design - polypipe.com.au

1 Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe SystemsdesignTrench DesignMinimum CoverThe recommended minimum coverdepths for Vinidex PE pipes are listed inTable cover depths are indicative only,and specific installations should beevaluated in accordance with AS/NZS2566 - Buried Flexible minimum cover depths listed maybe reduced where load reductiontechniques are used, such as loadbearing beams, concrete slabs, conduitsleeves, or increased WidthsIn general practice, the trench widthshould be kept to the minimum thatenables construction to readily to Figures and trench width used with PE pipe maybe reduced from those used with otherpipe types by buttwelding, orelectrofusion jointing above ground, andthen feeding the jointed pipe into thetrench.

2 Similarly, small diameter pipe incoil form can be welded or mechanicallyjointed above ground and then fed intothe minimum trench width should allowfor adequate tamping of side supportmaterial and should be not less than200mm greater than the diameter of thepipe. In very small diameter pipes thismay be reduced to a trench width oftwice the pipe ConditionCover over Pipe Crown (mm)Open country300 Traffic LoadingNo pavement450 Sealed pavement600 Unsealed pavement750 Construction equipment750 Embankment750 Table Minimum CoverSide SupportMaterial used for side support shouldcomply with the requirements of thebedding side support material should beevenly tamped in layers of 75 mm forpipes up to 250mm diameter, and 150mm for pipes of diameters 315mm should be brought evenly tothe design value required by AS/NZS2566 for the specific the sidefill has been placed andcompacted as required over the top ofthe pipe, backfill material may be placedusing excavated backfills should not be used as adump for large rocks, builders debris.

3 Orother unwanted site maximum trench width should berestricted as much as possible,depending on the soil conditions. This isnecessary to reduce the cost ofexcavation, and to develop adequate wide trenches or embankmentsare encountered, then the pipe should beinstalled on a 75 mm layer of tamped orcompacted bedding material as shownon the cross section diagrams. Wherepossible a sub trench should beconstructed at the base of the maintrench to reduce the soil loadsdeveloped. AS/NZS 2566 provides fulldetails for evaluating the loads developedunder wide trench Pipes should be bedded on acontinuous layer, 75 mm thick, ofmaterials complying with the followingrequirements: Sand, free from rocks or other hardor sharp objects retained on sieve.

4 Gravel or crushed rock of suitablegrading up to a max. size of 15mm.. The excavated material, free fromrocks and broken up such that itcontains no clay lumps greater than75mm which would prevent Warehouse Group Pty 1300 661 417PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Systems PE Pipe Trench ConditionFigure Trench ConditionAllowable BendingRadiusVinidex PE pipes are flexible inbehaviour, and can be readily bent in general terms, a minimum bendingradius of 33 x outside diameter of thepipe (33D) can be adopted for PE80C,and PE100 material pipes, whilst a radiusof 20 x outside diameter of the pipe(20D)

5 Can be adopted for PE63, andPE80B material pipes during flexibility enables PE pipes toaccommodate uneven site conditions,and, by reducing the number of bendsrequired, cuts down total job certain situations, the designer maywish to evaluate the resistance to kinkingor the minimum bending radius arisingfrom strain limitation. The long termstrain from all sources should not (4%).Rk=SDR (SDR-1) min100mm minDBedding75mm min100mmmin100mmminBedding75mm minWhen bending pipes there are twocontrol conditions:1. Kinking in pipes with high High outer fibre strain in highpressure class pipes with low condition 1 The minimum radius to prevent kinking(Rk) may be calculated by:For condition 2 The minimum radius to prevent excessstrain (Re) may be calculated by:where = outer fibre strain(maximum allowable = )D = mean Di (mm)RDe=2 Irrigation Warehouse Group Pty 1300 661 417