RS wall guidelines

NHAI Releases New Guidelines for RS Wall Construction | October 2025

Published on October 22, 2025, 06:35 AM IST

The National Highways Authority of India (NHAI) has issued a significant update to its construction guidelines with the release of the Policy Guidelines/Miscellaneous/2025, effective from October 21, 2025. This circular, numbered 18.11/2025 and decision file No. DESGN/23/2020-25 dated October 21, 2025 (Comp. No. 296551), focuses on discontinuing certain construction practices for Retaining Structure (RS) walls and introducing remedial measures to enhance highway safety and structural integrity.

Background and Purpose

The new guidelines were developed following extensive deliberations in capacity-building sessions held on May 17, 2025, June 12, 2025, and August 5, 2025. These sessions addressed recurring issues such as excessive settlement, structural failures, and safety concerns observed in RS wall constructions, particularly where gap slabs between abutments and RS walls have led to compromised stability.

Key Guidelines to Discontinue Construction Practices

NHAI has outlined specific practices to be discontinued to mitigate risks:

1. Gap Slabs Between Abutments and RS Walls: Construction of gap slabs between abutments and RS walls, especially where RS walls exceed 10 meters in height, should be discontinued due to observed failures.
2. RS Walls Over 10m Height: Construction of RS walls with earthwork layers exceeding 10 meters (w.r.t. NGL) should be avoided. For grade-separated structures like ROBs over 10 meters, the length of viaduct portions should be increased to meet the height limit.
3. Vertical Load Transfer: Avoid transferring the vertical load of the approach slab onto the RCC return wall. Instead, use a column-type abutment with a dirt wall or RCC bracket to support the approach slab independently.
4. RS Wall Approaches with Crash Barriers: For RS wall approaches, the crash barrier with a friction slab should be an independent unit, constructed with RCC and placed below the approach slab, PQC pavement, or road crust, avoiding monolithic connections.

Recommended Construction Practices

To replace discontinued practices, NHAI has introduced the following measures:

5. Construction Practices for Gap Slabs: Use column-type abutments with dirt walls or RCC brackets to support the approach slab independently, ensuring no overlapping support with the RCC return wall.
6. RS Walls with Partial Height/Surcharge: Avoid RS walls with partial height or surcharge. If required, use RCC retaining walls of full or partial height with surcharge provided independently.
7. RS Walls as Wing Walls: Provision of RS walls as wing walls for grade-separated structures or other structures should be avoided; only RCC wing walls should be used.
8. Geo-Composite Membrane: Install a geo-composite membrane as a drainage layer with a minimum width of 600mm at the back of RS walls, adhering to the gradation in Table-2 of IRC:SP:102.

Implementation for Ongoing Projects

For ongoing projects (bids received, awarded, or works under construction), the application of these remedial measures will be decided by the Technical Divisions with the approval of the member concerned. The guidelines were circulated on October 21, 2025, by Chief General Manager (Coord.) and are mandatory for all NHAI HQ/ROs/PIUs/CMUs/Site Offices.

Impact and Compliance

These updates aim to enhance the safety and longevity of highway infrastructure by addressing structural vulnerabilities. The circular will be translated into Hindi, hosted on the library site, and circulated widely to ensure compliance. Contractors and engineers are urged to align ongoing projects with these standards to avoid safety risks and penalties.

Reference Document: NHAI Policy Guidelines/Miscellaneous/2025 (Decision File No. 18.11/2025)