Interface Relationship

In typical composite liner systems (e.g., municipal solid waste landfills, hazardous waste containment sites), the bottom-to-top structural sequence is generally:

There is no chemical bonding or welding between the GCL and the HDPE geomembrane. Instead, their interaction relies on:

• Frictional Interface Contact: Once the GCL is deployed and inspected, the HDPE geomembrane is installed directly over it, ensuring continuous, intimate contact between the two layers.

• Independent Seaming: The GCL seams are sealed with bentonite powder/paste, whereas the HDPE geomembrane seams are hot-wedge or extrusion welded.

• Synergistic Hydraulic Barrier: The GCL acts as a secondary barrier capable of self-healing minor punctures, while the HDPE geomembrane functions as the primary barrier. Together, they create a high-integrity composite lining system.

Note: When using film-laminated GCLs (GCL-OF), the upper surface of the GCL features an integrated HDPE film. In this case, the interface between the primary HDPE membrane and the laminated GCL film must be executed strictly according to design specs, rather than default standard GCL overlap methods.

GCL Overlapping and Seam Sealing

Standard GCL panels are connected via mechanical overlapping (no thermal welding or stitching), relying on the hydraulic swelling of sodium bentonite to create a self-sealing joint:

• Overlap Width: Industry standards mandate an overlap width of 250 ± 50 mm (10 ± 2 in).

• Bentonite Sealant Placement: Apply granular or powdered sodium bentonite sealant along the lower panel’s overlap margin (approx. 150 mm from the edge). The sealant strip should be roughly 50 mm wide, applied at a rate of $ge 0.5text{ kg/m}$ ($ge 0.35text{ lb/ft}$).

• Slope Details: Avoid horizontal overlaps on side slopes; anchor panels in top-of-slope anchor trenches. Always overlap in the direction of flow (shingle arrangement) and stagger transverse seams (brick pattern). Avoid four-corner "cross" intersections.

• High Wind or Dry Conditions: Mix the bentonite powder with equal parts clean water to form a bentonite paste. This prevents wind loss during application.

• Pipe Penetrations: Cut a square GCL collar sized to the pipe diameter + 500 mm (20 in). Slip the collar over the pipe and fill the annular space around the penetration with powdered bentonite seal.

Critical Requirement: Deployed GCL must be covered with the HDPE geomembrane on the same day. Halt all installation during rain or snow, and temporarily cover deployed panels. If the GCL hydrates prematurely before overburden placement, seam integrity is compromised.