Several slopes and reinforced earth (RE) walls built on NH 66 in Kerala are vulnerable to landslips and cave-in, cautioned an expert investigation.
The investigation report submitted to the National Highway Authority of India last week has flagged the vulnerable segments on the road stretch. The damage to the road stretch had led to a public uproar in the State.
The panel conducted slope stabilisation assessments at 27 chainages along the Thalappady-Chengala to Kadampattukonam-Kazhakuttam corridors, and examined the stability of RE walls on 12 stretches between Thalappady-Chengala and Kadampattukonam-Kazhakuttam.
Weep holes absent
In the Chengala-Neeleswaram corridor, the critical deficiency of the “absence or insufficient spacing of weep holes, which are vital for drainage” was identified. The intense rainfall in the region and the lack of adequate drainage posed a substantial risk of “progressive structural failure despite the apparent surface stability.” The “location should be considered a priority intervention zone given its vulnerability and alignment with high-risk geotechnical conditions,” it said.
The chainage 95+700 to 96+200 in the Neeleswaram-Taliparamba corridor, where a slope failure had happened, warranted urgent intervention to prevent widespread structural damage and traffic disruptions. Peeling or delamination of shotcrete, destabilisation of slope facings, and progressive slope failure were noted in the chainage 98+600 to 98+800.
The slopes at chainage 130+150 failed due to the improper methodology/ construction sequence followed for cutting the slope, as well as the method of soil nailing. The chainage 129+900 to 130+300 was vulnerable to gullying and progressive failure following rainfall. In the Taliparamba–Muzhappilangad corridor, restricted water movement across the reach posed significant risks to the stability of highway infrastructure in the 148+200 to 149+350 chainage, the report noted.
Soft subsoil
The embankment at Kooriyad collapsed as the “soft, highly compressible fluvial subsoil beneath the embankment could not carry the intended earth loads.” The treatment of the reach as a paddy field, after ignoring its fluvial origins, was a major oversight. A viaduct or bridge design with deep piling would have been ideal at the place, the panel felt.
Significant lateral deformation of the RE wall on both approaches of the Neeleswaram RoB at chainage 93+700 was also observed. “The inadequate compaction of backfill, weak foundation soil, use of marginal fill material, accumulation of excess pore pressure due to poor drainage and construction-related deficiencies” could have led to the damage. The RE wall of the flyover at chainage 117+490 to 118+120 faces the risk of “excessive settlement,” it pointed out.
Groundwater table
The RE walls in some chainages of the NH at Taliparamba–Muzhappilangad, Kappirikkad–Thalikulam, Thalikulam–Kodungallur, Kodungallur–Edappally, Kollam bypass–Kadambattukonam, and Thiruvananthapuram bypass section (Eenchakkal) may fail if the rectification measures are not implemented. The groundwater table was found at ground level in some segments of the NH at Ramanattukara Junction, where the Valanchery Bypass starts and Kadambattukonam–Kazhakuttam and Valanchery Bypass–Kappirikkad, it said.
The panel has suggested continuous monitoring of the RE walls to ensure that the settlement remains within permissible limits.
Published – August 10, 2025 07:35 pm IST
