Microtunneling in Soft Soils, Louisiana

A 72-inch diameter, 700-foot long microtunnel installation was successfully completed in early 2022, providing private, pressurized, utility conveyance under a combination Union Pacific Railroad and Burlington Northern Santa Fe rail yard. A total of 14 active railroad tracks, a rail yard, and a Louisiana Department of Transportation Highway were crossed with the tunnel installation. Ground conditions at the site consisted of 65 feet of very soft to soft clays, unerlain by a pressurized sand aquifer. Microtunnel construction was successfullly completed despite challenging subsurface conditions including soft, plastic clays difficult to process and steer the microtunnel machine through and driven wooden piles encountered periodically during tunneling.