FlowTex GSC NW Nonwoven Sand Containers

Site preparation. - Excavate to firm base material over the full length of the revetment section. Remove rocks, stumps, root systems and protrusions and backfill the resulting cavities with sand compacted flush - irregular base surfaces prevent uniform bag contact and create stress concentrations under wave loading. Shape the slope to the design batter angle, toe elevation, crest elevation and rear taper before any container is placed; the profile cannot be reshaped afterwards without disturbing installed work. Establish setting-out pegs at toe and crest along the full length, with intermediate references at each end of the working

Underliner. - Lay a nonwoven filter geotextile over the prepared section, covering the full slope length and the base of the toe trench, before any container is placed. It separates the structure from native soil to prevent fines migration under pore-pressure cycling, and provides a consistent bearing surface for the first course. Lap panels down the slope in a shingle pattern, upper panel beneath lower so downslope flow passes over the joint. Minimum overlap 500mm on stable subgrades, 1,000mm on soft or variable ground. Where differential settlement is expected, sew or thermally bond the overlaps rather than free-lapping.

Toe embedment. - Placement begins at the toe and proceeds up the slope. Set the first container along the front line with its longer dimension parallel to the shoreline - this establishes the datum for every course above, and any misalignment introduced here propagates upward. Embed the toe container to a minimum of 1.8 times the significant wave height below design water level, per USACE Coastal Engineering Manual and CIRIA Rock Manual guidance. Toe scour removes lateral support and drives forward rotation and progressive collapse; inadequate embedment is the most commonly documented cause of geotextile revetment failure. Verify against project design wave height before placing any course above the toe.

Filling and closure. - Fill to approximately 80% of theoretical volumetric capacity. Overfilling prevents units conforming to each other and destroys interlock; underfilling produces excessive deformation and creates voids that concentrate hydraulic pressure at joints. Fill must be clean, well-graded sand free of sharp debris, organic contamination and material finer than the container O90. Fill bottom corners fully without creasing or folding before closing. NW40 through NW1350 are filled by hopper or mechanical equipment; NW1800 and NW4000 may be hydraulically filled in place. All closures are double-seamed - a straight pass followed by a zigzag or overlock second pass in UV-stabilised yarn. Single straight-seam closures are not compliant for structural coastal applications.

Stacking and compaction.- Lay successive courses in stretcher bond, each container offset half a bag length from the course below. Never stack in vertical columns: continuous vertical joints open progressively under repeated hydraulic loading, where staggered placement distributes wave-induced force across multiple units. After a minimum run of three containers, level and compact the course with the back of the excavator bucket or a plate compactor before the next is placed. Double-layer configurations provide approximately 17% greater stability than single-layer of the same grade under equivalent wave conditions. Check face alignment against setting-out pegs at every course to prevent progressive drift.

Crest, backfill and sign-off. - Crest containers take wave run-up and overtopping in addition to direct attack; place them last and with the greatest care. Bench the rear profile to receive each successive course, folding the underliner back over completed sections and overlapping at each bench to prevent flanking flow behind the structure. Complete the crest fill, taper off with specified compacted backfill to design elevation, and level the exposed face with sand. Photographic records are taken of each course before the next is placed under IAGI-aligned QA/QC, producing a verifiable installation record for the full structure depth.