Gabion cage (i.e., wire mesh cage) construction must adhere to strict specifications and standards to ensure project quality, safety, and durability. The following are key construction specification requirements:
Material Requirements
Mesh Material:
Material: Typically uses hot-dip galvanized steel wire, Galfan (zinc-5% aluminum-mixed rare earth alloy) steel wire, or PVC/PE coated steel wire.
Coating Requirements: The coating amount must meet design requirements (e.g., hot-dip galvanized ≥245g/m²; Galfan ≥200g/m²). The PVC coating thickness must be uniform, firmly adhered, and the color is usually gray or green.
Mesh Size: As per design requirements (commonly 60×80mm, 80×100mm, 100×120mm, etc.). Allowable deviation ±4%.
Wire Diameter: Mesh wire ≥ 2.0-2.7mm, edge wire ≥ 2.7-3.4mm, binding wire ≥ 2.0-2.2mm (all before coating).
Mechanical Properties: Tensile strength ≥ 350-550MPa, elongation ≥ 10% (or as designed).
Filling Stone:
Material: Hard and durable, not easily weathered, not easily hydrolyzed (e.g., granite, limestone, etc.). Shale, mudstone, and severely weathered stones are prohibited.
Particle Size: Generally 1.5-2 times the mesh size (common particle size 80-250mm). Reasonable particle size distribution, porosity ≤ 30%, ensuring density and structural stability.
Density: ≥ 2.5 g/cm³ (or as designed).
Geotextile (Filter Layer):
When placed on fine-grained soil or requiring reverse filtration, a permeable geotextile (non-woven fabric) must be laid at the bottom and back.
Specifications must meet reverse filtration and strength requirements (e.g., unit area mass ≥ 250g/m², CBR puncture strength ≥ 2.5kN).
Foundation Treatment
Substrate Leveling: Remove vegetation, tree roots, silt, humus, etc. The foundation must be leveled and compacted, with a slope conforming to the design.
Foundation Bearing Capacity: Meets design requirements. Soft foundations require replacement, compaction, or reinforcement.
Drainage Facilities: Install drainage ditches, blind drains, etc., as required to prevent water accumulation and erosion of the foundation.
Laying the Filter Layer: Lay the geotextile as needed (overlap width ≥ 300mm) and anchor it appropriately.
Assembly and Installation
Unpacking and Assembly:
Unroll the wire mesh on a flat surface, and erect the side panels, end panels, and partitions along the folds.
Use dedicated binding wire (double strand) or fasteners to tightly bind the edges of adjacent panels and partition joints using a spiral or hinged method, with a spacing ≤100~150mm, and at least two turns at each point.
Ensure all folds, corners, and connection points are secure.
Positioning:
Place the assembled empty gabion cages accurately in the designed position, close to adjacent cages.
Positioning stakes or guy lines can be used to control the position and alignment.
Bottom Layer Stability: The bottom gabion is the foundation; its position must be precise, and its bottom must be flush with the base surface.
Gabion Box Connection:
The side panels and end panels of adjacent gabion boxes must be securely connected with binding wire to form a continuous structure.
The upper and lower layers of gabions should be stacked alternately (similar to bricklaying), and the top edge of the bottom layer should be securely connected to the bottom edge of the upper layer with binding wire.
Filling with Stones
Layered Filling: Each filling height should be ≤300mm (approximately 1/3 of the cage height). Avoid unilateral tilting that could cause panel deformation.
Manual Placement: Large stones should be manually placed on the outer layers and corners to ensure aesthetics and compactness; smaller stones should be used to fill internal gaps.
Compactness: Use appropriate tools to compact the stones, ensuring a filling rate ≥95%. After filling, the top surface of the stones should be slightly higher than the top of the cage (to allow for settlement).
Sealing:
After filling and leveling the top surface, fold down the cover plate to cover the gabion.
Tightly bind the edges of the cover plate to the upper edge of the cage and between adjacent cover plates with binding wire, with a spacing ≤100~150mm.
Quality Control Key Points
Geometric Dimensions: Length, width, and height deviation of the cage ≤ ±5%; verticality deviation ≤ 1.5%.
Binding Quality: All connection points must be secure, and the spacing between binding points must be uniform. Steel wire must be free of rust and damage, and broken ends must be pressed into the cage.
Filling Quality: Stones must be the correct size, neatly arranged, with a dense structure free of voids, and no inferior stones.
Flatness and Misalignment: Height difference between the tops of cages in the same layer ≤ 30mm; misalignment between adjacent cages ≤ 50mm.
Ecological Aspects: If ecological greening is required, cover the surface with soil or sow native plant seeds after filling.
Safety and Environmental Protection
Labor Protection: Construction workers must wear gloves and safety shoes, and take precautions to avoid injury when handling stones.
Foundation Pit Safety: Deep foundation pit operations require slope protection or shoring, and safety warnings must be posted.
Material Stacking: Stones and wire mesh cages must be stacked securely to prevent rolling.
Ecological Protection: Minimize surface disturbance; clean the site after completion and restore vegetation promptly.
Acceptance Standards
Key Control Items:
Complete material quality certification documents (certificates of conformity, test reports).
Foundation bearing capacity meets requirements.
Firm and complete binding connections.
Fitness, particle size, and density of filling stones meet standards.
Structural position (elevation, axis) deviations are acceptable.
General Items:
Cage appearance is flat; misalignment and settlement are within allowable ranges.
Geotextile laying meets requirements.
Site is clean.
Standards (Reference)
GB/T 343-2013 General Purpose Low Carbon Steel Wire
GB/T 25854-2010 Gabion Mesh
SL/T 779-2019 Technical Specification for Application of Gabion Mesh in Water Conservancy and Hydropower Projects
JTG/T D33-2012 Highway Drainage Design Specification (Involving Protection)
Design Drawings and Contract Technical Terms
