How is RCC used in tunnels?

Short Answer:

RCC (Reinforced Cement Concrete) is used in tunnels to provide strong, stable, and durable support against earth pressure, water ingress, and vibration. It forms the lining, roof, and sometimes even the base of tunnels, ensuring that the structure remains safe during and after construction.

In tunnel construction, RCC is used as cast-in-situ or precast lining segments. It helps resist deformation, withstands ground load, and improves tunnel life. Special waterproofing, reinforcement detailing, and high-strength concrete are used to ensure durability in underground conditions.

Detailed Explanation:

RCC used in tunnels

Tunnels are underground passages built for transportation, drainage, power cables, or utility purposes. RCC plays a critical role in tunnel construction because it offers both strength and durability needed to resist soil pressure, groundwater, and operational loads. The use of RCC ensures safety, serviceability, and long-term stability of the tunnel structure.

Tunnel linings made of RCC can be cast directly at the site (cast-in-situ) or pre-manufactured (precast) and installed inside the tunnel using machinery. Both methods help form a solid protective shell that resists collapse and environmental effects such as water leakage, soil movement, and chemical reactions.

How RCC Is Used in Tunnel Construction

  1. Tunnel Lining
    • The most common use of RCC in tunnels is for lining the inside surface.
    • RCC linings act as a permanent support system, providing resistance against soil movement and water seepage.
    • It forms a protective shield that allows safe movement of people, vehicles, or fluids through the tunnel.
  2. Roof and Wall Support
    • RCC is used in constructing tunnel roofs and side walls to hold back the surrounding soil and rock.
    • It handles both vertical and lateral loads effectively.
    • The reinforcement bars inside the concrete increase its tensile strength.
  3. Base Slab and Flooring
    • The tunnel floor or base slab is made of RCC to support the weight of vehicles, tracks, or pipelines.
    • It also prevents uplift due to groundwater pressure and provides a solid base for other structures.
  4. Segmental Tunnel Linings (Precast RCC)
    • In tunnel boring machine (TBM) projects, precast RCC segments are manufactured off-site.
    • These segments are assembled inside the tunnel as the boring progresses.
    • They are fast to install and provide high accuracy and quality.
  5. Shotcrete and In-situ Concrete
    • Shotcrete (sprayed concrete) with reinforcement is used for initial lining and support.
    • Final RCC linings are then cast in-situ for smooth finishes and added strength.
  6. Waterproofing with RCC
    • Waterproof membranes are placed behind RCC linings.
    • RCC resists moisture and protects internal tunnel components from water ingress.
  7. Integration with Tunnel Systems
    • RCC linings are embedded with ducts, lighting supports, and service channels.
    • Openings and inserts are cast into the RCC structure to accommodate cables, pipes, and ventilation.

Advantages of RCC in Tunnel Construction

  • High Strength to resist soil and live loads.
  • Durability against moisture, chemicals, and mechanical wear.
  • Versatility to mold into curved or complex tunnel shapes.
  • Fire Resistance provides safety during emergencies.
  • Low Maintenance for long-term tunnel service life.
Conclusion:

RCC is essential in tunnel construction for providing strength, support, waterproofing, and stability. It is used in linings, walls, roofs, and bases to ensure tunnel safety and longevity. By using proper reinforcement and construction techniques, RCC helps create strong tunnels that withstand environmental and load conditions for many years.