A Constructability Problem in a Deep Shoring System

Hakan Köpüklü, Onur Ekli, Önder Akçakal, Hilmi Turan Durgunoğlu

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Abstract



The construction of deep excavations and retaining structures for the deep basements and infrastructures has frequently been implemented in İstanbul. Primary design concerns for underground construction are the protection of adjacent buildings, properties of the project site, and planned structures; thus, the appropriate selection and design of the retaining wall system are critical for the project’s success. This case history presents the design and construction details of the watertight retaining wall for the seven levels of basement which required an excavation depth of up to 30.0m. Considering the presence of high groundwater level in the project area, the temporary retaining system initially consisted of secant bored piles with a diameter of 1.0m and 0.2m overlapping, supported by multilevel prestressed anchors along the entire site perimeter. During the construction of the secant piles, it was seen that the mechanical properties of the encountered rock units of Trakya Formation were better than the expected in design phase, and therefore piles could be constructed with a length of approximately 25.0m which was 10.0m shorter than the project lengths but socketed into the hard rock strata. The design of the bottom part of the retaining wall was revised utilizing shotcrete with wire mesh (t=0.35m) and additional prestressed anchors. The plan view of the system is a rectangular shape, the inclinometer measurements have been taken during the construction phases, and the lateral displacements are compared with determined ones in design. In three sides of the retaining system there were very small displacements; however, in one side the excessive displacements are measured upon completion of the excavation. This case study focuses on the additional design revisions with their results on the inclinometer readings as the construction proceeds. 


Keywords


Deep Excavation, Retaining Wall, Secant Bored Pile, Prestressed Anchors, Shotcrete, Inclinometer Measurements

Citation


(2021). A Constructability Problem in a Deep Shoring System, Vol. 6, Issue 1, p.53-66. doi: 10.4417/IJGCH-06-01-03




DOI: http://dx.doi.org/10.4417/IJGCH-06-01-03

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