Wave-resistant tubular bags for beaches

Wave-resistant geotextile tubes are typically made of high-tenacity polypropylene and are generally black in color; the material weight is commonly 400 g/m², adjusted according to product specifications. While length is unlimited and width can be extended via multi-panel splicing, the required material strength depends directly on the width—the wider the tube, the higher the required strength. The filling height is generally set at two-thirds of the tube's diameter. Customization is available based on the diameter of the site's grouting equipment, and chemical additives can be incorporated as needed to accelerate solidification and the separation of solids from water.

Comparison of wave-resistant geotextile tube dredging with other dredging methods:

1.  **Traditional natural dewatering in sediment disposal areas:** This method for treating river and reservoir sediment involves simple technology but requires a large land footprint; it is a common approach for sediment treatment projects in China (including sediment cleanup in Taihu Lake). However, this dewatering method is highly inefficient, and the practice of stockpiling contaminated sediment poses certain environmental and safety risks. Because the sediment in the disposal area remains exposed and in direct contact with the surrounding environment, failure to properly treat residual water can lead to secondary pollution of nearby water bodies.

2.  **Mechanical dewatering methods:** Used for treating sediment contaminated with organic matter and heavy metals, these methods offer good dewatering results but suffer from drawbacks such as high initial equipment investment, energy consumption, the need for dedicated processing facilities, and processing capacities that often fail to meet the tight schedules required for on-site river and reservoir sediment remediation.

3.  **Geotextile tube dredging:** **Convenience:** Tube diameters and lengths can be adjusted as needed; they are highly adaptable, stackable, and easy to transport. **Environmental friendliness:** Operations are fully enclosed, generating minimal noise and posing little risk of secondary pollution. **High efficiency:** Capable of handling required wastewater and sludge volumes; the number of tubes used can be scaled up or down based on pump flow rates. **Effective volume reduction:** Sludge volume can be reduced by over 90% within one month, simplifying subsequent removal and disposal. **Broad applicability:** Suitable for wastewater treatment and sludge dewatering projects of all sizes. Construction method for wave-resistant geotextile tubes:

Step 1: Filling. High-strength, permeable geotextile is fabricated into the required tube shape, which is then filled with slurry.

Step 2: Dewatering. The geotextile material features fine pores that retain solid particles while allowing water to drain out, effectively reducing the volume of the contained material; the tube can be refilled repeatedly until the material reaches its maximum allowable height, and the discharged water can be recycled.

Step 3: Consolidation. Following repeated filling and dewatering cycles, the fine particles remaining inside the tube gradually consolidate as they dry.

Technical advantages of wave-resistant geotextile tubes:

(1) Tube volume is highly adjustable, allowing for flexible handling capacities;

(2) No investment in mechanical dewatering equipment, power supply, or relocation is required;

(3) Low investment cost, minimal labor requirements, and simple operation;

(4) Tubes can be placed at any suitable location along riverbanks or lakeshores, with clear effluent discharging directly back into the water body;

(5) Tubes can be positioned at multiple locations to match dredging vessel operations, making them ideal for in-situ sludge dewatering;

(6) The dewatering process is enclosed, preventing secondary pollution;

(7) Sludge moisture content can be adjusted by controlling filling frequency, pressure, and resting time;

(8) Uses specialized filter fabric offering excellent filtration performance, high strength, and resistance to aging;

(9) Reagent formulas can be adjusted based on sludge characteristics to ensure harmless treatment;

(10) Dewatered sludge can be used for river/lake bank protection, agriculture, or landscaping;

(11) Low system investment and operating costs, combined with a short construction period. Size Selection

Laying and Anchoring of Wave-Resistant Geotextile Tubes

The laying of wave-resistant geotextile tubes is scheduled for low-tide periods when the seabed is exposed; prior to installation, the area must be cleared of riprap, debris, and other objects that could compromise quality.

Once transported to the site, the prepared tubes are laid out according to the staked positions. To prevent rolling, sliding, or displacement during filling and to ensure accurate placement, the tubes must be anchored. For the bottom layer, anchoring is achieved by driving steel pipes into the seabed alongside the tube and connecting them via anchoring rings attached to the tube. Once the bottom layer is filled, the upper-layer tubes are anchored by tying their side pull-rings to the filled bottom tubes using geotextile straps, effectively binding them into a single unit.

Filling of Wave-Resistant Geotextile Tubes

High-tenacity polypropylene wave-resistant tubes are filled using a 22 kW jet-suction slurry pump unit mounted on a flat-deck barge. After underwater jet-suction dredging, the pump's discharge pipe is inserted into the filling sleeve of the laid-out tube to inject the sand-slurry mixture.

Filling begins at the sleeve located at one end of the tube, while water drains from the opposite end; this flow pattern facilitates sand sedimentation and improves efficiency. During the process, operators must frequently monitor sand accumulation at the discharge point, adjust the discharge pipe position and filling sleeve accordingly, and manually tread back and forth across the top of the tube. This treading action rearranges soil particles for greater density, ensures uniform and full sand distribution, guarantees a level surface, and accelerates drainage and consolidation. Once the tube reaches the "slurry-blocking" stage (indicating it is full), the filling rate is reduced or stopped to prevent the fabric from bursting, allowing time for consolidation and dewatering. During the filling process, survey personnel control the top elevation of each sandbag layer based on the cross-sectional drawings of the sandbag-core dike. If the desired height is not achieved in a single pass, filling is resumed—once or multiple times—after the sandbags have undergone some initial consolidation, continuing until the target degree of fullness is reached.