Some Landmark Projects DMM suddenly came to the fore in the U.S. in 1987 when the Geo-Con-led alliance with SMW Seiko commenced the seismic retrofit of the foundation of Jackson Lake, Wyo. The DMM alternate was used principally to create an interlocking “honeycomb” of soilcrete columns, as well as a seepage cut-off. This project involved over 400,000 linear ft (120,000 linear m) of columns and was widely and justifiably publicized in the technical press. Following a period when DMM was principally used for environmental applications and increasingly for small earth retention projects (when suitably reinforced a n d a n c h o r e d o r braced), the Nicholson- Seiko JV used the technique to provide (37,200 m ) of earth support walls at the Ted Wi l l i ams Tu n n e l Approach in Boston, Mas s . The indus t ry learned much about the construction of DMM in glaciated terrains, and about the durability of such walls in freeze- thaw conditions. Confidence in the technique remained at a high level in the Boston Central Artery Project, culminating in the second major DMM project in the about 380,000 sf 2 cu yds (420,000 m ) of soil were treated by a major JV including Nicholson and SMW Seiko during the construction of the Fort Point Channel contract and adjacent structures. One estimate has it that, by 1998, more than 20 excavation support walls had been built with DMM in the U.S., including three involving the “gravity wall” concept, without anchors or braces. These projects included walls for the Cypress Freeway Replacement Project, Calif.; the Islais Creek Sewerage Scheme, Ga.; the Marin Tower, Hawaii; the Lake Parkway, Wis.; and the LA Metro, Calif. By the late 1990s, the number of competitors grew, with systems being offered by well- established U.S. contractors such as Hayward Baker, Schnabel, Malcolm and city in the late 1990s when about 550,000 3 54 • DEEP FOUNDATIONS • NOV/DEC 2013 Other notable transportation-related projects of the period included Stabilator’s dry DMM projects at I-15 Utah, (1997) and in San Francisco, Calif. (1998), Raito’s wet DMM project at Woodrow Wilson Bridge, cu yds (275,000 m ) of dry, shallow mixing at Jewfish Creek, Fla., in 2005-2006. Geo-Con had built a DMM cut-off wall Va. (2000), and Hayward Baker’s 350,000 3 through Lockington Dam, Ohio, and similar dam/levee cut-offs were installed in the early 1990s by Seiko and Raito, at projects such as Cushman Dam, Wash.; Lewiston, Idaho and Sacramento, Calif. However, the main application for DMM on hydraulic structures has been for seismic retrofit, and from the early 2000s onwards, major DMM installations had been recorded at Sunset North Basin Dam, Condon Johnson; Japanese contractors such as Raito, Fudo, Tenox and Jafec; and European-owned U.S. subsidiaries such as Treviicos, Underpinning and Foundation Skanska, Soletanche and Bauer; as well as a number of primarily environmental remediation contractors, frequently the off- shoot of the original Geo-Con company. Calif.; Clemson Upper and Lower Diversion Dams, S.C.; and San Pablo Dam, Calif., all by Raito. A landmark, full-scale test of various DMM (and other) techniques was conducted in 2006 by Treviicos at Tuttle Creek Dam, Kan., although the subsequent production works employed a slurry wall method. The New Orleans District of the U.S. Army Corps of Engineers (USACE) had, in 2001, the foresight to organize and fund a full-scale demonstration of (dry) DMM in its soft cohesive, organic soils. This field test, with input from specialists in the U.S., Japan and Sweden, was a fasci- nating technical success: DMM could be made to work in the putty-like soils of the Mississippi Delta. However, DMM as a routine technique for solving foundation problems in the region was judged to be either (or both) too “radical” or too costly (depending on one’s viewpoint), and so the idea was politely shelved. Then, in August of 2005, the historic Crescent City was impacted by Hurricanes Katrina and Rita, and traditional paradigms were overturned in the face of necessity and expediency. Task Force Guardian was formed by the USACE and, by early 2006, DMM work, both wet and dry, was conducted on an emergency basis on four projects involving gate construction and levee remediation. In the following 4 years, 6 more projects were done under somewhat more relaxed conditions by the same two contractors — Hayward Baker (dry) and Raito (wet). These relatively modestly-sized projects were the forerunners for the massive LPV 111 project, an 8.8 km (5.5 mi) long component of the Lake Pontchartrain and (1.7 million yd ) of wet DMM, to improve This project involved over 1.3 million m 3 (1.1 million yd ) of dry levee fill. The DMM was conducted principally by Treviicos (wi th cont r ibut ions f rom Fudo placement of over 0.8 million m 3 the soft foundation soils, prior to the 3 Vicinity Hurricane Protection Scheme. 3
