Rail Crossing Casing Annular Grouting — Douro Street, Toronto

The problem. A 1,200 mm steel casing approximately 50 metres long had been installed beneath the rail corridor at Douro Street in Toronto, carrying thirty 4-inch FRE utility ducts. The annular space between the ducts and the casing — an estimated 45 cubic metres — had to be completely filled with a high-flow lightweight grout, and groundwater infiltrating the launch shaft had to be removed from the shaft and casing before any grout could be placed.

The repair. The ducts were installed on custom-fabricated pipe spacers to hold their position during grouting. After a vactor truck dewatered the shaft, the crew pumped lightweight grout into the casing from the injection end at an average pressure of just 20 psi (1.3 bar) — low enough to protect the ducts — with a vent pipe at the receiving shaft confirming progress. Work was staged around winter weather: 10 cubic metres placed on day one, 30 on day two after re-dewatering, and a final 6 to finish.

The result. 46 cubic metres of grout were placed against the 45 cubic metre theoretical volume, grout was observed exiting the vent pipe at the receiving shaft — the confirmation that the annulus was full — and all thirty FRE ducts were proven free and clear on completion. (Project reference #70-15-11-2434.)

Project photos