HDPE geomembrane is a critical component of the waterproofing system in hydropower projects. Its construction quality directly impacts impermeability performance and long-term durability. Below is a detailed guide covering construction procedures, technical requirements, and solutions to common issues.
1. Construction Process
(1) Preparation Phase
Site Survey & Design Review
Verify design drawings, geomembrane specifications (thickness, material grade), and slope stability requirements.
Check subgrade conditions (e.g., rock protrusions, drainage systems).
Material Inspection
Ensure compliance with standards (e.g., ASTM GM13, GRI-GM17).
Test key properties: tensile strength, puncture resistance, and carbon black content (for UV protection).
Subgrade Preparation
Remove sharp rocks, roots, and debris.
Compact soil to ≥90% density; apply a protective geotextile (if required) to prevent punctures.
(2) Geomembrane Installation
Unrolling & Positioning
Deploy rolls along slopes or floors with minimal wrinkles.
Allow 1.5–2% slack for thermal expansion/contraction.
Welding & Seaming
Primary Method: Hot Wedge Welding (dual-track for quality assurance).
Secondary Method: Extrusion Welding (for repairs or complex corners).
Seam overlap: ≥10 cm; test seams via air pressure/spark testing.
Anchoring
Fix edges in anchor trenches (depth: ≥50 cm) or with ballast (concrete blocks).
(3) Post-Installation Inspection
Non-Destructive Testing (NDT)
Use spark testing (for conductive geomembranes) or vacuum testing (for seams).
Destructive Testing
Cut samples for peel/shear strength tests (per ASTM D6392).
2. Key Technical Considerations
Slope Installation
For slopes >1:3, use textured geomembranes to enhance friction.
Temporary sandbags or ropes prevent slippage during welding.
Temperature Control
Avoid welding below 5°C or above 40°C; adjust welding speed accordingly.
Drainage Integration
Install geocomposite drainage layers beneath geomembranes (if required).
3. Common Challenges & Solutions
| Issue | Solution |
|---|---|
| Wrinkles/Folds | Re-stretch and secure with sandbags; avoid sunlight exposure before fixing. |
| Seam Failure | Re-weld with extrusion welding; apply sealant for minor gaps. |
| Puncture Damage | Patch with HDPE patches (round edges, 10 cm larger than damage). |
| UV Degradation | Use UV-stabilized geomembranes or cover with soil/ballast. |
4. Case Application
Three Gorges Dam (China): HDPE geomembrane used in reservoir lining and spillway channels.
Pumped Storage Plants: Installed in upper/lower reservoirs to minimize leakage.
5. Conclusion
Proper installation of HDPE geomembrane ensures long-term waterproofing in hydropower projects. Critical steps include:
✔ Strict subgrade preparation
✔ Precision welding & seam testing
✔ Slope stability measures
✔ Post-installation QA/QC
For large-scale projects, third-party inspection is recommended to validate compliance with ASTM/ISO standards.
Would you like details on specific welding parameters or repair techniques?
