What are the laying methods for geotextiles

What are the laying methods for geotextiles?

Basic laying method: Manual rolling laying is the primary method. Direct dragging by machinery is strictly prohibited. Keep the fabric flat with a small relaxation allowance (1%–3%), do not stretch it tight.

I. Three core jointing methods

 Lap joint

Practice: Overlap two fabric panels directly, upper panel covering the lower one, laid in the direction of water flow or filling advance.

Overlap width: Normally ≥20 cm; ≥30–50 cm for soft foundation, underwater and slope works.

Fixation: Sand bags or U-shaped nails for temporary pressing to avoid displacement caused by wind or backfilling.

Application: Roadbed separation, geomembrane protection layer, general slope protection and temporary works (most commonly used for staple fiber geotextiles).

Advantages: Fast construction, low cost. Disadvantages: Low load-bearing capacity, not suitable for high-reinforcement or long-term exposed areas.

 Sewing joint

Practice: Use a portable special geotextile sewing machine for continuous double-lock stitching; spot stitching is not allowed. Overlap width: 10–15 cm.

Sewing thread: UV-resistant and corrosion-resistant polyester thread, single thread tensile strength ≥60 N.

Application: Filament geotextiles, landfills, hydraulic projects and permanent works with high reinforcement requirements. Preferred when hot melting cannot be performed on rainy and wet days.

Advantages: High joint strength and good integrity.

Hot air welding

Practice: Heat the fabric edges with a hot air gun, then press and bond after melting. Overlap width ≥10 cm.

Application: Spun-bond filament geotextiles; protective layers for anti-seepage systems of landfills and sewage ponds. Not suitable for polypropylene staple fiber (easy to burn and scorch).

Advantages: Impermeable and high integrity. Disadvantages: Cannot be constructed under low temperature, rain or snow.

 II. Laying processes by construction position

1. Laying on flat base (roadbed, storage yard, landfill bottom)

Base preparation: Remove sharp stones and tree roots; level uneven areas with fine sand.

Sequence: Unroll along the longitudinal direction of the roadbed, minimize joints; stagger joints and avoid concentrating them on the same cross-section.

Cover with fill material promptly after laying. Vehicles are forbidden to drive directly on exposed geotextiles to prevent puncture.

2. Slope laying (river embankment, mountain slope protection)

Principle: Anchor at the slope crest first, then lay from top to bottom; laying from bottom to top is not permitted.

Set anchor trench at slope crest (burial depth ≥30 cm, backfill and compact). Fix on slope surface with U-shaped nails or sand bags at spacing of 1–2 m.

Minimize horizontal joints on slopes; horizontal joints shall be ≥1.5 m away from the slope toe to avoid stress concentration zones.

3. Laying matched with geomembrane (one geotextile one geomembrane / two geotextiles one geomembrane)

Geotextile under geomembrane: Adopt lap joint to protect the membrane from puncture by the base.

Geotextile above geomembrane: Sewing or hot air welding is preferred to prevent dislocation between membrane and fabric during backfilling.

4. Underwater / cofferdam laying

Widen overlap width (≥50 cm) and fix in advance to prevent scouring by water flow. Sewing is preferred; simple lap joint shall be used as little as possible.