Rainforest Road Repair and Rehabilitation with Stabilisation

A limited amount of suitable aggregate and resources in the Riau province of Indonesia can challenge road builders, but Indonesian contractor PT. Harap Panjang overcame the obstacles on a recent project.

The province rests in a tropical rainforest. The 2600mm of annual rainfall take a toll on the area’s roads, particularly those developed by oil company PT. Chevron Pacific Indonesia. The remote roads were built to service Chevron operations who find them every bit as necessary as the oil company.

The challenge is in rehabilitating the roads. The roads are numerous, with significant improvement and or rehabilitation are required. However, good aggregate is not available in the province; it would have to be transported from another island (ie Karimun, Tanjung Pinang or Java) that hundreds of kilometres away. Such efforts have substantial cost and environmental impacts.

The problems were overcome on a network of recently rehabilitated roads in Riau province. PT. Harap Panjang developed a soil stabilisation and reclamation process offering cost and environmental benefits, and which has also made the roads more stronger and safer.

PT. Harap Panjang started as a general contractor in 1975. The Indonesian company now specialises in road construction, including earthwork, road foundations and paving. In 2010 PT. Harap Panjang first implemented the pavement rehabilitation and soil stabilisation process because of its many benefits. “We are experts in design and pavement stabilisation construction,” said Arif Widiyanto, operation manager with the company. “In addition to the road construction and rehabilitation, we also have expertise in the development of operating procedure and technical specifications. We work with the Indonesian Road Research and Development Center to provide guidance regarding the pavement stabilisation process.”

Indonesian governmental agencies support stabilisation as this technique suits the conditions and offers improved performance while meeting cost targets. “To produce a pavement of a certain structural number, stabilisation can achieve cost savings of 35-50% compared to conventional construction methods,” Arif said.

The current work is called a “critical road improvement project” by Chevron. It is essentially an ongoing improvement that started in 1999. It has continued to grow and now has been modified to include stabilisation technology.

“The objective of the project is to service rig operations and move people and equipment more effective and safely,” Arif said. “Reducing the cost of road maintenance is another consideration.”

The rebuilt roads are safer, which is the ultimate goal of all involved. “The existing road is very dusty when dry, but also can become slick when the rain arrives,” Arif said. “Chevron wants to improve health, environmental and safety performance in their operation to achieve zero incidents and zero oil spills. That made road improvement very important.”
The environmental impacts include the in-place recycling of material, a considerable cost saver. “Aggregate of the required quality is too far from the project site,” Arif said. “Without recycling, we would have to import aggregate from another island at a distance of more than 800km.”

The existing pavement material (soil beneath it and granular stone) is suitable for a proven stabilisation technique using cement or lime. Arif said stabilisation, in part because of the additives used, has additional advantages in the rainy climate. The process improves the engineering properties of the pavement material, including factors such as plasticity, swelling, gradation. Stabilisation is a very quick construction process compared to traditional road reconstruction methods and also improves the pavement modulus. Other benefits are that it enables durability and helps resist water penetration, as well as promoting sustainable development as recommended by the Indonesian government and Chevron.

A key project under way will stretch over three years. It involves reclaiming around the cities of Minas, Duri, Bekasap and Petapahan in Riau province. Crews this year will reclaim a hundred km of the road, which is expected to last 15 years before needing to be rebuilt. “The existing road generally consists of compacted soil or aggregate as the base layer, with a thin layer of cold mix as the surface layer,” Arif said. The existing pavement base layer often doesn’t have the required strength for the increasing traffic volume and weight of vehicles associated with wellpad development and rig operation. The existing pavement is in bad condition, with depressions, potholes and dust,” Arif said.

The reclamation process is now well proven for the conditions and the contractor has had considerable experience with the technique. Crews place 60tonnes of binder material/day. Portland Composite Cement and hydrated lime are normally used as the binders, and these are often combined to reduce pavement material plasticity. A special cement spreader truck places the binder material in front of the Caterpillar Paving’s CAT RM500 B Reclaimer/Stabiliser.

The machine is used to make two passes. First, it completes the dry mix process—including pulverisation of the existing cold mix—at a pace of 4-5m/minute and a depth of 200-250mm. Next comes a wet mix process, which re-mix and apply water to achieved optimum moisture content.  The RM500Bhas a pace of 7-8m per minute and a depth of 250-350mm while making the mixing passes. “The power is good at that depth,” Arif said. “The operator can set the depth and spray water aplication  and go.”

The RM500B has proven to be reliable, effective and productive in this application, while its manoeuvrability has also provided an important advantage due to tight working conditions in some areas. The machine’s relatively slim design has been another benefit as this allows the unit to be transported to site without the need for special permits in Indonesia, reducing the amount of paperwork the contractor has to deal with. Dealer support is important, as is the training provided at the local CAT dealer, PT Trakindo Utama.

The RM500B is used to make one pass for the initial pulverisation stage and then makes a further two passes for the soil stabilisation phase. Two compactors are used a few metres behind the RM500B. First is a 20tonne padfoot compactor, which makes four vibratory passes on a medium setting. A 12tonne smooth drum compactor then follows making two medium vibratory passes as well. With these compaction machines, tests have shown the contractor can easily achieve the required density of 95%.

Using this process meets Chevron’s targets for lowering the environmental impact of road construction. The method allows the roads to be rehabilitated (recycling), instead of rebuilt, substantially reducing the amount of fuel and new material required on the job site. The aggregate is recycled too, with fuel saved by not having to haul material from another island hundreds of kilometres away. Meanwhile, providing a smoother road will increase the lifespan of any rig and vehicles using the route. And the life expectancy of the road helps to ensure that no further major works will need to be carried out for another 15 years. The roads also are safer for Chevron workers providing the most important sustainability effort of all. (Resource: https://www.worldhighways.com/feature/rainforest-road-repair-and-rehabilitation-stabilisation