geotextile tubes coastal protection are tubular containers made from engineered woven geotextile. When hydraulically filled with sand they form dense, load-bearing structures that resist wave erosion, stabilize shorelines and enable controlled land reclamation.
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1. Overview
Geotextile tubes for coastal protection are tubular containers fabricated from engineered woven geotextile. They are hydraulically filled with sand to form compact, structural bodies whose primary functions are to resist wave and wind erosion, reinforce shorelines and shape coastal terrain. Combining high permeability and tensile strength, water drains through the fabric pores while sand is retained to create a stable mass. Compared with traditional rock revetments, these tubes reduce structural weight by over 60% and adapt well to tidal and complex marine conditions. They are widely used in coastal defence projects to reduce settlement and seepage risk.
2. Technical Specifications
| Key Parameter | Value | Test Conditions / Notes |
|---|---|---|
| Diameter | 1.5–5 m | Measured on standard finished tube cross-section |
| Longitudinal tensile strength | ≥ 15 kN/m | Fabric tensile test at ambient temperature |
| Transverse tensile strength | ≥ 12 kN/m | Fabric tensile test at ambient temperature |
| Seam strength | ≥ 90% of bag fabric strength | Peel test of sewn/ bonded seams |
| Filling rate (sand) | 20–30 m³/h | Measured via hydraulic filling system flow monitoring |
| Compaction density | ≥ 8 blows / 30 cm | Measured with heavy dynamic cone penetrometer |
| Seawater immersion resistance | ≥ 72 h | Artificial seawater, salinity 3.5% immersion test |
3. Typical Applications
- Coastal erosion protection: Construct the core of breakwaters in the intertidal zone to resist scouring from currents exceeding 1.5 m/s and reduce shoreline retreat.
- Land reclamation and enclosure: Serve as embankment structures; combined with sand fill they form reclamation bases suitable for mudflats and soft subsoils.
- Harbour revetment reinforcement: Protect quay-fronts from berthing impacts and wave scour.
- Artificial island construction: Used as cofferdam or containment elements to enable rapid formation and long-term stability.
4. Installation & Operation Guidelines
- Pre-installation checks: For every 10,000 m² of incoming material, sample and test one set for tensile strength. Store products covered and shaded to prevent UV degradation. Prepare base to within flatness ≤ 10 cm and remove shells, debris and stones.
- Placement and fixation: For above-water work use sandbags at 1 m spacing to hold edges; for submerged placement insert φ100 mm steel locating piles ≥ 1 m into the base to prevent tube drift.
- Filling procedure: Fill in sequence “corners first, then center”. Single-layer thickness 0.4–0.5 m, target fill ratio 80%–85%. Allow 24 h static consolidation before placing subsequent layers.
- Maintenance: Inspect tube fabrics and seam integrity quarterly; increase compaction inspections after heavy rain events.
5. Frequently Asked Questions
- Q: What causes bag rupture and how to prevent it?
- A: Typical causes are insufficient tensile strength (< 15 kN/m) or construction impacts. Implement incoming material sampling, use soft separators during transport, and have divers confirm the base is free of debris before filling.
- Q: How to handle seam sand leakage?
- A: If leakage ≥ 0.5 m³/h, stop filling immediately. Seal small gaps with 5 cm wide waterproof tape; major seams should be re-stitched (stitch density 10–12 stitches / 10 cm). Refill and allow 24 h static observation.
- Q: What problems arise from insufficient fill compaction?
- A: Compaction < 8 blows / 30 cm can lead to settlement > 5 mm/month. Remedy with high-pressure water jet compaction (≥ 0.6 MPa) or localized tamping with small additive fills.
- Q: How to prevent alignment (axis) drift?
- A: Ensure edge pile embedment ≥ 1.5 m and recheck GPS positioning every 20 m (accuracy ≤ ±5 mm). Any drift > 10 cm requires removal and re-laying.
- Q: What is the material aging cycle?
- A: Outdoor storage requires UV protection. In submerged service with quality fabric, service life can reach 15+ years (estimated). Avoid prolonged direct UV exposure.
6. Conclusion & Engineering Recommendations
By integrating material strength, construction precision and structural compaction, geotextile tubes coastal protection provide an efficient and cost-effective solution for marine defence—particularly suitable for soft foundations and heavily eroded zones.
Selection recommendations
For regions with currents > 1.5 m/s select tubes with longitudinal tensile strength ≥ 20 kN/m. For reclamation prioritize diameters of 3–5 m and match sand dry unit weight ≥ 14.5 kN/m³.
Construction recommendations
Maintain filling rates strictly at 20–30 m³/h. Underwater works must include divers for real-time probing to avoid blind filling.
Warranty & quality control
Require suppliers to provide material anti-aging test reports. Reserve a 12-month post-construction settlement monitoring period and ensure warranty coverage includes seam sealing and structural stability.
