A public transportation agency encountered water infiltration into the subway system, due to voids behind the cross-passage section of the tunnel.
Working within the cross-passage segment of the tunnel, 15 investigative holes were drilled to identify the location of the voids which contained water. Mechanical packers with ball valve assembly were then installed into the drilled holes where the presence of water inflow was observed. Cement grout was continuously injected into the drilled holes via the mechanical packers until grout was detected resurfacing from an adjacent open valve. The resurfacing of grout indicated that the cavity had been filled, as the water had been displaced away from the cross-passage section.
Cement grout injection using microfine cement, mechanical packers and a cement grout pump were used to fill the voids behind the cross-passage section. The method eliminated the infiltration of water into the tunnel and allowed utility contractors to work safely within the cross-passage.
