construction and refurbishment of earthen irrigation channel banks

Edge fixing and adequate freeboard provision is necessary to prevent wateroverflowing the top edge and seeping down behind lining, where it can push thelining out or cause slippage failure of the batter slope.The polymeric membranes (HDPE, PVC, PP etc) all require edge fixing which willusually be achieved by an anchor trench on top of both banks along the entire lengthof the channel. The trench needs to be set back at least 0.5 m and preferably 1.0 mfrom the crest and can be rectangular or a triangular cut with a grader blade. It isbackfilled over the liner with the spoil material with nominal compaction. ReferFigure 22.10 and Figure 22.11.1 mGeomembraneBackfill0.3 m0.5 mMaximum Slope 1:2Figure 22.10Typical Anchor trench – rectangular trench1mBackfillGeomembrane0.3m0.5mMaximum Slope 1:2Figure 22.11Typical Anchor trench – V notch22.8.7 Attaching to StructuresThe liner can be terminated at the ends into an anchor trench or with a mechanicalbatten fixing to a concrete structure. ReferFigure 22.12. If the concrete forms part of the new work there are elements whichcan be cast into the concrete surface for subsequent welding of the membrane.At structures the geomembrane can be bonded to cut-offs. It may not be necessary todirectly connect the geomembrane to structures where a satisfactory seal can beachieved using an anchor trench. The geo membrane can be laid against the structureand backfilled with impervious clay material to seal the liner-structure interface.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 22-56