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crete was placed in three lifts per wall. The first schedule and on budget with 18% cost savings to layer of shotcrete was placed encapsulating the the owner. Such design has showcased the effec- first layer of mesh and left enough of the lattice tive and fast use of shotcrete as means for reha- girder exposed such that the second layer could bilitation and repair works in existing tunnels that be installed. The second placement encapsulated only allow limited time for tunnel closures. all of the steel and was left rough so that a monolithic finish coat could be applied last to References provide aesthetic appeal. The final layer was FHWA-NHI-09-010, 2009, “Technical Manual for Design finished with a broom and was sprayed with a and Construction of Road Tunnels —Civil Element,” Federal curing compound to attain proper cure and avoid Highway Administration, Washington, DC, 704 pp.ACI Committee 318, 2005, “Building Code Requirements surface cracking. for Structural Concrete (ACI 318-05) and Commentary,” American Concrete Institute, Farmington Hills, MI, 430 pp. Conclusions For the Liberty Tunnel rehabilitation project, time was of the essence due to a short and limited closure of the tunnel. The alternative design of Axel G. Nitschke received his the self-bearing shotcrete ventilation arch wall MSc and PhD in civil engi- provided the contractor greater flexibility and neering in 1993 and 1998, reduced construction risk during the ventilation respectively, from Ruhr Uni- arch wall installation. versity Bochum, Bochum, Ger- The simplicity in the design and the easy and many, and is a licensed pro- quick installation of the shotcrete arch wall fessional engineer in Virginia system allowed the project to be completed on and California. He has gained time and within budget. The tunnel was even more than 20 years of in-depth, on-the-job expe- completed 2 days earlier than the proposed rience in all aspects of underground construc- tion, geotechnical engineering, and mining. He has worked on the engineering and construction Honorable Mention of a large number of tunnel projects in Europe, the United States, Canada, and Colombia. He is Project Name well-experienced in all ground conditions, rang- Liberty Tunnel Arch Restoration ing from soft ground to hard rock, and the asso- ciated implications for design and construction Project Location methods. Nitschke has held key positions such as Pittsburgh, PA Senior NATM Engineer, Contract/Claims Man- Shotcrete Contractor ager, Risk Manager, Design Manager, and Proj- Coastal Gunite Construction Company* ect Manager. General Contractor Swank Construction Company, LLC John Becker is an ACI Cert- ified Nozzleman who, for the Architect/Engineer last 5 years, has worked in Gall Zeidler Consultants many capacities—most recently Project Consultant/Inspection as Project Manager—for Coas- Hill International Inc. tal Gunite Construction Com- Material Supplier/Manufacturer pany, based in Cambridge, MD. In addition to the Fort The QUIKRETE Companies* McHenry Tunnel, he has been involved with Project Owner many shotcrete projects large and small, includ- Pennsylvania Department of Transportation ing the $15 million Bonner Bridge Rehabilita- *Corporate Member of the tion Project in Nags Head, NC, and the $5 mil- American Shotcrete Association lion Old Mill Creek Sewer Rehabilitation Project in St. Louis, MO. 2015 ASA Outstanding Shotcrete Project Awards Program Now Open! Submission deadline: Thursday, October 1, 2015 | 5 pm EST Visit www.shotcrete.org/ASAOutstandingProjects Shotcrete • Winter 2015 49


2015WinterShotcreteEMag
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