CASE HISTORY: Paramesh wall for mountain road to Al-jais, Ras Al Khaimah, UAE
REINFORCED SOIL RETAINING WALLS / SLOPE PROTECTION
Product: Terramesh System, ParaLink, Geotextile.
PREAMBLE. Highest peak in UAE, Al Jais is located in the Northern Emirate of Ras AL-Khaimah which is 25 Km away from the main town. Currently Al Jais is surrounded with some local people’s houses, local animals and is not much popular. But, the place is 10 degrees colder than the main cities in the UAE & hence the project owners decided to make a visitors spot there which will be able to attract the stream of tourists.
Currently, a tourist destination is planned with a resort to be developed at top. In later stages, the project owner is ambitious about developing further tourist facilities like hotels, Ski hill, golf course, & cable car arrangement etc.
PROBLEM. The proposed site comprises of 36 Km of road, which is rising up to a height of 1700 meters (5577 feet). As it is one of the highest peak in UAE, construction is ought to be challenging due to large quantity of earth works involved, difficulty in access, moving up construction machineries etc.
Huge amount of cutting & backfilling is required. Mostly, the materialfrom cutting is to be used for filling.
In particular due to mountainous morphology of the area, many sections run alternatively through large steep embankment fill sections and slope cuts and retaining structures.
The exiting site condition required the need to have a nearly vertical retaining structure between chainages 20+350 to 20+575, the highest 32 m section being at chainage 20+475. The original solution of 34 degree filling was unfeasible at this location, which otherwise could have even extended filling above the bottle road.
Further, this site receives occasional rainfall & snowfall. During the rains, flash floods are very common this this region which even washes away the entire road and underlying embankment. Hence, it is critical that the high retaining structure should also be naturally free draining and stable against the potential affect of additional water forces behind the structure otherwise.
SOLUTION. Maccaferri was subcontracted for design, supply and construction supervision assistance of the 32 m high retaining wall. Out of the different retaining wall solutions with Maccaferri, the ParaMesh system was chosen that gives unmatched advantages required specific to a mountain road project. Typically, ParaMesh is a composite soil reinforcement system with different types of soil reinforcement used.
Maccaferri Products used:
• Terramesh system, a double twisted steel wire mesh unit which forms the facia with the aesthetics of gabion but also with the reassurance of a secondary soil reinforcement to prevent sloughing failure of wall face.
• ParaLink 300, a high strength polyester geogrid (Primary reinforcement) with its vertical spacing varying from 1 m (at wall bottom) to 2 m (at wall top).
The constructed total facia area of retention is 3670 m2 , ranging in height between 5m to 32m.
The site strata primarily consisted of sedimentary rock which varied from weathered to hard rock condition and patches of soil deposits at some locations. The backfill material used between ParaLink geogrid layers contained relatively larger particle sizes; thanks to the better polyethylene coating on the polyester core of the geogrid material. The possibility of using local material like high graded backfill material and boulders for gabion facia resulted in considerable cost savings in the project.
Being deep valleys, creating access for construction equipments at wall bottom location was really challenging and hence progress of ParaMesh wall construction was slow initially. Construction started at valley no-1 as a trial. From that experience, the specific requirements were identified and then work progressed at valley 2 & 3 parallel. Productivity increased as wall height progressed resulting in longer stretches for compaction.
The actual site conditions varied a lot from the design conditions that resulted in few design revisions, but owing to the flexibility of the Terramesh system, the units could be easily modified/ deformed at site to match the site conditions.
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INFO : http://www.maccaferri.com/it/