Tunnel design in the design and construct context—the Pergau experience, Malaysia
The 600 MW Pergau Hydroelectric Project in Northern Malaysia is being constructed as a design and construct contract. 33 km of underground tunnels and shafts and a large underground powerhouse complex were to be constructed in accordance with the principles of NATM. Limited site investigation was enhanced by additional investigations put in hand as construction began. After preliminary designs were prepared a site design team was set up to supervise and direct the excavation phase. Although tunnelling started well investigations indicated low rock stresses at depth which was verified as the tunnels neared the cavern itself. Following this verification a major review of the design of the high pressure system was carried out resulting in significant last minutes changes to tunnel and shaft geometry and lining design. In the design and construct context the contractors construction requirements must be dealt with as well as the evolving geological conditions which requires close cooperation between all parties involved to ensure the smooth evolution of the design.
KeywordsDesign and Construct NATM Low Rock Stresses Hydropower
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