SLOPE PROTECTION AND DRAINAGE IMPROVEMENT AT TINDHARIA ON NATIONAL HIGHWAY 110 (PREVIOUSLY NH-55) IN DARJEELING DISTRICT OF WEST BENGAL, INDIA
Project Details
STRUCTURE TYPE
TerraLink® – A composite/ hybrid structure using TerraNail® and FreyssiAnchors® with GeoTrel® facing panels and High Adherence GeoStrap® 5 soil reinforcements
OWNER
The Ministry of Road Transport & Highways, Government of India and Public Works (Roads) Directorate, NH Circle – III
P. W. (Roads) Department, Government of West Bengal
CONTRACTOR
SSPL-Pioneer (JV)
CONSTRUCTION YEAR
March 2017 to January 2021
DESIGNER + CONSULTANT
- Reinforced Earth India Pvt. Ltd.
HIGHLIGHTS
- A challenging landslide protection and road widening project was successfully completed on NH-110 (previously NH-55) near Darjeeling in West Bengal, India.
- Innovative TerraLink® technology was used by Terre Armée India to build this engineering marvel with limited available space at base (2m to 5m), using high adherence GeoStrap® directly and mechanically connected with GeoTrel® facing with TerraNail® and further strengthened using pre-stressed FreyssiAnchor® (completely re-stressable cable ground anchors) in this project to stitch the new construction with the existing hill profile.
- The mechanical connection system adopted for this project as per codal provisions was an essential requirement to ensure transfer of loads between facing, soil reinforcement and anchors/nails in high seismic zones and for the overall stability and greater performance of the reinforced filled structure.
- Highly compressible and durable (with heavy galvanisation of 500 gsm) fusion welded steel grid mesh (made of minimum 8mm diameter bars) was used to withstand higher deformations to meet any internal settlements.
- Safety and quality were top priorities for the project. Terre Armée India adopted the safest construction method for this unique project.
- Reduction of backfill quantity (up to 10x) led to cost optimisation and minimised environmental impact.
- The improvement of surface and sub-surface drainage systems ensured the structure’s long-term performance.
- The structure has performed well under seismic load when recently subjected to an Earthquake of 5.1 magnitude.
Very limited space was available at the base of the valley for constructing such tall retaining structures using traditional method. Innovative idea was “need of the hour” to suit the requirement of stabilising the existing unstable slope and to widen the road. This prompted Terre Armée India to use their innovative TerraLink® technology (shored or composite Reinforced Earth® structure). TerraLink® was designed after conducting a detailed global as well as compound stability check and finite element modelling of the collapsed slope to provide a robust and engineered structure, which can withstand differential settlement and impact from dynamic loads. The use of mechanical connection system between the soil reinforcement and soil nails ensures greater stability of the shored Reinforced Earth® structure and superior performance under extreme loading conditions. TerraLink® also optimized the cut and fill volume in this project. Internal and external drainage was also improved to channelize the run-off in the area.
The S2 Structure, which stands supreme at 102.8 meters, makes Project Tindharia the world’s tallest Reinforced Earth® structure and an acme of tall, steep slope soil reinforcement engineering. The innovative and sustainable TerraLink® solution used in this project has resulted in the widening of existing roadway, slope stabilisation, drainage improvement and rehabilitation of the massive landslide at Tindharia.
This project’s landmark success will surely instil greater confidence amongst the Engineering Fraternity in India as well as in various parts of the world and encourage them to take up more complex and challenging civil engineering projects like this in the future.
