Landfill Liner System: Design & Installation
Modern solid waste landfills rely on a composite liner system — GCL as the hydraulic barrier, HDPE geomembrane as the primary impermeable layer, and a geonet drainage layer above it. This guide explains each layer and the installation sequence that makes the system work.
1The Composite Liner System, Layer by Layer
A typical landfill bottom liner (from bottom to top):
Fig. 1 Typical landfill bottom liner build-up: GCL → HDPE → protection geotextile → drainage geonet (schematic).
| Layer | Function | Typical spec |
|---|---|---|
| GCL (geosynthetic clay liner) | Secondary hydraulic barrier, self-sealing | Na-bentonite ≥ 4500 g/m², permeability ≤ 5.0×10⁻¹¹ m/s |
| HDPE geomembrane | Primary impermeable layer | 1.5–2.0 mm smooth, GB/T 17643 |
| Protection geotextile | Puncture protection over HDPE | 400–600 g/m² nonwoven |
| 3D drainage geonet | Leachate collection and removal | HDPE core 5–8 mm, double-sided fabric |
2Subgrade Preparation
- Compact the subgrade and remove stones above 10 mm; roll smooth so no sharp protrusions remain.
- If specified, place a 300 mm compacted clay layer below the GCL and proof-roll it before liner placement.
- Grade the floor with 1–2% slope toward the leachate collection sumps.
3Installing the GCL Layer
- Unroll GCL panels with 150–300 mm overlaps; keep the overlap dry and dust-free.
- Apply granular sodium bentonite (about 0.4 kg per linear metre) along the overlap, then seal with the factory lap tape — this is the most common on-site failure point.
- Prevent premature hydration: do not let rain soak the rolls; cover laid panels quickly or install on a dry day. Hydrated GCL is nearly impossible to repair properly.
- On slopes, lay panels parallel to the slope and anchor at the top before placing HDPE above.
4Installing the HDPE Geomembrane
- Place HDPE panels with ≥ 100 mm overlap; weld with a double-track hot wedge welder after trial welds (temperature 380–420 °C).
- Every weld seam gets an air-pressure test (0.2 MPa, 5 min hold, drop < 20%) through the 50 mm channel between the weld tracks.
- Repair any scratches or punctures with extrusion weld + patch of the same material, then vacuum-test the patch.
- Anchor the HDPE in the perimeter trench together with the GCL (anchor trench ≈ 800 mm × 800 mm on large cells).
5Drainage & Protection Layers
- Place the protection geotextile (400–600 g/m²) directly on the welded HDPE before the drainage geonet, so the geonet ribs never touch the membrane.
- Lay the 3D drainage geonet with overlaps and connect to the leachate collection pipes and sumps.
- Backfill carefully — no tracked machinery directly on the geonet; use light equipment with rubber tyres over a temporary cover layer.
6QC Checklist
- GCL overlap bentonite sealing recorded and photographed per panel.
- HDPE weld map drawn, every seam numbered and test result logged.
- Leachate drainage slope verified by survey before waste placement.
Practical tip: on large cells, buy GCL and HDPE widths that match — e.g. 6 m GCL rolls with 6 m HDPE panels reduce total seam length by roughly one third, cutting welding labour and leak risk together.
Planning a Landfill Liner?
Send the cell area and design spec — we supply GCL, HDPE, geotextile and drainage geonet with batch test reports, and quote within 24 hours.
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