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Challenging Construction of two huge shafts by diaphragm walls – new dimensions for Africa


Medium: conference paper
Language(s): en 
Conference: 19th International Conference on Soil Mechanics and Geotechnical Engineering (ICSMGE), 17-22 September 2017, Seoul, South Korea
Page(s): 2727-2730
Year: 2017
Abstract: The main cables of the new suspension bridge under construction in Maputo (MZ) are anchored inside a shaft built by diaphragm walls of 1.20 m thickness. With an outer diameter of 50 m and an excavation depth of 17.50 m and 37.50 m, these shafts are among the largest being constructed in the world in the last years. The structural design follows Chinese Standard, South African Standard as well as Eurocode design methods that is used for verification of the original design. The existing geology is characteristic for this coastal region with mainly medium-sized sands, soft mud stone underlying by sandstone. Soil improvement in the upper layers by mixed-in-place piles and underneath the tip of the panels by jet grouting have been required. The concrete with 40% of fly ash and a specially designed superplastizer retarder for a 16-hour retarding has been carefully selected and tested. One major part of the work onsite is the quality control and verification. For the diaphragm walls testing methods have been among others ultrasonic testing in the open trench, CSL testing after concreting and visual inspection of the wall after excavation. The excavation inside the two shafts gave a feedback of the records taken before.
diaphragm walls shaft

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