the report covers work carried out in the cambridge university engineering department under a transport and road research laboratory research contract to study the behaviour of buried flexible pipes. the work consists of a series of centrifuge experiments conducted on very flexible model pipes buried at shallow depth in uniform dense sand, to examine the validity of ring compression theory under the combined action of self weight of the backfill and surface loading. tests were carried out on model pipes made from steel and plastic having different effective stiffness to study the influence of this factor on the reductions in load which takes place due to arching. a comparison is given of the calculated pressures and measured pipe stresses from which load reduction factors are derived. the ring compression theory is shown to be valid for model pipes in wide trenches or under embankments when subjected to combined surface and backfill loadings. the results illustrate that the load reduction factor is influenced by the intensity of surface loading and by the depth of embedment and is greatly dependent on the effective stiffness of the pipe.(a)

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