Geotextile for slope protection, five roles across the face.
On a Malaysian slope, geotextile is rarely the headline system: it is the silent partner that makes every headline system work longer. Filter behind geocell facing. Separator below rip-rap or coir mat. Basal mat at the slope toe. Reinforcement in steep RSS wrapped lifts. Cushion above geomembrane on landfill closure caps. Five roles, five spec families. Getting it right adds years of life to soil nailing, shotcrete, geocell, rock netting, retaining walls, and the slope itself; getting it wrong is a 5-20x rectification penalty within a few wet seasons. We supply via Starwall (sole STRATA distributor) and install with CIDB G7 slope crews nationwide.
Function-first selection, one slope at a time.
1. Filter behind facing systems
Behind geocell facing, behind shotcrete, behind rip-rap, around horizontal drain outlets, around perimeter pipe drains. Lets water out while retaining fines. Always nonwoven (200-300 gsm needle-punched PP for routine; up to 400 gsm where flow rates or fines load are high). AOS sized to subgrade fines (typical 0.10-0.15 mm for Malaysian residual soil). Permittivity at least 10x subgrade permeability.
2. Separator under cover layers
Below rip-rap toe protection, below coir mat or jute mesh for vegetation establishment, below imported topsoil capping. Stops native fines from migrating into the cover layer and the cover from sinking into the soft subgrade. Nonwoven 200-300 gsm typical; heavier (300-400 gsm) below thick rip-rap or where the subgrade is very fine and saturated. Often the same product as the filter role.
3. Basal mat at slope toe
Where the slope toe sits on soft alluvium, peat, or marine clay, a basal mat at the toe carries lateral thrust and prevents bearing-failure rotation. Woven HSR PET 100-400 kN/m at the toe horizon, anchored back into the slope foundation. See our basal reinforcement page for the design framework.
4. Reinforcement in steep RSS lifts
For wrapped-face reinforced soil slopes, the reinforcement at each lift is normally uniaxial PET geogrid; but for wrapped-face geotextile applications (lower-tensile, shorter design life), high-tenacity woven geotextile (60-200 kN/m) is the alternative. Used for embankment widening, plantation embankments on stable subgrade, and lighter slope construction. See RSS page.
5. Cushion above geomembrane (landfill closure cap)
On landfill closure caps the cover-system geomembrane is cushioned above and below with heavy nonwoven (400-1000 gsm) to prevent puncture during cover placement and through service life. Same product family as the landfill base protection. Per FHWA / EPA / BAM 1996 protection-sizing rules. See landfill liner design.
What goes with what.
| Slope system | Geotextile role | Typical grade |
|---|---|---|
| Soil nailing + shotcrete face (cut slope reinforcement) | Filter face behind shotcrete; weep-pipe wrap | Nonwoven 200-300 gsm |
| Geocell slope facing (StrataWeb) | Filter / separator below cells | Nonwoven 200-300 gsm |
| Reinforced soil slope (RSS) wrap-face | Inter-lift wrap (when not using geogrid alone) | Woven 60-150 kN/m |
| Rip-rap toe protection | Separator below rip-rap | Nonwoven 200-400 gsm |
| Coir mat or jute mesh erosion-control face | Separator below cover | Nonwoven 130-200 gsm |
| Horizontal drains (hillside dewatering) | Filter wrap around drain outlet collection box | Nonwoven 200 gsm |
| Retaining wall (gravity, cantilever, MSE) | Filter behind back-of-wall drainage trench | Nonwoven 200-300 gsm |
| Rock netting and rockfall barriers | Separator below toe-protection bund and drainage berm | Nonwoven 200-300 gsm |
| Ground anchors (compound stability) | Filter at any associated drainage outlet | Nonwoven 200 gsm |
| Landfill closure cap (geomembrane plus cover) | Cushion above and below geomembrane | Nonwoven 400-1000 gsm |
For projects with multiple partner systems we deliver a project-wide geotextile specification matrix as part of supply documentation; the right grade in each location, with delivery scheduled to the build sequence.
How to write a slope geotextile spec that works.
Function-first (not weight-first)
The slope geotextile specification starts from the role (filter, separator, basal, reinforcement, cushion), not from a weight target. Weight (gsm) is a downstream output of the function and the loading. Specifying weight without role is the most common error and leads to under-specification on demanding roles.
For filter / separator (the most common)
- Material: nonwoven needle-punched PP.
- Weight: 200-300 gsm typical; 300-400 gsm for thick rip-rap or saturated fines.
- AOS (apparent opening size): sized to retain native fines per BS 6906-2 or ASTM D4751. Typical 0.10-0.15 mm for Malaysian residual saprolite; 0.06-0.10 mm for marine clay; 0.15-0.20 mm for sandy alluvium.
- Permittivity: at least 10x the subgrade permeability per ASTM D4491. Typical 1.5-3.0 per second for standard 200-300 gsm grades.
- Puncture resistance: CBR puncture above 1.5 kN per ASTM D6241 for routine; above 3.0 kN below heavy rip-rap.
For reinforcement (when used as RSS wrap)
- Material: woven high-tenacity PET.
- Wide-width tensile: 60-200 kN/m per ISO 10319; long-term design tensile via BS 8006 reduction factors.
- Elongation at break: 10-15 percent to limit slope deformation.
- Polymer: PET for permanent or long-life applications.
For cushion above geomembrane
- Material: heavy nonwoven PP.
- Weight: 400-1000 gsm per protection-sizing calculation (BAM 1996, FHWA, EPA).
- CBR puncture: above 3.0 kN.
Where this product goes across the country.
1. Hillside township slope works
Cut-slope stabilisation with soil nailing and shotcrete across Klang Valley and Penang hillside developments. Nonwoven filter face behind the shotcrete, weep-pipe wraps, and toe-drainage filter. Standard 200-300 gsm specified on every slope-works package; integrates with our slope reinforcement scope.
2. Highway and expressway slope works
JKR and PLUS cut-slope rectification with rock netting, rockfall barriers, and toe protection. Nonwoven separator under rip-rap toe berms; filter wraps on drainage. Sometimes basal mat at slope toe where the alignment crosses soft alluvial sections.
3. Plantation slope and bench reinforcement
Sabah, Sarawak, Pahang plantation slope work. Geocell vegetated facing with nonwoven underlay, occasional wrap-face RSS construction on benched cuts. Lower-spec geotextile range works well in these less-demanding contexts.
4. Quarry, mine, and earthworks restoration
Bauxite, granite, tin tailings slope restoration under DOE rehabilitation conditions. Nonwoven separator below coir / jute mat erosion-control face; sometimes heavy nonwoven cushion above geomembrane on cap-and-cover restoration projects.
5. Hillside landslide remediation
Post-failure remediation projects (Highland Towers historical context, monsoon failure events in Cameron Highlands and Bukit Antarabangsa). Geotextile in filter, separator, and reinforcement roles depending on the remediation strategy; integrates with our post-landslide remediation scope.
6. Reservoir, pond, and lagoon slope linings
Earth-fill dam upstream face, polishing pond bank protection, retention pond face. Heavy nonwoven cushion above HDPE / LLDPE geomembrane lining (see geomembrane for pond and landfill), plus nonwoven filter wraps at toe drainage.
Field practice that prevents failure.
- Subgrade preparation. Trim slope to a smooth profile, remove root mats and loose material, fill local hollows that could trap water below the geotextile.
- Roll out parallel to slope contours. Geotextile is rolled out across the slope with the long dimension parallel to contours (not down the slope). Overlap adjacent rolls 300-500 mm on dry slopes, 500-1000 mm on wet or soft subgrade. Upper roll overlaps the lower (shingle pattern for runoff).
- Anchor at crest and toe. Geotextile is buried in a key trench at the slope crest (300-500 mm deep, backfilled) and either similarly buried at the toe or weighted by the toe-protection berm. The crest key prevents the entire fabric from sliding down the slope; the toe stops it from peeling up under uplift.
- Pin to slope at intermediate points if needed. On steep slopes (above 1V:1H) or in high-wind sites during the period before cover is placed, pin the geotextile to the slope with steel staples or geotextile pins at 0.5-1.0 m centres.
- Cover promptly. Geotextile exposed to direct sunlight degrades within weeks (UV stabilisation in PP is good but not infinite). Cover (rip-rap, topsoil, shotcrete, geomembrane, geocell) within 2-4 weeks of placement under tropical sun.
- Protect during cover placement. Avoid dropping rip-rap or aggregate from height onto thin nonwoven (use of skips, swing-arm conveyors, or chuted placement); avoid tracked plant directly on the geotextile.
Combined slope scope.
Geotextile →
Product hub.
Woven vs nonwoven →
Selection rule.
Geocell slope stabilisation →
Primary slope-facing system.
Reinforced soil slope →
Full-rebuild slope option.
Slope protection →
Sector page.
Slope reinforcement →
Sector page.
Compare slope surface protection →
Side-by-side selector.
Geotextile filter calculator →
AOS / permittivity sizing.
Slope geotextile spec or partner-system brief?
WhatsApp the slope cross-section, partner system (soil nail, geocell, rip-rap, geomembrane), and design life. Same-day role-mapped grade selection and price. Supply via Starwall, certificate of conformance on every delivery.