The recent collapse of the National Highway 66 (NH-66) embankment in Kerala has triggered a major debate and urgent calls for reform in engineering practices – construction quality and project oversight in India’s infrastructure sector.
What Happened on NH-66 Near Kooriyad, Malappuram, Kerala?
On May 19, 2025, chaos erupted near Kooriyad in Malappuram district,Kerala, when a newly built section of the six-lane National Highway 66 (NH-66) suddenly collapsed at around 2:30 pm, trapping four vehicles and injuring at least seven people. The disaster struck just 600 meters from the Panampuzha bridge, on a stretch built over a reclaimed, waterlogged paddy field—an area notorious for its soft, unstable soil and proximity to both the Panampuzha and Kadalundipuzha rivers.
The collapse brought down the Reinforced Earth (RE) Wall and Embankment onto the service road & adjacent fields, splitting the paddy land and forming a small hill of debris. This shocking failure, which occurred mere days before the highway’s scheduled inauguration, has spotlighted deep flaws in construction quality, site assessment, and project oversight—problems echoed by similar cracks and subsidence reported in Kozhikode and Thrissur. In the immediate aftermath, the Ministry of Road Transport and Highways blacklisted the contractor KNR Constructions and the project consultant, while suspending key project officials and launching multiple investigations at both state and central levels.
Cross-section showing weak subsoil and high water table beneath NH-66 embankment, leading to collapse.
The incident has not only triggered public protests and legal scrutiny but also forced a national conversation about the urgent need for scientific, site-specific engineering and stricter accountability in India’s infrastructure sector
Technical Analysis: Why Did the Collapse Occur?
1. Geotechnical and Structural Failures
Foundation Soil Inadequacy: The embankment was constructed over a paddy field with soft, waterlogged soils. Experts concluded that the foundation soils could not bear the high embankment loads, leading to settlement and collapse.
Negligence in Soil Testing: The concessionaire, KNR Constructions Ltd, failed to confirm ground conditions or improve soil bearing capacity before construction. This lack of due diligence was cited as a primary cause by both NHAI and the Ministry of Road Transport and Highways.
Water Seepage and Drainage Issues: Water seepage played a significant role, as cracks and ground movement were exacerbated by poor drainage and obstruction of natural streams during construction.
Probable failure mechanism indicating deep-seated shear failure beneath the embankment.
2. Design and Methodology Flaws
Unscientific Construction: The highway was elevated using gabion walls and soil fill rather than being built on pillars, despite repeated warnings from residents and local officials about the unsuitability of such methods for the area’s fragile, waterlogged terrain.
Ignored Expert Warnings: The Geological Survey of India (GSI) had previously warned the National Highways Authority of India (NHAI) about the risks of landslides and slope instability along NH-66, stressing the need for site-specific engineering solutions and thorough soil investigations. These warnings, however, were not adequately addressed. A detailed report by The New Indian Express highlights how GSI had flagged faulty road work on NH-66 in Kerala.
3. Oversight and Accountability Lapses
Consultant and Contractor Sanctions: Both KNR Constructions Ltd and the project’s independent engineering consultant have been barred from future NHAI projects. Key personnel were suspended, and remedial work is to be carried out at the contractor’s risk and cost.
Lack of Responsive Action: Complaints from residents and warnings from local bodies were dismissed by both the construction company and NHAI, who pointed to their experience rather than addressing site-specific concerns.
Environmental and Community Impact
Ecological Concerns: The construction obstructed natural watercourses, worsening waterlogging and destabilizing the ground. Soil from the project was dumped into nearby streams, further disrupting drainage and increasing the risk of collapse.
Community Warnings Ignored: Residents and local leaders had repeatedly called for a pillar-supported structure, citing the region’s history of waterlogging and soft soils. Their concerns were overlooked, leading to a disaster that vindicated their warnings.
Grassroots Action: In the absence of official intervention, locals spent their own resources to clear blocked streams, highlighting the lack of adequate environmental management by project authorities.
Legal and Regulatory Fallout
Kerala High Court Intervention: The Kerala High Court has taken serious note of the incident, directing NHAI to submit a detailed report on the causes and proposed remedies. The court criticized the pace and quality of highway construction in the state, demanding scientifically sound remedial measures.
Broader Scrutiny: The collapse has brought the role of state and central highway authorities under intense scrutiny, especially as similar structural issues have been reported on other stretches of NH-66.
Lessons and Recommendations
Key Takeaways
Mandatory Geotechnical Investigations: All major infrastructure projects in sensitive areas must include comprehensive soil and groundwater studies.
Adaptive, Site-Specific Design: Standardized solutions are inadequate for regions with complex geology; engineering must be tailored to local conditions.
Robust Oversight and Community Engagement: Transparent quality control, independent audits, and genuine engagement with local stakeholders are essential.
Environmental Safeguards: Projects should be planned to preserve natural drainage and minimize ecological disruption.
Regulatory Actions
NHAI has initiated expert reviews and will implement new guidelines to prevent similar incidents in Kerala and elsewhere.
Remedial work on the collapsed section will proceed under expert supervision, with costs recovered from the responsible contractor.
Latest 2025 Updates After the NH-66 Collapse
1. NHAI Orders Statewide Safety Audit of All RE Walls
NHAI has directed immediate structural and geotechnical audits of all RE walls and high embankments along NH-66. Early inspections have identified signs of cracking, settlement, and seepage in at least six stretches, including Ramanattukara, Edappal, and Chavakkad.
2. Contractor and Consultant Blacklisted
The Ministry of Road Transport and Highways has:
Blacklisted KNR Constructions for two years.
Suspended the Independent Engineering Consultant.
Ordered full reconstruction costs to be recovered from the contractor.
3. Kerala High Court Demands Scientific Redesign
The Court has ruled out temporary patchwork and mandated:
Revised structural design
Proper ground improvement
Third-party verification by IIT-Madras or equivalent institutions
4. IIT–Madras Invited for Technical Review
IIT–Madras is assisting with:
Slope stability modelling
Consolidation and settlement prediction
Drainage redesign
Failure mechanism reconstruction
Their final recommendations will guide the reconstruction approach.
5. Drainage Restoration Works Initiated
District authorities have begun clearing blocked natural streams, removing dumped soil, and restoring drainage paths — a critical step given the waterlogging-related failure.
Expanded Technical Insights: What Engineers Now Confirm
1. Inadequate Bearing Capacity and Shear Failure
The soft clay strata beneath the embankment lacked the undrained shear strength required to support the embankment’s vertical load and lateral earth pressures. Without preloading or reinforcement, shear failure initiated at depth and propagated upward.
2. Excess Pore Water Pressure from Rapid Construction
Rapid fill placement prevented dissipation of pore water pressure, triggering:
Lateral spreading
Deep-seated slip surface formation
Progressive settlement
Rotation and tilting of the RE wall
3. RE Wall Backfill and Drainage Deficiencies
Backfill material used behind the RE wall had high moisture content and low friction angle, violating RE wall design best practices. Poor drainage encouraged development of a slip plane.
4. High Water Table and Blocked Natural Drains
Altered subsurface flow paths increased uplift pressure and reduced effective stress beneath the embankment, accelerating failure.
Ground Improvement Techniques That Should Have Been Applied
PVD + surcharge preloading for consolidation acceleration
Stone columns to enhance bearing capacity
Pile-supported embankment in critically soft soil zones
Geogrids and geotextiles for reinforcement
Toe drains and horizontal drains to manage pore pressure
Instrumentation monitoring, including:
Settlement plates
Piezometers
Inclinometers
These measures are standard in soft-soil engineering and could have prevented the collapse.
Similar Geotechnical Failures in India
Similar geotechnical failures across India highlight systemic design and soil investigation challenges.
Chennai Outer Ring Road (2021): RE wall slip due to inadequate drainage
Bangalore–Mysore Expressway (2023): Early settlement on soft subgrade
Kochi Metro Approach Road (2018): Differential settlement in reclaimed land
Konkan Railway Slopes: Failures driven by rainfall and unstable terrain
These cases highlight systemic issues in soil investigation, design validation, and drainage planning.
Updated Engineering Recommendations for Future Projects
Mandatory detailed geotechnical investigation in wetlands and river basins
Independent technical audits for all high embankments
IoT-based monitoring of pore pressure and settlement
Public disclosure of soil test reports and design data
Community consultation in hydrologically sensitive areas
Shift from standard templates to site-specific geotechnical design
Why did the NH-66 road collapse?
Because the embankment was constructed on weak, waterlogged soil without necessary ground improvement, and drainage deficiencies led to failure beneath the RE wall.
Who is responsible for the collapse?
NHAI has blacklisted KNR Constructions and suspended the Independent Engineer. Further responsibility will be confirmed after official investigations conclude.
Could the collapse have been prevented?
Yes. Proper soil treatment, scientific drainage design, and site-specific engineering would have prevented the failure.
Is the NH-66 stretch safe now?
Traffic has been diverted. Final stability will depend on reconstruction following IIT-reviewed design and NHAI’s revised safety protocols.
Conclusion
The NH-66 embankment collapse is a critical reminder of the consequences of disregarding geotechnical realities, hydrological conditions, and scientific design principles. India’s infrastructure growth demands engineering grounded in rigorous investigation, site-specific solutions, and uncompromising oversight. The lessons from this incident must guide the future of national highway development to prevent such failures and ensure public safety.
