Wet soil mix circular shaft in Tampa, FL

Wet soil mix circular shaft with plug in Hillsbororough River, Tampa, Florida, USA

Project designed and constructed by Hayward Baker with our DeepEX software

The site is just west of downtown Tampa, on the Hillsborough River. A new 48” diameter water main is to be installed by micro-tunneling under the river. On the west bank, there are alternating layers of sand, cherty limestone, and clay. Hayward Baker used DeepEx to design a combination earth retention and bottom plug system for the tunnel launch shaft that required excavating ~37-ft deep. The system was comprised of overlapping 6.5-ft diameter wet soil mix columns in a compression ring around the perimeter (unreinforced), and through a 6 to 8 ft thick targeted zone inside the ring (for the bottom plug).

DeepEX considers both installation tolerances and overalps to perform checks for the unreinforced soil mix section. The DeepEX stress checks consider both the tensile and compressive strength of the mix.

The mixing and excavation were successful. No dewatering was required. The tunneling has been completed.

Please contact Tanner Blackburn, Ph.D., P.E. at for more details (e-mail: jtblackburn@haywardbaker.com).