Assam & Meghalaya, India | IL&FS
The Jorabat Shillong Expressway Limited (JSEL), Guwahati has been entrusted four laning & development of Jorabat – Shillong section by NHAI. The challenge was to convert an existing 2-lane highway into a four-lane expressway in the terrain that is hilly and dense. The region also receives the highest rainfall and part of the highway is among the wettest regions in the country.
During our visit to the site, It was observed that the particular section was in cutting and the cutting has exposed rock faces that were intact in some locations and fragmented in few locations. The exposed rock surface on the sloping face is always subjected to disintegration by various causes such as plant action, thermal expansion, wind, freeze and thawing action of the pore water, hydrostatic pressures etc. The disintegration of parent rock leads to formation of rock pieces, boulders and debris and they easily detach from the bed rock and will slide over the slope. Such fall of rock happens catastrophically at random locations without giving prior warning. During monsoon seasons, the situation gets worsen that rock falls may become vary frequent.
To prevent the rockfall from the side hill slopes on to the road, TechFab india suggested TechFab Metal Netting with special 5.5 Twisted Zinc + PVC coated wire mesh with Mesh type ( 8×10) along the slope and it was anchored by using raised anchorage system at top and bottom.
Selection of rockfall mitigation was done in such a way that the small or medium size detached loose boulders are guided through the drapery/netting system and it shall be reach at toe of slope. And that boulder, debris shall be remove periodically as part of maintenance to accommodate further disintegrated rocks.
The height of cutting to be protected was 6m to 15m. The slope angle of cut section is varying from 55º to 70º. The rockfall protection system will prevent the fall of any rock pieces directly on road and it will guide the boulder to fall at toe of the hill slope and hold the disintegrated rocks, where the bottom anchors are placed.
The special 5.5 twisted wire mesh is made of Heavily Galvanized steel wires with PVC coating. The twisting is done mechanically and is non-raveling in nature.
Advantages of using TechFab Metal Netting :
High loading capacity.
High flexibility.
Uniform distribution of the tension.
Excellent buffering performance.
Corrosion and rust resistance.
Durable and long service life.
For this project, special five and half twisted metal wire mesh netting was produced. Client was happy with quality of material supplied and prompt support from our team. Project was completed within given timeline.
It has been 7 years since project is completed. Rock fall protection system faced many worst monsoons still and the system is working as per the project requirement and desired by the client.
