Geomembrane

The installation of geomembrane must strictly comply with the Technical Code for Application of Geosynthetic Materials (GB/T 50290-2014) and product technical requirements. It mainly centers on five core links: “foundation control → membrane laying → connection and reinforcement → quality verification → protective backfilling”. The key professional points are as follows:
1. Foundation Pre-treatment (Core Premise)
Foundation Cleaning: Thoroughly remove gravel, grass roots, sharp debris (hard objects with particle size > 5mm must be eliminated) from the construction surface to prevent membrane puncture. For local potholes, level them with graded sand and gravel (silt content < 3%), and ensure the compaction degree reaches over 93% (light compaction standard).
Slope Treatment: When the slope gradient > 1:2.5, anti-slip steps (width 30-50cm, height 15-20cm) shall be built; for vertical slopes, anchor trenches (depth 50cm, width 40cm) shall be set, and graded sand and gravel shall be filled in the trenches to prevent membrane sliding.
Protective Layer Laying: If the foundation is a rigid interface such as sand-gravel or concrete, first lay short-fiber needle-punched geotextile with weight ≥ 300g/m² (lap width 15cm) as a membrane buffer layer to avoid direct friction damage between the membrane and the rigid foundation.
2. Membrane Laying (Key Control)
Laying Direction: Priority shall be given to laying along the long-axis direction of the terrain to reduce the number of joints. When laying on slopes, unfold the membrane from top to bottom; dragging from the bottom of the slope is prohibited to avoid membrane stretching and deformation (elongation rate shall be controlled within 5%).
Slack Control: Reserve slack according to ambient temperature – 3%-5% reserve at 20-30℃, and 8%-10% reserve when temperature < 10℃ – to prevent weld cracking due to low-temperature shrinkage. After laying, temporarily fix the membrane with sandbags (15-20kg per bag) at intervals of 2-3m to avoid displacement by wind.
Lap Requirements: The flat lap width ≥ 10cm, and the slope lap width ≥ 15cm; joints of adjacent membrane rolls shall be staggered (staggered distance ≥ 50cm), and “cross-shaped” joints are prohibited to reduce leakage risks.
3. Connection and Reinforcement (Core Process)
Welding Process (Mainstream Method for HDPE/LDPE Membranes)
Equipment Selection: Use a double-track hot-melt welding machine (welding temperature 180-220℃, traveling speed 1.5-2.5m/min), with a hot air gun for edge treatment. When the membrane thickness > 1.5mm, double-track welding shall be adopted (weld width 10-15mm, with a detection air channel left in the middle).
Pre-welding Test: Before formal construction of each batch, conduct a test weld under the same working conditions (test weld length ≥ 1m), and start formal construction only after passing the tensile test (weld tensile strength ≥ 80% of the base material).
Bonding Process (For Flexible Membranes Such as EVA/ECB)
Use special two-component polyurethane adhesive (curing time 24h). First, clean the lap surface (wipe with acetone to remove dirt), apply adhesive with thickness 0.8-1.2mm, let it stand for 5-10min, then bond and roll repeatedly with a rubber roller (pressure 0.3-0.5MPa) to ensure no air bubbles in the adhesive layer.
4. Quality Verification (Mandatory Inspection Link)
Weld Inspection: Adopt the “air inflation test method” for double-track welds – insert the test needle into the weld air channel, inflate to 0.25MPa, and maintain pressure for 5min; a pressure drop ≤ 0.02MPa is qualified. For single-track or bonded joints, use the “vacuum test method” – cover the joint with a vacuum hood (negative pressure 0.02MPa), and no air bubbles observed is qualified.
Appearance Inspection: Check that the membrane has no damage or wrinkles (local wrinkle area ≤ 0.2m²), no edge warping or degumming at joints, and the membrane in the anchor trench is firmly fixed (no loosening).
Sampling Inspection: Randomly select 3 joints per 1000m² for tensile testing; if unqualified, double the sampling volume; if still unqualified, rework the joints of this batch.
5. Protection and Backfilling (Final Guarantee)
Temporary Protection: Complete covering within 24h after the laid membrane passes inspection; the exposure time ≤ 48h (to avoid UV aging). Use geotextile with weight ≥ 500g/m² for temporary covering, fixed at intervals of 1.5m.
Backfilling Requirements: Backfill with fine-grained soil (particle size < 20mm, silt content 15%-25%), in layers (each layer thickness 20-30cm), with compaction degree ≥ 90%. Heavy machinery is prohibited from directly rolling the membrane during backfilling; first compact the surface soil with a light roller (≤ 5t), then use heavy machinery for operation.
Anchorage Treatment: Fill the anchor trench with graded sand and gravel (compaction degree 93%), and seal the top with a concrete cover plate (thickness 10cm) to prevent membrane falling off due to rainwater scouring.