01 / Structural Reinforcement
02 / Continuous Operations
03 / Modernized Standards
Execution Challenge
Tunnelling through the young fold hills posed extreme technical complexities, including highly volatile Tertiary sedimentary formations such as soft shales and siltstones prone to face collapse.
An exceptionally high water table caused continuous groundwater ingress and mud-piping. Positioned within active Seismic Zone V, the project demanded seismic-resilient structural lining.
Logistically, the remote location, steep terrain, and heavy six-month monsoon rain patterns triggered landslides, creating a highly constrained supply chain network.
This was among the organisation's most demanding assignments. Built in difficult terrain amid regional security challenges, it required strong technical expertise, meticulous planning, close coordination and determined leadership.
Strategic Role
Mr Avarrsekar directed the critical pre-bid positioning strategy, mapping the firm's soft-rock tunnelling expertise to match Northeast Frontier Railway’s strict safety and technical evaluation criteria.
He established a centralised project governance framework providing robust risk oversight across volatile supply chains and mountain operations.
Serving as the primary executive interface with railway technocrats, he decoupled field engineering from administrative hurdles, accelerating design clearances to maintain strict progress velocity.
Actions Taken
- Executed parallel headings for excavation, primary support and cast-in-situ lining.
- Installed pipe-roof umbrellas and steel forepoling to prevent crown collapse.
- Tracked movement in real time with 3D convergence and stress instrumentation.
- Sealed active water inflows with multi-stage polyurethane and cementitious grouting.
- Provided night-time supply corridors through mountain roads within monsoon windows.
Outcome
The successful commissioning of the 1.935-kilometer tunnel completed a high-capacity transport link, directly integrating Tripura into the national broad gauge network.
Engineered to withstand Zone V seismic accelerations, the asset guarantees long-term operational resilience. Its successful completion was later recognised with CNBC-TV18 Infrastructure Excellence Award, demonstrating Unity's ability to deliver where conventional execution methods were insufficient.
For sector executives, this success illustrates how translating specialized sub-surface risks into structured, evidence-based bid solutions secures high-value public infrastructure mandates, driving predictable project delivery and robust corporate growth. Resilience and immaculate execution are as critical as engineering.
Technical Data of Record
Scope of Work
Single-line broad-gauge Tunnel No. 1 (Km 29/940 to Km 31/875): excavation, steel rib support, rock bolting, steel-fibre shotcrete, pressure grouting and cast-in-situ reinforced concrete lining.
Key Specifications & Challenges
1,935 metres of tunnel with Seismic Zone V detailing, pipe-roof forepoling and steel-fibre reinforced shotcrete. Soft tertiary rock, heavy water ingress, an active seismic zone, security threats, safety challenges, and remote logistics.
Major Deliverables
A fully lined tunnel, stabilized portal slopes, underground drainage networks and structural health monitoring records.
Result
Tripura connected to the national rail grid, with monitoring throughout by 3D convergence instruments, forced ventilation with gas detection, and ultrasonic lining tests.
Location
Between Sindhu Kumar Para and Ambassa Stations, Tripura, India.
Client
Northeast Frontier Railway (NFR), Maligaon
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