack of adequate bedding reduces the strength of the pipes by a factor of 2 or more. To compensate, pipes must have high strength, at increased cost, in order to avoid the risk of failure. Structural performance and performance limits are compared for plastic drainpipes with a variety of beddings. Compared to a flat bedding, the risk of failure is greatly reduced by shaping the bedding. Shaped beddings perform essentially as well as full-contact embedment with select granular soil. Tests and analyses show that a 90° V-groove bedding that supports and aligns the pipe performs nearly as well as a 180° form-fit circular groove or a full-contact embedment of select soil. Comparison of beddings is important in the design and installation of drainpipes in order to assure minimum risk of failure.