Road Rehabilitation in Extreme Conditions
In mountainous, tropical conditions of Andes, Neoloy® Geocells enabled road rehabilitation which doubled design life.
Oil tankers and heavy construction equipment of the Hocol Oil Company traverse a 18 km unpaved access/haul road to remote oil drilling pads in the Andes Mountains of Colombia, over soft sandstone subgrade (CBR 3.9%) with up to 15% slopes.
The tropical climate and steep topography subject the road to severe erosional forces. Heavy winter rains erode side slopes and embankments, which clog drainage ditches, causing even more runoff and surface erosion. In the summer the hot sun dries out soils and infill materials. This accelerates erosion and loss of fines, generating dust pollution, while leaving even less of the road surface.
The 150 ton tanker trucks try to avoid stopping as they travel up the mountain. Yet, they get stuck so frequently – even in the dry season – that tractors are always on standby to tow them out. Repairs along the route are carried out on a continuous basis.
Hocol needed an effective rehabilitation for a more reliable and durable road – including roadside slopes, drainage ditches and embankment walls – for safer, more efficient and economic operations.
Conventional pavement design over soft subgrades requires large amounts of quality aggregate, which is expensive to import to this remote region. Road design must also mitigate erosion and aggregate shifting to improve its design-life. Gabion slopes and embankments while efficient, are expensive to construct and repair. Concrete slabs used for drainage ditches are easily fractured by trucks. The logistics and cost of rehabilitating this road using traditional methods are exorbitant.
Neoloy Geocell Solution
Neoloy Geocell was chosen due to its ability to resolve several problems at once, all with local marginal infill.
- Unpaved road – the design improved the subgrade bearing capacity (>5.7%) due to the modulus improvement factor of Neoloy reinforced material (MR=42 MPa). Pavement thickness was 15 cm Neoloy Geocell filled with quarry waste and infill from the failed road, and 5 cm overfill.
- Slope protection – perforated 7.5 cm high Neoloy cells protected slopes from erosion, utilizing stake anchors for stabilization and top soil infill.
- Gravity walls – used medium size perforated 20 cm high Neoloy cell for unstable steep slopes with local granular infill and topsoil for the green fascia cells.
- Drainage ditches – 60 cm wide V-channels (1:1 slope) were constructed with 7.5 cm high Neoloy Geocells utilizing concrete infill for maximum protection.
The bottom line was the full satisfaction of the client and users. Drivers interviewed on-site were amazed at how Neoloy Geocells improved vehicle handling and their control of the road. Trucks driving over the Neoloy reinforced sections simply did not get stuck.
- Pavement structure reduced by 50%
- Road CBR increased by 93% from 18% to 34.8%
- Improved road performance (allowable rutting limit 5 cm)
- Design life doubled – 10 years instead of 5
- Increased factor of safety even at 50% increase in traffic
- Confined drainage system
- Significant reduction in repairs and maintenance
- Improved haul operations and efficiencies