Construction of Geotextile Anti-Seepage Embankment Dams: Materials, Parameters, and Methodology

Geotextile-lined embankment dams represent a cost-effective and reliable solution for water retention, tailings storage, and flood control. Utilizing synthetic geomembranes as a primary barrier, these structures offer superior impermeability compared to traditional compacted clay cores. This article outlines the key materials, technical parameters, and a step-by-step construction sequence for a typical geotextile anti-seepage dam.

1. Key Materials and Technical Parameters

The primary sealing element is a geomembrane, typically made from High-Density Polyethylene (HDPE) or Linear Low-Density Polyethylene (LLDPE) due to their excellent chemical resistance, durability, and low permeability. A cushion geotextile is often placed beneath, and a protective layer above, the geomembrane.

Table 1: Typical Material Parameters for Geomembrane Liner System

2. Construction Workflow

The success of the project hinges on meticulous preparation, careful installation, and rigorous quality assurance.

Phase 1: Subgrade Preparation

1. Excavation & Compaction: The dam's upstream slope and foundation area are excavated to stable, competent soil. All sharp objects, rocks >20mm, and vegetation roots are removed.

2. Grading: The subgrade is graded to design slope (typically between 2.5:1 to 4:1, H:V) and smoothed. Tolerances are strict, usually requiring no sudden changes >20mm over a 3m span.

3. Quality Control: The prepared subgrade is compacted to ≥95% of Standard Proctor Density and inspected for uniformity, smoothness, and moisture content.

Phase 2: Geosynthetic Installation

1. Cushion Geotextile Deployment: Rolls are deployed up the slope, with overlaps of 150-300mm. Temporary sandbags secure the sheets.

2. Geomembrane Deployment: Rolls are unrolled perpendicular to the slope's centerline. Panels are laid loosely to accommodate thermal expansion/contraction, avoiding tension during placement.

3. Scanning: The critical step. Adjacent panels (min. 150mm overlap) are joined using dual-track hot wedge welders on slopes and extrusion welders for details, patches, and repairs. Every linear meter of seam is tested.

4. Seam Testing: Non-Destructive Testing (NDT): Air pressure channel testing on dual welds. Destructive Testing (DT): Samples are cut from seam ends daily and tested for peel and shear strength in a lab.

5. Protective Layer Placement: Upon approval of all seams, a layer of cushion geotextile is placed over the geomembrane. Subsequently, a carefully placed free-draining soil layer (e.g., 300-500mm of sand/gravel) is placed via low-ground-pressure equipment to shield the liner from overlying rip-rap or fill.

Phase 3: Anchorage & Final Closure

1. Anchor Trench: The geomembrane and geotextiles are securely placed into a prepared anchor trench at the dam crest and upstream toe, backfilled with compacted soil.

2. Appurtenances: Pipes and structures penetrating the liner are sealed using pre-fabricated geomembrane boots and extrusion welding, followed by rigorous testing.

3. Cover Soil Placement: The final upstream cover soil or rockfill is placed in controlled lifts, ensuring no equipment directly operates on the exposed geosynthetics.

Phase 4: Quality Assurance & Documentation
Construction Quality Assurance (CQA) is continuous. A dedicated CQA team oversees material certification, subgrade preparation, scanning, testing, and final coverage. As-built drawings, welding logs, test reports, and repair records are compiled into a final project dossier.

3. Key Considerations for Success

• Weather: Avoid installation during high winds, rain, or extreme temperatures.

• Material Protection: Store geosynthetics away from UV exposure and damage.

• Seam Integrity: This is the most critical activity. Only certified welders should perform this task.

• Damage Inspection: The liner must be inspected for cuts or punctures both before and after the placement of the protective layer.

By adhering to specified material standards and a disciplined, monitored construction流程, geotextile-lined embankment dams provide a durable, high-performance hydraulic barrier with a service life exceeding decades.