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SHEET PILE RETAINING WALL - Design Considering Wall Displacments?[Subject Prev][Subject Next][Thread Prev][Thread Next]
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- Subject: SHEET PILE RETAINING WALL - Design Considering Wall Displacments?
- From: "Polhemus, William" <wpolhemus(--nospam--at)craworld.com>
- Date: Tue, 10 Feb 2015 19:33:23 +0000
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I seem to have run into a mental ditch, and can't get out. Maybe it's my age. Anyway, please consider this along with me. I've got a 20-ft deep underground vault, about 30 ft by 40 ft in plan, open at the top, formed by driving sheet piles in a box shape. After excavation, a 2-ft min. thick slab will be poured at the bottom to seal the vault off from groundwater. There is estimated to be about a 16-ft hydrostatic head causing pressure at the bottom of the slab, which must be resisted. I've computed the necessity of having shoring (waler) frames at about 3 feet and 16 feet from the top of the vault respectively. After the seal slab is poured, the lower waler frame could be removed (I'd use something like a hydraulically-operated shoring system for the lower waler in that case). The typical design examples I see in textbooks, and the sheet pile design software I am using, do not seem to take into account the changing deflected shape of the sheet pile during construction. For instance, it will always set the deflection value at the shoring points at ZERO deflection, even though at the time of the shoring installation, the deflected position of the point at which the shoring is placed may be quite significant. I realize this can be considered relative deflection, but I cannot tell if the REACTIONS that it's giving me for the shoring take this into account. And even more to the point, if I shore everything, then place the seal slab, the program then considers the seal slab as a "shore point," and gives me a value for the compressive force per unit length along the edge of the slab. If I use this force to compute the resistance of the slab against hydrostatic uplift (assuming a coefficient of friction between the concrete and the steel of the sheet pile, established by the Florida DOT design manual - which seems to have become a sort of de facto standard for this purpose), the slab works to resist the uplift. But I don't think that force is really there. Unless I remove the lower shore, and allow the sheet to deflect and "clamp" the slab, the actual "shoring force" at the slab appears to me to be ZERO. What am I missing here? _____________________________________________ CRA and GHD have merged! To learn more, visit www.CRAworld.com/ghd ------------------------------------------------------------------------- Post your message to the list by sending it to: SEAINT-SEAOSC(--nospam--at)mail-list.com. The email messages sent to the list will be saved in an archive on the World Wide Web. These archives are located at: http://archive.mail-list.com/SEAINT-SEAOSC To contact the list owner, send your message to: SEAINT-SEAOSC-list-owner(--nospam--at)mail-list.com. Sponsored By: Pacific Structural & Forensic Engineers Group, Inc. (PSFEG) To unsubscribe, switch to/from digest, get on/off vacation, or change your email address, click here. <http://cgi.mail-list.com/u?ln=seaint-seaosc&nm=seaintma%40euken.net>
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