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Pre- and post-excavation groutingWater cut off and weak ground consolidated ahead of the face; voids closed behind it.Cavity and void fillingVoids above tunnel crowns, behind linings and under slabs filled without loading the support.Tunnel rehabilitationOld and operating tunnels: seepage stopped, ground consolidated and lining repaired, under traffic.

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Track and slab re-levellingSettled ballastless track and slabs lifted back to level by PU injection, on live lines.Permeation and chemical groutingWeak, loose or wet ground strengthened and sealed by resins and gels that fill it without moving it.TAM groutingStaged grouting through sleeve pipes for shafts, foundations and deep excavations.Curtain and consolidation groutingSeepage cut-offs and foundation consolidation for dams, barrages, shafts and structures.Ground investigation and monitoringERT, GPR and MASW surveys, boreholes, lab tests and instruments, before and after treatment.

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Rock bolting and self-drilling anchorsRock bolts, self-drilling and prestressed anchors for tunnels, portals, slopes and caverns.Slope stabilisationSoil nails, anchors, mesh, drainage and rockfall barriers for slopes above roads, railways and towns.Mine shaft and strata treatmentWater sealed in shafts and declines; weak roof and face strata consolidated with resins and bolts.
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Railways · Tunnels

Tunnel T-77D, USBRL, Banihal

In T-77D near Banihal, a collapse at the crown left a longitudinal cavity of about 8 to 10 m in highly fractured, water-bearing rock under high overburden, below a nallah. The ground surface above began to settle. We filled the cavity and grouted the ground around it so the work could continue safely.

Location
Banihal, Jammu & Kashmir
Type
Railway tunnel
Client
IRCON International Limited

Project recordExecuted by GCPL for IRCON, as confirmed by the company in October 2026.

The problem

A collapse at the crown

  • Highly fractured rock with saturated soil.
  • Thrusts and faults along the alignment.
  • High overburden pressure.
  • A nallah over the tunnel.

Challenges

What made it hard

  • A cavity of about 8 to 10 m along the crown.
  • Weathered rock in the excavation zone.
  • Loss of ground water threatening further collapse.
  • Settlement at the surface above the tunnel, a concern for the community living there.

What we did

Fill the cavity, consolidate the ground, control the water

  • Cavity filling and reinforcement of the ground around the crown.
  • Grouting under high pressure.
  • Water ingress control.
Filling a cavity above a tunnel crownCross section of a tunnel under steel ribs and shotcrete with a void above the crown left by a collapse. Pipes drilled through the support carry high-foaming PU into the void, which fills from the bottom up and binds the loose material. VOID STILL OPEN1234567
  1. A void above the crown, left by a collapse or by overbreak.
  2. Loose material that keeps running if it is disturbed.
  3. Steel ribs and shotcrete holding the opening.
  4. Pipes or self-drilling anchors drilled through the support into the void.
  5. High-foaming PU fills the void from the bottom up and binds the loose material.
  6. Cured foam is light, so it adds little load to the support below it.
  7. Check holes and pressure readings confirm the void is full before the next advance.
Geo Constech
Cavity filling · Typical arrangement
Not a record of this site
Schematic · Not to scale

Services on this job

Methods used

Cavity and void filling

Voids above tunnel crowns, behind linings and under slabs filled without loading the support.

Tunnel water ingress control

Leaks and inflow stopped in tunnels, shafts and underground structures.

Project recordExecuted by GCPL for IRCON, as confirmed by the company in October 2026.

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