Kollam: The National Highways Authority of India (NHAI) has attributed the collapse of a Reinforced Soil (RS) wall at Mylakkadu, part of the NH-66 development project in Kollam, to bearing capacity failure and poor soil quality. The agency has confirmed that corrective and punitive actions are being taken against the contractor and the engineering firm responsible for the project.

According to NHAI, a preliminary assessment indicates that the collapse, which occurred on December 5, was caused by a deep-seated shear or bearing capacity failure. This implies that the soil at the foundation of the wall was too weak to support the load of the fill material used in the RS wall, leading to structural failure. The wall, which stood 9.4 meters high, was constructed as an approach to a vehicular underpass on the Kollam-Kadambattukonam stretch of NH-66 and was under construction at the time of the collapse.

In response, NHAI has temporarily suspended the concessionaire, its promoters, and the independent engineering firm from bidding for future projects. Show-cause notices have been issued, and monetary penalties are under consideration as part of potential debarment proceedings. Additionally, the project manager of the concessionaire and the resident engineer overseeing the RS wall construction have been removed from the project site.

While NHAI acknowledged that RS wall technology is generally well-established, the recent collapse raises concerns about the soil quality and design considerations for such structures along NH-66. “The failures underline serious concerns regarding the bearing capacity and quality of the soil used in the design and construction of RS walls,” the agency said in a statement.

To address the issue and prevent recurrence, NHAI has initiated a comprehensive review of RS wall projects across Kerala. A high-level expert committee, including Jimmy Thomas and TK Sudheesh, visited the site on December 6 to examine the failure and recommend corrective measures. The agency is also implementing findings from a previous expert committee report following the Kooriyad NH collapse.

In a broader preventive measure, NHAI has appointed 18 geotechnical agencies to conduct soil sampling and testing at 378 RS wall and related structure sites across 18 NH-66 projects in Kerala. These tests will include projects that are already constructed, under construction, or yet to begin. Fieldwork is expected to commence within seven to ten days, with testing completed at 100 locations within a month and the remainder within three months.

Based on these investigations, every RS wall will undergo reassessment, incorporating field and laboratory reports to ensure structural integrity. Where necessary, remedial actions such as dismantling and reconstruction will be carried out. NHAI emphasized that no RS wall will be accepted until quality standards are verified and accountability is established for any lapses identified during the review process.

The Kollam RS wall collapse follows another incident in November on the Aroor-Thuravoor Elevated Road Project, where girders fell during construction. Following that event, NHAI had already engaged RITES to conduct a safety audit of the project. The agency has now decided to expand this audit to other NH-66 projects to proactively identify and address potential safety hazards.

NHAI officials highlighted that ensuring the stability and quality of RS walls is critical given the extensive use of such structures in the highway development projects across Kerala. The agency noted that RS walls provide an effective solution for stabilizing embankments and supporting road infrastructure, but their success depends on careful assessment of soil properties, design adequacy, and quality construction practices.

Experts have stressed that soil bearing capacity is fundamental in civil engineering, particularly for retaining structures. Inadequate foundation strength can lead to sudden failures, endangering lives and disrupting traffic. NHAI’s current measures, including large-scale soil testing and expert-led reviews, aim to prevent similar incidents in the future.

The agency also reiterated its commitment to transparency and accountability, stating that lapses discovered during the review would lead to appropriate penalties and corrective action. The process will involve strict monitoring of construction practices, validation of soil reports, and adherence to design specifications for all RS walls and related structures.

The NH-66 corridor in Kerala, which is undergoing extensive development to improve connectivity along the western coast, has seen multiple infrastructure projects involving elevated roads, bridges, and retaining walls. NHAI’s proactive approach is intended to strengthen safety protocols, ensure compliance with engineering standards, and restore public confidence in the ongoing highway projects.

As investigations continue, local authorities have been urged to cooperate with NHAI and assist in monitoring construction safety. The agency has also emphasized the need for ongoing training of engineers and contractors to prevent technical oversights and ensure high-quality construction practices.

In conclusion, NHAI’s statement underscores the dual responsibility of ensuring engineering reliability and enforcing accountability in highway construction. The Kollam RS wall collapse serves as a critical reminder of the importance of soil assessment, quality control, and rigorous monitoring in large-scale infrastructure projects. The ongoing investigations, combined with comprehensive safety audits and remedial actions, aim to mitigate future risks and reinforce the structural integrity of NH-66 developments across Kerala.