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Finishing Touches at Ras Laffan LNG Port Expansion, in Qatar
The civil engineering stage of the first phase of the major expansion of the LNG Port at Ras Laffan, Qatar is nearing completion after almost 3 years. Specialist marine and costal engineering plant hire company, Abeko BV, has the contract to provide the machinery and operators required by Van Oord BV for the construction of the 22,5 km of causeways and breakwaters. They are now applying the finishing touches before handing over to client for fitting out. The contractors are currently undertaking the final surveys and, as appropriate, are working with the Abeko team to do any remedial and finishing work to ensure that all constructions are in accordance with design specifications. This work calls for precision working in order not to disturb material already in place both from a variety of land-based equipment and from the sea, where an O&K RH90C mounted onboard the Abeko Server 1 is helping with final underwater profiling of the breakwaters. Over 10,6 million t of local rock, together with a further 4,2 million t imported from the United Arab Emirates, has been put in place, either by side dump barges or by dump trucks. Over 1 million m³ of concrete was used by the prefabrication yards for production of 185 000 precast concrete antifers and 36 000 concrete acropods, which were for the armor layer construction of the breakwaters. The antifers range in size from 1,5 m³, 3,0 m³ and 3,5 m³. The acropods are from 3,0 m³ to 5,0 m³. The rock and precast concrete elements were used to profile and protect the land reclaimed from the placing of more than 20 million m³ of dredged limestone and 25 million m³ of offshore sand. Throughout the project, the contactors have utilised 45 heavy-duty excavators and high-capacity crawler cranes, 40 rigid and articulated dump trucks and 20 wheel loaders as well as other support equipment. The number of people on site deployed by Van Oord and Abeko peaked at over 700. Work has progressed non-stop, 24 hours a day, 7 days a week. Precision Working Typically, the seaward-side of the embankments comprise 3,0 m layer of selected quarry stone up to 500 kg; a 1,8 m layer of heavier 500 - 2000 kg rock and a 3,2 m protective layer of antifers or acropods depending on position. At the foot, there is large breakwater toe with 5 m extension. However, such is the variation in the dimensions, according the water depth and where additional protection is required such as on the roundheads against possible ship impact, that there is nothing “typical” about the project. This is why it has proved to be so challenging. The challenges for the contractors were many and included the scale of the project, the time restraints, logistics, the many variations, very demanding quality control for materials and the construction tolerances (as little as ±0,2 m). To achieve this, they had to deploy the very latest technology, advanced computer aided systems, sophisticated, heavy-duty machines configured specially for the works and a team of highly skilled operators. Men and Machines Critical to the works has been the 52 m long, 470 t Abeko Server 1, which, with 30 m long spud legs, is able to work in water depths of up to 24 m. The large deck area of 6 m x 40 m allows the use of very large, heavy-duty excavators. For Ras Laffan, the machine selected was a 230 t O&K RH90C with triple boom, equipped with a 30 m boom and GPS Prolec Digmaster system enabling precision working in deep water. Land-based equipment assisting in the finishing work was varied. In the placement of antifers, 127 t Hitachi Zaxis 850s are used. These are equipped with specially designed rotating grabs to pick up and position the heavy and large dimensioned blocks, which could be up to 3,0 m³. Other Hitachi ZX850s are configured with long reach booms to give a 30 m reach. These were modified by Abeko with a special float arrangement on the end of the stick to improve handling. This was essential to enable the necessary precision when placing large rocks and concrete blocks under the water. Apart from the GPS Prolec Digmaster, some of these excavators also feature a sonar radar system to provide the operator with underwater vision. All available equipment is being put to use in the final stages. Kobelco CKE 800 crawler cranes with an 80 t lifting capacity, work alongside 130 t Hitachi ZX870 excavators placing antifers as quickly as possible. These are delivered from a nearby stockpile, in a continuous flow, by Cat 988H and Cat 966H wheel loaders with front end handler. Cat articulated dump trucks and rigid dump trucks are being used to haul the final batches of armor rock from the quarry stone stock pile. Highway trucks bring the material into the site. Working the stockpile is a Komatsu PC 600 excavator as the primary loader. Although centrally positioned, such is the scale of the project that the haul distances can be several kilometres in length. The travel distances, extreme heat, humidity and a dusty environment are very tough conditions for the machines, the operators and workers. Key equipment in the Abeko fleet includes: (4) 160 t Hitachi EX1200/5 with triple boom giving a reach of 24 m. The track frame on these has been extended and widened for extra stability. Additional excavators and other equipment was brought in as required from the extensive Abeko fleet which comprises over 150 pieces of equipment, all selected specifically for marine and coastal engineering works. Equipment available includes multi-purpose self-propelled spud barges; heavy-duty tracked excavators; wheeled excavators up to 75 t; wheeled loaders up to 90 t; multidockers; bulldozers; articulated dump trucks and remote controlled tracked loaders. Almost all the machines have been extensively modified for the type of work they are required to do. It was essential, therefore, that they ensured that the equipment was reliable, and that the operators had the necessary skills to work with the advanced technology used in placing the various materials. The operating environment in Ras Laffan is not the best for plant and equipment. Servicing was, therefore, deemed a priority. As the machines were virtually on-call at all times, service scheduling was critical. Apart from fully equipped service vehicles used by technicians skilled to work on a wide variety of machines, Abeko also built a fully equipped workshop with 10 full-time engineers and 2 full-time site/workshop supervisors. This provided the essential 24 hour day coverage, 7 days a week. To minimize delay in servicing and repairing the equipment, Abeko had over €1 500 000 ($2,4 million) worth of spare parts on site at all times. Logistic Management As a global plant hire company, this can mean shipping equipment from different parts of the world as well as making any necessary modifications. Within the Abeko range of equipment there is no such thing as a “standard” machine. This is what differentiates Abeko from most other plant hire companies. Almost every piece of equipment has been extensively modified to meet the challenging work demanded from them. Typical modifications include wider, longer undercarriages on excavators for increased stability and additional counterweights to facilitate handling or large, heavy-rocks and precast elements. Dump trucks typically have Hardox bodies and electrical circuits given additional protecting from the harsh environment. Some components such as alternators are also upgraded. Abeko also uses many different boom configurations and will even make their own modifications to booms for special applications. Their self-propelled jack-up barges are also fully equipped with accommodation units and catering facilities to enable extended operations offshore to maximize available time. Working in Partnership The contract, valued at $2,4 billion, by Hofstade-Aalst, Belgium - Qatar Petroleum, is being undertaken by Jan de Nul Group in a 50/50 joint venture with Boskalis. Van Oord BV is under contact to the main contractors to undertake construction of the breakwaters and associated works. For many years, Abeko BV has had a close association with Van Oord providing vital equipment and support services. |
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As the first phase nears completion, the massive volume of material deployed is evident by the several kilometres of structures standing several meters above the water line.
There is also more than 900 000 m² of geotextiles incorporated into the structures and the causeways and breakwaters are finished off with 3,4 m high crown walls and 50 m wide x 2,15 m deep reinforced road slabs (typical) for which more than 170 000 m³ of concrete was poured.
On the harbour side, the composition is a 1,80 m layer of 500 kg quarry stone; a 1,15 m thick under layer of 100 - 500 kg quarry stone and an outer layer, 1,80 m thick, of armor rock (500 - 2000 kg).
To the untrained eye, the placement of the antifers seems random, but, in fact, they are carefully placed to ensure their effectiveness in dispersing wave energy and to prevent back-scouring.
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