Road Tunnel Safety Norms After Silkyara Incident

Why in News ?

Following the Silkyara Bend–Barkot Tunnel collapse on NH-134 (Char Dham Mahamarg Pariyojana) in Uttarakhand on 12 November 2023, the Ministry of Road Transport and Highways (MoRTH) has issued comprehensive tunnel safety guidelines.
The collapse trapped 41 workers for 17 days, exposing serious gaps in geological assessment, tunnel design, and emergency preparedness, especially in the fragile Himalayan region.

Background & Context

India’s recent infrastructure push—particularly under Char Dham Connectivity, strategic border roads, and mountain highways—has significantly increased tunnelling activity in geologically young and unstable terrains.

The Himalayas, being a fold mountain system, are prone to:

• Faults and fractures
• High seismicity
• Weak rock mass
• Water ingress and landslides

The Silkyara incident became a watershed moment, highlighting how procedural compliance-driven project execution failed to address ground realities, necessitating a risk-based engineering approach.

Why Tunnel Safety Matters

• Tunnels are critical for all-weather connectivity in:
  • Mountainous regions
  • Snow-bound areas
  • Congested urban zones
  • Strategic and border areas
• India’s expanding highway and strategic road network has amplified geological, human, and disaster risks.
• Tunnel failures can lead to:
  • Loss of life
  • Strategic disruptions
  • Cost overruns and public distrust

MoRTH Tunnel Safety Guidelines: Key Provisions

1. Strengthening Planning & Risk Assessment (DPR, GBR, Risk Register)

Issues Identified

• Detailed Project Reports (DPRs) treated as procedural formalities
• Inadequate geological and geotechnical investigations

Guidelines

• Project authority to verify accuracy and adequacy of geological investigations
• Mandatory preparation of:
  • Geotechnical Baseline Report (GBR)
  • Risk Register (hazards, risks, mitigation measures)
• Adoption of risk allocation principle: “Risk shall be borne by the party best equipped to manage it.”
• GBR and risk register to be shared with bidders to ensure transparency and realistic costing

2. Geological Realities & Design Challenges

Core Concerns

• Tunnel design depends heavily on the ground acting as a support system
• Predicting ground behaviour from limited tests is unreliable, especially in the Himalayas
• Poor geological investigation leads to:
  • Time overruns
  • Cost escalation
  • Structural failures

Special Conditions to be Assessed

• Squeezing and swelling ground
• Rock bursts
• Shallow overburden zones
• Tunnels below perennial streams/nalas
• Hot water ingress
• Toxic or flammable gases (especially in long tunnels)

3. Tunnelling Technologies: NATM vs TBM

New Austrian Tunnelling Method (NATM)

• “Design-as-you-go” approach
• Suitable for non-uniform rock conditions
• Controlled blasting
• Mandatory excavation and support sheet after each round

Tunnel Boring Machine (TBM)

• Suitable for uniform geological stretches
• Requires high vigilance against:
  • Roof collapse
  • Sudden water ingress

4. Collapse Risk Zoning & Safety Infrastructure

• Mandatory classification of tunnels into collapse-risk zones
• High-risk zones must include:
  • Np-4 escape pipe (minimum 0.9 m diameter)
  • Mobile rescue containers
  • Fixed rescue containers
  • Minimum 24-hour survival capacity for trapped workers

5. Emergency Response & Human Capacity

• Shift managers to be trained as first responders
• Mandatory Emergency Response Plan (ERP):
  • Prepared in advance
  • Updated weekly based on evolving site conditions
• Emphasis on human preparedness alongside engineering solutions

India’s Tunnel Infrastructure Snapshot

As per MoRTH’s reply in Parliament (December 12, 2024):

• 42 tunnels (60.37 km) completed under 27 NH projects
• 57 tunnels (93.96 km) under implementation in 37 NH projects
• 3 tunnels (9.68 km) approved at a cost of ₹1,962 crore
• One 6-lane PPP project in Maharashtra costing ₹4,501 crore, including 2 tunnels (3.47 km), cleared by the PPP Appraisal Committee

Challenges & Way Forward

Key Challenges

• Weak and non-scientific DPR preparation
• Complex Himalayan geology
• Inadequate on-site emergency preparedness
• Coordination gaps during rescue operations

Way Forward

• Institutionalise scientific, data-driven DPRs
• Integrate real-time geological monitoring
• Conduct periodic independent safety audits
• Clear role definition among:
  • Incident Commander (District Magistrate)
  • Construction agencies
  • Local administration
  • NDRF / SDRF commanders
• Armed Forces to ensure:
  • Technical support
  • Inter-agency coordination
  • Responder safety
  • Use these guidelines as a template for other sectors:
  • Metro rail
  • Hydropower projects