Case Study on Surface and Subsurface Water Ingress of Barog Tunnel in the State of Himachal Pradesh

Abstract

Introduction

Background:

• A 936-meter tunnel was constructed by NHAI between Kalka and Shimla (NH-05) from 2017 to 2019.

• The tunnel has enabled smooth traffic flow since 2019.

• In 2025, heavy rainfall has led to water-related structural issues, prompting an inspection and remedial plan.

I. Observed Problems:

1. Seepage at Construction Joints

   • Water leakage observed at several gantries (23, 24, 25, 26, 27, 52, 58, 59) causing dampness, leaching, and potential waterproof membrane failure.

2. Leakage from PQC and Pedestal Joints

   • Subsurface water (~5 L/min) observed from groove cutting areas, damaging PQC surfaces and affecting usability.

3. Cracks in Tunnel Lining

   • Both hairline and major cracks present, causing water seepage and risking structural integrity.

4. Choked Drains

   • Blockages at multiple locations leading to uncontrolled water flow inside the tunnel.

5. Damaged Drain Cleaning Pipe

   • Pipe at gantry 29 damaged, causing 4–5 L/min water flow.

6. Poor Housekeeping

   • Presence of dust and foreign materials, worsened by uncontrolled water flow, indicating inadequate maintenance.

II. Recommended Treatments:

III. Technical Overview of Water Management Methods:

A. Drainage Systems:

1. Blind Drain Pipes: Installed behind lining to collect water.

2. External Drains: Used in high water-table/karst regions to divert flow.

3. Relief Holes: Reduce pressure by allowing controlled drainage through rock mass.

B. Waterproofing & Grouting:

• Cement Grout: Inexpensive but less impermeable.

• Polymer Cement & Chemical Grout: More durable, waterproof, but costlier.

• HDPE/PVC Membranes: Prevent water ingress at the lining.

• Surface Sealants & Plugging: Used for microcracks and major weak zones.

C. Key Practices:

• Combine drainage with sealing techniques.

• Prevent water ingress during construction phase via design and geological study.

• Ensure continuous monitoring and maintenance of the drainage system.

Conclusion

Tunnel leakage is a persistent issue requiring multi-pronged solutions: Sealing (grouting/membranes) and efficient drainage are the foundation. Proper material selection, design detailing, and routine monitoring are essential. Water ingress causes range from: Geological factors (e.g., groundwater levels) Design flaws Construction errors Environmental exposure (e.g., excessive rain) Main solution: Grouting remains the most effective mitigation measure, though further research is needed into advanced materials and methods for long-term durability.

Copyright

Copyright © 2025 Deepak Parkash Gupta. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.