Microtunneling MARTA

by Tom Iseley, (M.ASCE), Dir.; Trenchless Technology Center, Louisiana State Univ., Ruston, LA,


Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 12, Pg. 50-53


Document Type: Feature article

Abstract: Microtunneling technology was used to provide temporary support for two transit tunnels that were part of the extension of the Metropolitan Atlanta Rapid Transit Authority system. This is the first application of the technology for a major tunnel. The MARTA extension crossed the busiest area interstate. Because of the potential for traffic disruption, a tunnel was considered the only way to proceed. The tunnel crowns were extremely close to the highway, with as little cover as 5 ft. The solution was to drive a steel pipe arch to provide ground support during tunnel construction. Horizontal jet grouting was a further support before excavation. The agency evaluated five methods of tunnel construction before selecting the microtunneling; advantages of each are described. A smaller project, a golf course tunnel, is another recent microtunneling project. This project also had minimal ground cover between the tunnel crown and a very busy highway close to the crown. Trenchless technology is a broader term for microtunneling, and includes installing larger diameter pipe with minimal surface disruption. There have been many recent applications in the civil engineering field.

Subject Headings: Arches | Construction | Microtunneling | Steel pipes | Support structures | Tunneling | Tunnels

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