Do It Yourself Gabion Retaining Walls for Rural Roads

History of Gabions (MORD 27, Clause 1.0)

• Origin: Gabion (Italian gabbione = "big cage") dates back 2000+ years, first used by Egyptians with willow baskets filled with stones to prevent Nile bank erosion.
• Types: Cylindrical willow baskets, metal cages, or boxes filled with stones, concrete, sand, or soil.
• Applications:
  • Erosion control (shorelines, stream banks, slopes)
  • Retaining walls (battered or stepped back)
  • Military protection (earth/sand-filled)
  • Floodwalls, dams, river training, channel lining
• Advantages:
  • Modular, stackable, resistant to washout
  • Flexible, energy dissipating, free-draining
  • Strength increases over time with silt and vegetation
  • Prevents rockfalls on roads

Key Specifications for Machine-made Gabions (Clause 3.1 & 4.1)

• Material: Hexagonal double-twisted steel wire mesh, zinc or zinc+PVC coated.
• Structure: Divided by diaphragms (~1m spacing) for stability.
• Void Ratio: ~30% for free drainage.
• Standard Sizes (10x12 mesh type):

Summary Diagram: Gabion Structure

graph TD
  A[Gabion Box] --> B[Wire Mesh (Hexagonal, Double Twisted)]
  B --> C[Zinc or Zinc+PVC Coating]
  A --> D[Filled with Stones/Concrete/Soil]

Machine Made Gabion: Key Specifications & Details (per MORD 27 & IS-16014)

Description:

• Rectangular baskets of double twisted hexagonal steel wire mesh.
• Divided into cells by diaphragms at ~1 m centers.
• Wire coated with zinc or zinc + PVC for corrosion resistance.
• Edges are selvedged with thicker wire for reinforcement.
• Filled onsite with hard, durable rock.
• Offers 30-40% voids for free drainage and slope stability.

Key Features:

• Double twisted wire mesh prevents unraveling when cut.
• Hexagonal mesh ensures uniform force distribution.
• Modular, easy to assemble, no specialized labor needed.
• Can be used for toe walls, breast walls, and slope protection.
• Provides flexible, permeable, monolithic structure.

Typical Dimensions & Parameters:

Summary Diagram:

graph TD
    A[Gabion Box] --> B[Hexagonal Double Twisted Wire Mesh]
    B --> C[Diaphragms at 1m spacing]
    A --> D[Selvedged Edges with thicker wire]
    A --> E[Filled with durable rock]
    A --> F[30-40% voids for drainage]
    F --> G[Ensures slope stability]

References:

• IS 16014 (Wire Mesh Gabions)
• MORTH Section 2500 (Road Works Specifications)

Comparative Summary: Handmade vs. Machine Made Gabions (IS Code MORD 27, Clause 3.0)

Key Notes:

• Selvedging in machine made gabions enhances rigidity and prevents mesh deformation.
• Double twist hexagonal mesh in machine made gabions distributes loads uniformly and limits damage propagation.
• Handmade gabions are prone to rust and instability due to variable mesh quality and lack of standardization.

flowchart LR
    A[Handmade Gabion] --> B[Non-uniform mesh]
    A --> C[No selvedging]
    A --> D[Commercial coating]
    B --> E[Mesh enlargement & fill escape]
    C --> F[Lower structural strength]
    D --> G[Prone to rust in 3-4 months]

    H[Machine Made Gabion] --> I[Uniform hexagonal mesh]
    H --> J[Selvedged edges]
    H --> K[Standard zinc coating]
    I --> L[Prevents bulging & fill escape]
    J

Technical Parameters of Gabion Mesh (10x12 Zn + PVC Coated)

Typical Standard Sizes of Gabion Box (10x12 Mesh type)

Notes:

• ID = Inner Diameter, OD = Outer Diameter of wire.
• Zinc coating ensures corrosion resistance; higher gm/sqm for larger diameters.
• Diaphragms provide internal support to maintain shape and improve stability.

graph LR
A[Gabion Mesh] --> B(Mesh Wire Diameter 2.7/3.7 mm)
A --> C(Edge Wire Diameter 3.4/4.4 mm)
A --> D(Lacing Wire Diameter 2.2/3.2 mm)
A --> E(PVC Coating 0.5 mm

Key Features & Characteristics of Gabions (MORD 27 - Clause 5.0):

• Material: Machine-made gabions use galvanized or PVC-coated wire mesh for durability and corrosion resistance.
• Dimensions: Standard gabion baskets are typically 1m x 1m x 1m or customized as per site requirements.
• Strength: Wire mesh tensile strength generally ranges from 380 to 550 N/mm².
• Permeability: Gabions allow free drainage, reducing hydrostatic pressure behind retaining structures.
• Flexibility: Gabions can deform without losing structural integrity, adapting to ground movements.
• Durability: Expected service life exceeds 50 years with proper coating.
• Filling: Filled with hard, angular stones of size 40-150 mm, ensuring interlocking and stability.
• Installation: Easy to install with minimal skilled labor; no curing time unlike concrete.

Typical Technical Parameters Summary

flowchart LR
    A[Gabion Basket] --> B[Wire Mesh]
    A --> C[Stone Filling]
    B --> D[Galvanized or PVC Coated]
    C --> E[Angular Stones 40-150 mm]
    A --> F[Flexible & Permeable Structure]
    F --> G[Adapts to Ground Movement]
    F --> H[Allows Drainage]

This concise overview aligns with MORD 27 Clause 5, providing essential specs and characteristics for gabion design and application.

Gabion Installation Procedure (MORD 27 - Clause 6.0)

1. Gabion Preparation:

   • Open and unfold gabions to original box shape.
   • Lift front, back, end panels vertically.
   • Lift inner diaphragms vertically and secure by lacing wire.
   • Tie all diaphragm and end panel edges to front and back panels.

2. Lacing Operation:

   • Cut sufficient wire length.
   • Secure lacing wire with alternate double and single loops per mesh opening.
   • Double loops at intervals ≤ 150 mm.

3. Foundation Preparation:

   • Level the foundation surface.
   • Install geotextile if required for subsurface drainage.

4. Gabion Placement & Filling:

   • Place pre-assembled empty gabions in position.
   • Tie adjacent gabions along all edges to form a monolithic unit.
   • Place gabions front-to-front and back-to-back.
   • Use stones sized 150 mm to 250 mm.
   • Fill in lifts:
     • 300 mm for 1 m high gabions,
     • 250 mm for 0.5 m high gabions.
   • Fill layer max 300 mm higher than adjoining cells.
   • Hand compact rocks to minimize voids.
   • Hand place rocks on exposed faces to reduce voids.

5. Cross Ties:

   • Install internal cross ties at vertical third points for 1 m high gabions.
   • For gabions with two exposed sides, install cross ties perpendicular to lateral exposed face.

Typical Standard Sizes of Gabion Box (10x12 Mesh) - Clause 4.1

Typical Applications for Rural Roads (MORD 27, Clause 7)

Key Applications:

• Gabion Structures: Used extensively for retaining walls, crash barriers, slope stabilization, and bank protection.
• Crash Barriers: Gabions on sharp curves in hilly terrain improve safety (Fig. 22, 23).
• Slope Stabilization: Retaining walls prevent road failures on valley and hillside slopes (Fig. 24a&b).
• Gabion Gravity Retaining Walls:
  • Base width = 0.5 to 0.7 × Wall height (H)
  • Suitable for walls up to 6 m high
  • Use local stones, labor-intensive but cost-effective (Fig. 25a&b).
• Mechanically Stabilized Earth (MSE) Walls:
  • Gabion facia + double twist mesh reinforcement
  • Can be stepped or vertical face (Fig. 28, 29)
  • Economical, use local granular backfill.
• Green Facia Soil Reinforcement:
  • Gabion mesh with coir mat for vegetation growth
  • Enhances slope stability and aesthetics (Fig. 30, 31).

Bank Protection:

• Gabion Mattress: For riverbank and pavement protection (Fig. 19, 20).

Summary Table: Gabion Gravity Wall Design

flowchart TD
    A[Rural Road] --> B[Gabion Retaining Wall]
    A --> C[Gabion Crash Barrier on Sharp Curves]
    A --> D[Gabion Mattress for Bank Protection]
    B --> E[Gravity Wall (Base = 0.5-0.7 H)]
    B --> F[MSE Wall with Double Twist Mesh]
    F --> G[Green Facia with Coir Mat]

This approach balances cost, local materials, and environmental considerations for rural road stabilization and safety.

Typical Sections of Gabion Wall (IS Code MORD 27)

Key Specifications:

• Gabion Boxes: Machine-made, 10x12 mesh type.
• Standard Sizes (Clause 4.1):

Design Notes:

• Diaphragms provide internal bracing to maintain shape and improve stability.
• Typical width is 1 m; height varies between 0.5 m to 1 m.
• Gabion walls are often constructed in stepped or battered sections for stability.
• Non-woven geotextiles are recommended behind gabion walls for filtration and separation.

Typical Section Illustration:

graph TD
    A[Top View]
    B[Side View]
    C[Gabion Box (Length x Width x Height)]
    D[Diaphragms inside box]
    E[Backfill soil]
    F[Non-woven Geotextile]

    A --> C
    C --> D
    B --> C
    B --> E
    E --> F

Use these standard sizes and diaphragm counts for modular design and installation of gabion retaining walls per MORD 27.

Comparative Summary: Gabion vs. PCC/RCC/RR Masonry Walls (IS Code MORD 27, Clause 9.0)

Key Notes:

• Gabion walls are preferred where flexibility, drainage, environmental friendliness, and ease of construction are priorities.
• PCC/RCC/RR walls are suitable for rigid, high-load applications but require careful foundation and drainage design.

Visual Concept: Flexibility & Drainage

graph LR
A[Gabion Wall] --> B[Flexible Structure]
A --> C[Permeable - Allows Drainage]
D[PCC/RCC/RR Wall] --> E[Rigid Structure]
D --> F[Impermeable - Requires Drainage System]

For detailed design, refer to IS codes on retaining walls and gabion specifications.