FR0124

Sept 1990

The objective of the work was to evaluate the short term performance of a uPVC pressure pipe when installed to different standards of workmanship and subjected to surcharge and internal pressure loading under varying conditions.

uPVC pipelines account for approximately 50% of new water mains installation and are installed with granular embedment or as dug material. The work was to determine whether the use of poorly compacted as-dug material as pipe embedment could lead to poor performance of the pipeline, relative to that for specified good practice. A better understanding of pipe performance in relation to installation conditions should lead to reliable and cost effective service performance.

Under exactly similar loading conditions strains induced in the pipeline installed to a standard of poor workmanship were appreciably higher than those for a pipeline installed to a good standard. Induced strains, in all circumstances, were within the short term working limits of the pipeline material. The various loading conditions produced similar deflections for the pipe installed to a good standard of workmanship. This was also the case for the poorly installed pipe. However, deflections were higher in the pipe installed to the lower standard of workmanship.

Further work would be required before a relaxation of current installation specifications could be justified at a technical level.

On the basis of short term results there appears to be scope for increased use of suitable as-dug bedding and surround materials.

The reported work relating to short term installation trials should be formally reviewed in relation to longer term material performance considerations.

The testing was carried out in the WRc test pit facility at Swindon. The performance of the pipeline was assessed with two types of embedment material; l4mm single size aggregate and as-dug clay. These materials were used respectively to install the pipeline to a good and poor standard of workmanship.

Uniformly distributed loading (UDL) was applied to the pipeline through 0.9 metres of cover for both buried tests.

To determine the performance of the pipeline, strain was monitored on a total of 56 strain gauges. In addition vertical and horizontal pipe deformation was monitored in one position on the pipeline.

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