STABILITY OF HDPE PIPES UNDER HIGH HEAP LOADS

摘要

Heap and valley leach operations rely on solutionrncollection piping placed within the heap to enhancernboth solution recovery and to assist overall solutionrnmanagement. The most common piping used inrnleaching operations is solid or perforated HighrnDensity Polyethylene (HDPE) pipe and CorrugatedrnPolyethylene pipe (CPE). These pipes are widelyrnused because of their low cost, ease of installation,rndurability, and flexibility.rnThe typical recommended maximum design depthrnof burial for HDPE and CPE pipes is on the order ofrn30 meters (100 feet). However, ore heap heights atrnmany facilities exceed 30 meters and some are nowrnapproaching 180 meters (600 feet) in height. At veryrnhigh ore heap heights, the stability and performancernof HDPE and CPE pipes becomes a critical issue forrnleaching facility design and operation. Failure ofrnsolution collection piping can lead to poor solutionrnrecovery, high hydraulic heads on the liner system,rnand in some cases, unstable ore slopes due to highrnsolution pressures near slopes.rnThis paper presents a review of methods that haverntraditionally been used to evaluate pipe stabilityrnunder high normal loads. A common shortcoming ofrnthese methods is the inability to account forrnbeneficial effects of ore arching around pipes andrnthe time-dependent creep (stress relief) behavior ofrnpolyethylene (PE) materials. A new analyticalrnapproach is developed and presented whichrnincludes the effects of ore arching around pipes andrncreep of PE materials. The results of the newrnapproach show that PE pipes will deform under highrnheap loads, but can remain stable and functional.rnPipe stability is shown to be dependent on the typernof pipe backfill and initial backfill compaction. Thernnew approach represents a useful tool for designingrnapplications for PE pipe under high normal loads.