Skip to content

TECHNOLOGY

Seamless Co-Injection Reinforcement

UCG (Unsealed Combi Grouting) simultaneous injection method, which installs structural steel pipes
at regular intervals in soft ground such as weathering zones before tunnel excavation,
water sections at the top of low topsoil, and fault fracture zones, and injects injected materials to obtain ground reinforcement
and secondary effects Measures in the Korea Railroad Facilities Corporation’s
“Improvement Plan for Steel Pipe Multiple Grouting Method Management” (2018. 01): The project under design shall reflect the improvements
and improvements in the construction specifications,
but if necessary, review the improved construction method such as UCG co-injection method and implement technical review.

UCG Construction Sequence and Schematic Drawings

  • Step 1: Perforate
  • Step 2: Insert the steel pipe
  • - Perforation diameter:

    Φ 124m/m, perforation hole: 12.0m or more

  • - Stiffener specifications:

    • - Small diameter: Φ 60.5 m/m, T=4.0 m/m
    • - Large Diameter: Φ114.3m/m, T=6.0m/m
  • - Inlet tube sizes:

    Outer diameter Φ 12.7 m/m, inner diameter Φ 9.9 m/m

  • Step 3: Caulking
  • - Use caulking pack between UCG co-injection steel pipe outer wall and borehole inner wall (0.3M caulk at borehole entrance)

  • - Caulking:

    Foamed urethane

  • - Caulk must have a maximum pressure of 40 kg/cm2 or higher

Compare methods

Type UCG Co-Injection Method Conventional steel pipe reinforcement methods
Method Features
  • - Multiple inflation packers and injection tubes inside the steel pipe to create a quadranted space
  • - Simultaneous grout injection without sealing
  • - Factory-made co-injection pipes and caulking units ensure quality control
  • - Curing by inserting seal material between the drilled hole and the outside of the steel pipe
  • - Seal re-curing time is 18-24 hours (Railroad Administration guidelines)
  • - Install the packer inside the steel pipe and fill in steps 3 and 4
Schematic
Strengths
  • - No sealing application time and curing time required
  • - Air reduction with co-injection steel pipe
  • - Environmentally friendly, mineral-based injectables
  • - 2Mpa strength after 4 hours
  • - Visual monitoring of infusion pressure, infusion volume
  • - The price per space is low
  • - Lots of examples
  • - Easy to make steel pipes
Weaknesses
  • - Concurrent steel pipe fabrication slightly increases material costs
  • - Sealing requires 18 to 24 hours of curing time
  • - This infusion is 4 infusions per ball to increase the air volume
  • - Constructability degradation to 3.2 day/span
  • - Water glass reduces strength and pollutes the environment
  • Step 4: Simultaneous injection
  • - The injection material is a combination of cement grout and mineralized quick setting ash.
  • - Injection pressure is determined by site conditions and geologic conditions.
  • - Apply P = 10 to 15 kg/㎠ (ΔP=1 to 10 kg/㎠)
  • Step 3: Caulking

Method Attributes

×