Milwaukee, Wisconsin
February, 2001
A tunneling contractor excavating a 1.2 meter diameter tunnel in soft ground in Milwaukee, U.S.A. encountered a collapse associated with heavy inflows of water. Several hundred cubic meters of sand and gravel were washed into the tunnel.
ECO designed and directed the installation of a grouting program to recover and advance the tunnel.
The debris inside the tunnel and in front of the face was first stabilized, enabling a temporary bulkhead to be constructed. Hot bitumen and regular cement based grout were injected behind the bulkhead into the soil in the area of the collapse. This stabilized the soil and prevented further washouts from occurring.
The tunnel was completed with no further delays following the grouting operation.