Al Sowah Island, Abu Dhabi, UAE
ESC was involved in the execution of various temporary retention works by providing with cost and time effective sheet pile solutions. These include providing sheet pile or H pile solutions for District Cooling Plant, Sewer laying or repair pits, dry platform for constructing bridge foundations in the form of cofferdam and pile caps of bridge foundations
TEMPORARY RETENTION SOLUTIONS FOR VARIOUS INFRASTRUCTURE PROJECTS ON AL SOWAH ISLAND, ABU DHABI, UAE
Al Sowah Island forms an important part of the Abu Dhabi government’s Plan Abu Dhabi 2030, under which various infrastructure development works are planned to be carried out to make Al Sowah Island a Central Business District. Various infrastructure works being carried out include 13 bridges, a district cooling plant (DCP) besides constructing various residential and commercial facilities. Kharafi National was appointed the Main Contractor while Al Naboodah National Contracting Group (ANNCG), was appointed the Sub Contractor to carry out many of the above listed projects.
ESC was involved in the execution of various temporary retention works by providing with cost and time effective sheet pile solutions. These include providing sheet pile or H pile solutions for District Cooling Plant, Sewer laying or repair pits, dry platform for constructing bridge foundations in the form of cofferdam and pile caps of bridge foundations (refer figure 1). ESC has carried out all the design and supply works for the above as per the British Standards and has successfully installed them. The following sections illustrate the details of some of the important projects.
In general, the ground conditions at Al Sowah Island sites consisted of medium dense silty sand until bed rock (Calcarenite) is encountered at 5m depth. However depth of bed rock varies consistently.
Modeling was performed using an effective stress analysis based on BS8002, using the analysis software ReWaRD. The design of the sheet pile system was performed in accordance with the requirements of BS5950. Anchors were designed based on BS8081, which is a working load design standard.
Lifting Platforms for Bridge 12 & 13
The first phase development of Al Sowah Island is made up of major infrastructure works, including construction of 2 bridges – Bridge 12 and 13, leading to the island. For construction of the bridge foundations, a dry platform was needed. Therefore a temporary retaining system in form of sheet piles and ground anchors was proposed. The sheet piles provided a retaining wall for the temporary fill material and kept a clear channel for water flow and small craft movement. After construction of the bridge foundations, the sheet piles and anchors were removed. A total of 656 sheet piles (FSPIV and CR13575, 12m), which corresponds to 577 ton were installed at this project site. 132nos dual tie rods (Y25mm Grade 460) were installed with concrete blocks for additional lateral support.
Picture illustrating the projects & their locations across Al Sowah Island for which ESC has designed, supplied and built the temporary retention system
1-Sewer repair or laying work; 2- Bridge foundation for Northern Access; 3- District Cooling Plant, Pump Station and Pile caps; 5-Manholes ; 6 & 7-Lifting platforms for Bridge 12 & 13; 8- Edge protection at Bridge 1;
9-Navy bridge removal
District Cooling Plant, Pump Station & Pile Caps
The construction of Cooling Plant and a Water Tank required excavation to 8m depth. Temporary retaining wall in the form of embedded sheet piles in combination with one level ground anchors was constructed to facilitate the required excavation. One side of the wall was supported using tie-backs with concrete blocks, due to site constraints. A total of 1130 sheet piles (FSPIV and NSP3W), which corresponds to 1140 ton were installed at this project site. 52 and 80 nos of grouted anchors and tie-back anchors with concrete blocks respectively were installed for additional lateral support.
For the construction of Pump Station excavation to a depth of 15m was required. However, the working platform was lowered by means of a sloped excavation to limit the total length of the sheet pile to 13m. A total of 260 sheet piles (NSPIIIw) which corresponds to 276ton was installed along with 130nos dual tie-back anchors (Y32mm Grade 950).
In addition to the above works, ESC also carried out the installation of temporary retention system in the form of kingposts (H-beams) and wooden in-fill panels for construction of the pile caps. A total of 600m of wall was installed for this purpose at various locations spread across the District Cooling Plant site.
Sewer Repair or Laying Works
After construction of the sewer system on Al Sowah Island, 3 leakages were identified across the Al Sowah Island which was to be repaired. The leakages were at a depth of about 4.5 to 5m from the existing ground level. Keeping in view the existing structures, a temporary retention system in the form of embedded sheet piles with one level of strutting has been proposed to facilitate the required excavation to repair the sewer leakages. At another location, similar retention system was adopted for laying the sewer pipe underneath a highly sensitive 400kV Transco cable. After the sheet piles were installed, the sewer pipe was driven successfully.