Rock bag / Net bag for bag-type foot protection

Bottle Unit

  • Naturnaher Wasserbau (Near-natural river engineering) product
  • Construction technology examination certificate report No. 0109
  • MLIT issued “Bag type bag material for foot protection performance regulation (long-term performance type)” compliant product
  • “Rubble Net Layered Construction Method” Design and Construction Manual Performance certificate qualified product (certificate No. 1506)
  • Conformity product of Disaster recovery basic policy to protect beautiful mountains and rivers
  • CE marking
New Technology Information System (NETIS) Registration Number: KT-000028-VE
Bottle Unit


Rock bag material for foot protection method, fitting landscape changes occurring in the river bottom and fits to unevenness and gaps.

The Bottle Unit/ROCK BAG(NET GABION) is a double-layer raschel net structure bag material made by polyester fibers. It can be used with filling materials such as boulders, gravels, rubbles and concrete lumps that can be sourced at site. The bag has the soft adequate shape to follow changes in the river bottom, which is required for the revetment foundation consolidation work, and also the ability to fit into gaps, which is required for space filling work.

According to the amounts of filling materials, selection can be made from four types of bags containing 1, 2, 3 and 4t. 

Filling bag procedure


  • During installation, the mouth closing part (knot part) does not protrude, so that when installed in rivers the bag shape will not easily become caught up by flotsam.
  • The bags have outstanding weather resistance, chemical resistance, resistance to cold and heat, and shock resistance.
  • Due to the double structure net and the 25mm mesh spacing, even if ruptures occur in a number of locations, the structure will prevent the filling materials from escaping.
  • Because mechanical installation is mainly used both in the filling work and in the placement work, it will be possible to shorten the construction period.
  • By using underwater lifting jigs, underwater installation will also be simple.

3t bag

Mouth closing part


  • Revetment, bridge pier foot protection work and river bed protection work
  • Temporary road foundation construction work
  • Space filling work for foot protection blocks
  • Revetment, bridge pier foot protection work and scouring prevention
  • Foot protection work in offshore wind farms

Standard / specification

Standards/product No.

Type For 1t 
For 2t
For 3t
For 4t
Specification Standard(W×H)(mm) 2500×1500 2800×2100 3400×2200 3400×2600
Shape Bag double ply
Netting FBU-10,FBU-20,FBU-30,FBU-40:
 Recycled Polyester Raschel net(Black spun-dyed)
 Polyester Raschel net(Black spun-dyed)
Composition 1670dtex※4 ×10 strands 1670dtex※4 ×15 strands
Mesh spacing(mm) 25
Mouth Closing rope Polyester (Black spun-dyed): ø 6mm

Lifting rope

(6 points anchoring)

Polyester (Black spun-dyed): ø 9mm Polyester (Black spun-dyed) :ø 12mm
Base Binding rope Polyester (Black spun-dyed) :ø 9mm
Strength characteristics Netting Tensile strength※2
 450N(Approx.45 kgf)/strands or more
Tensile strain:25% or more , and 40% or less
Tensile strength※2
 650N(Approx.65 kgf)/strands or more
Tensile strain:25% or more , and 40% or less
Mouth Closing rope

Polyester : ø 6mm
Tensile strength※3 3.5kN(Approx.0.35 tf) or more
Tensile strain:40% or more

Lifting rope

(6 points anchoring)

Polyester : ø 9mm
Tensile strength※3 12kN(Approx.1.2 tf) or more
Tensile strain:40% or less
Polyester : ø 12mm
Tensile strength※3 22kN(Approx.2.2 tf) or more
Tensile strain:40% or less
Base Binding rope Polyester : ø 9mm
Tensile strength※3 12kN(Approx.1.2 tf) or more
Tensile strain:40% or less
Usage Filling material Boulders, gravels, rubbles, concrete lumps
 (Sizes from 50mm up to human head size), etc.
Approximate capacity(m3) Approx.0.5 to 0.62 Approx.1 to 1.25 Approx.1.5 to 1.9 Approx.2 to 2.5
Mass(t) Approx. 1※6 Approx. 2※6 Approx. 3※6 Approx. 4※6
  • ※1: Black spun-dyed yarn: Kneading carbon black material into raw material, spin, extend and make the yarn.
    ※2: Tensile strength: conforming to JIS A 8960
    ※3: Tensile strength: conforming to JIS L 2707
    ※4:”dtex” is an unit shows the size of yarn by expressed by its mass in gram(g) per 10000m
    ※5: Bag material will be easier to break if using over-sized filling material
    ※6: Above showed number indicates the referential mass when filling standard sized stone (rubble of diameter 50 to human head-size) . If using broken concrete blocks as filling material, specific gravity is lighter and may not have the same mass rate.

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