Filling the “Punta Negra” Dam (San Juan, Argentina) forced the construction of a new road on the lake’s perimeter to give continuity to the route RP N°12 re-establishing the connection with the “Caracoles” Dam, whose original layout was below the water level of the reservoir.

The 24km road´s construction, included more than 3 million m3 of embankments, 7 new bridges, more than 70 large culverts and almost 100,000 m3 of rock excavation.

Strong winds (such as the Zonda) blowing on the wide water’s mirror made by the dam will generate waves that could damage the embankments’ slopes (up to 40 m height and 1V: 1.5H). For this reason, the original project used to cover the slopes with rock armour.

However, the increasing difficulty to obtain rock -sufficient quantity and quality- also generated a strong environmental impact and at least one year construction´s schedule extension. This was the contractor’s motivation to look for other alternatives that allowed to meet the deadline and presented an efficient performance against the waves.

The aim of this paper is to describe the design criteria and the overcome´s challenges of the BetonFlex® system in replacement of the traditional rock.  BetonFlex® is a continuous and flexible protection which consist in a uniform rectangular pattern of square truncated pyramidal concrete blocks, casted into a polypropylene fabric linked together with a network of high-strength polypropylene loops (loop matting).

The BetonFlex® concrete block mattress (CBM)  was made from a woven geotextile PlusTex® T 80/60 HLT SCL, which has 80 kN of longitudinal resistance (MD: machine direction), especially manufactured with additives to provide UV radiation and thermo-oxidation long term protection, improving its durability. The fabric has more than 2500 small circle loops per sqm that guarantee the anchoring of the 30cm high concrete blocks.

More than 7,500 CBMs where precasted in site at a specially built facility for this purpose, which had 8 tracks of 150 m each, a gantry crane and a formwork with steam curing system that allowed a fast stripping and movement of the CBMs. Every CBM had 65 square blocks of 0.40 m on each side, covered 12 m2 and weighed more than 7 tons each.

The selected solution included a new anchoring system to fix the CBMs to the embankment by using galvanized steel pegs into a special designed block that acts as a transfer beam. CBMs lifting method was optimized several times due to strong winds risks, making it able to work faster and more safety. The regular yield was 60 CMBs per day (build, transport and place)

Finally, the environmental impact that would have meant dynamiting more than 1 million m3 of mountains for traditional rock armour was avoided by using a geosynthetic erosion protection system.