Technical Guidelines for Geomembrane Application in Fish Pond Seepage Prevention

1. Geomembrane Selection Criteria
   1.1 Material Properties Comparison:

• HDPE Geomembrane: Superior impermeability (permeability coefficient<1×10⁻¹³ with="" exceptional="" chemical="" resistance="" ph="" 2-14="" .="" demonstrates="" tensile="" strength="" 25mpa="" and="" retains="" uv="" after="" 10-year="" exposure.="" recommended="" for="" large="" ponds="">1ha) or chemically challenging environments.

• LLDPE Geomembrane: Balanced performance with 15-20% elongation capacity, ideal for moderate-sized ponds (0.5-1ha) experiencing<5cm differential settlement.

• PVC Geomembrane: Features excellent weldability (joint strength ≥90% parent material) but requires environmental impact assessment due to plasticizer migration risks.

1.2 Thickness Specification Matrix:

2. Subgrade Preparation Protocol
   2.1 Geotechnical Requirements:

• Surface roughness: ≤20mm deviation per 3m straightedge

• Compaction: ≥95% Standard Proctor density (SPD)

• Slope gradient: 2:1 (H:V) maximum for geomembrane stability

2.2 Drainage System Configuration:

• French drains: 300mm×300mm gravel-filled trenches with perforated pipes (DN100)

• Collection wells: Minimum 1.5m depth with sump pumps (Q≥5L/s)

3. Installation Methodology
   3.1 Deployment Procedure:

• Unrolling technique: Controlled deployment using spreader beams

• Temperature constraints: Install between 10-35°C to prevent thermal expansion issues

• Temporary anchorage: Sandbag weights at 2m intervals (5kg/m² minimum)

3.2 Seaming Techniques:

• Hot Wedge Welding:

• Temperature profile: 280-320°C (HDPE)

• Seam width: 10cm±2mm

• QC testing: 100% air lance testing + 10% destructive sampling

• Extrusion Welding:

• For complex geometries

• Fillet weld thickness ≥1.5×geomembrane thickness

4. Protection Systems
   4.1 Armor Layer Design:

• Standard protection: 300mm clay layer (k≤1×10⁻⁷ cm/s)

• Enhanced protection: Nonwoven geotextile (500g/m²) + 150mm sand layer

4.2 Operational Safeguards:

• Access control: Dedicated walkways with geotextile underlay

• Maintenance schedule:

• Monthly visual inspections

• Annual leak detection surveys (electrical method)

• 5-year comprehensive integrity assessment

5. Performance Monitoring
   5.1 Key Metrics:

• Seepage rate: ≤0.5L/m²/day (measured through water balance)

• Deformation monitoring: Geodetic survey (≤3mm/yr movement tolerance)

5.2 Failure Mitigation:

• Puncture repair: Patch size = 10×defect diameter

• Seam rehabilitation: 15cm overlap with dual-track welding

Technical Note: For saline environments, specify carbon black-loaded HDPE (2-3% content) with antioxidant additives. In seismic zones, incorporate 10% extra material for stress relief folds.

Best Practice Tip: Implement RFID tags at 20m intervals for lifetime performance tracking and warranty validation.

This guideline complies with ISO 12958 (geosynthetics) and FAO aquaculture standards, ensuring 20+ year service life when properly executed.