recent advances in large diameter diaphragm wall shafts

Maximum hoop force is at 23m depth and is equal to 12.5MN.Using Hain model (2D non-linear approach), buckling force is approximately equal to 95EI/R 2 =75MN.Factor of safety on buckling is larger than 6.Inscribed annulus thickness without deviation is equal to 1.158m.Maximum deviation at 23m depth = 10.5cm.Inscribed annulus thickness with +/-10.5cm deviation is equal to 0.948m.Hoop stress at 23m depth without deviations is equal to 10.8MPa.Hoop stress at 23m depth with +/-10.5cm deviations is equal to 13.2MPa.Figure 7. Example Project Information, Excavated Shaft Photo, and Idealized Cross-SectionList of example large diameter and deepshaftsA partial list of recent large diameter shaftsconstructed worldwide is summarized in Table 1.SummaryThis paper provided an overview of recentadvances in the design and construction ofcircular diaphragm wall systems. Thesesystems are especially attractive for the EPAmandated combined sewer overflow containersbecause they can be constructed to retain largefluid volumes without any internal or externalsupport. Moreover, the systems are costeffective and provide higher certainty ofexecution during construction relative tocompeting systems such as sunken caissons.Additionally, elliptical and circular arc segmentscan also be used to construct efficient systemswith different shapes. The incorporation of thearc segments allows for thinner walls, lightersteel reinforcement and minimal internal orexternal support.ReferencesHain, H. H. (1968). Zur Stabilitat ElastischGebetteter Kreisringe Und Kreiszylinderschalen,University of Hannover, Mitteilung Nr. 12.Timoshenko, S. and Gere, J. (1961) Theory ofElastic Stability, McGraw Hill, New York, 2 ndEdition.