The Jefferson Memorial itself is supported on a network of 600+ concrete piles and drilled shafts that penetrate through soft Patomac River sediments and dredged material into bedrock between 80 and 138-ft below ground. However, the seawall is supported on timber pilings that are estimated to be 65 to 75-ft long, stopping short of the bedrock. The wall has been settling below the level of the adjacent plaza since about 2006 as reported by GeoPrac back in 2007. At that time Schnabel was preparing a report for the National Park Service, but I never heard anything else about it. General contractor Clark Construction Company has been working on a $12.4M repair project that includes constructing a temporary cofferdam, deconstructing the existing seawall while salvaging the historic stone facing, installing 4-ft drilled shafts into bedrock and battered concrete-filled pipe piles to support a new seawall. The project is expected to be completed in the spring of 2011. [Source: Washington Post via ASCE SmartBrief. Image: The Washington Post]
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Mizzou Memorial Union Gets Lift from TerraThane Geotechnical Foam
Univ. of Missouri’s Historic Memorial Union, Built to Honor WWI Dead, Gets New Life with TerraThane Geotechnical Foam
MOUNT AIRY, NC—The Univ. of Missouri’s iconic Memorial Union, with its Gothic architecture and central bell tower, was built to commemorate the 117 Mizzou alumni who lost their lives in WWI, and has been under silent attack. Like all buildings built atop the ancient dry riverbeds of the tributary valleys of the Missouri River, the soil beneath is a mixture of sand, clay, and fine rock particles and highly susceptible to erosion from water. So, while hundreds of thousands of students walked the hallways of the building, water escaping steam pipes far beneath caused severe drying of the soil and destabilized it enough so that erosion created voids, or cavities in the soil, some as large as four feet. In turn, this caused the concrete slab floors atop the voids to become uneven, and the eventual danger of even greater problems loomed large.
A team of engineers went after the problem, including MU alums, Matt VanderTuig, P.E., of Bartlett & West, Jefferson City, MO, and Mark Whitehead, P.E. with extensive structural design and environmental engineering management experience. They suggested to Chris Hentges, president of SIRCAL Contracting, Jefferson City, the general contractor in charge of the job, that instead of using the older method of mudjacking, a highly involved and intrusive process of drilling large holes in the slabs—sometimes removing the slabs entirely—and pumping “mud”, ultra-heavy Portland cement-based grout, into the void, then leveling the slabs, that the university might better be served by using the newer polyurethane foam system method called “foamjacking” or “polyjacking.”
[Editor] Be sure to click through for the rest of the interesting project from GeoPrac sponsor NCFI Polyurethanes and TerraThane! [/Editor]
San Francisco Millennium Tower Has Settled 16 Inches
The residential high-rise Millennium Tower in San Francisco has settled a total of 16 inches since opening, 2 inches deferentially. A spokesman for the tower owner blames the settlement on the excavation next door for the Transbay Transit Center, a $2.4 billion dollar project being constructed 60 feet underground.
However, the Transbay Joint Powers Authority (Transbay) hired geotechnical firm Arup in 2010. Their initial report indicated that the tower had already settled 10 inches by the time excavation began for the Transit center. Arup seems to have been tasked with design, installation, and perhaps monitoring of a geotechnical monitoring program, some information on the scope is available in a 2012 presentation given by Arup available on the Transbay website.
[Editor] Click through for the rest of this post. [/Editor]