Emergency Repair to Prevent a Major Sinkhole Utilizing Trenchless Methods

摘要

The Wellesley Street Emergency Repair was completed on a 900 mm (36inch) x 600 mm (24inch) brick sewer under a very busy street in the heart of downtown Toronto, ON. The sewer was programed for CIPP rehabilitation by Toronto Water, but pre-lining videos revealed both extensive debris and serious instabilities in the brick sewer (the obvert of the pipe exhibited deformation with reverse curvature). As the debris was carefully removed, a large hole in the pipe was discovered and an even larger void outside the pipe revealed itself. An active service connection opposite the void increased the risk of the void size increasing rapidly. The void was determined to be approximately 4 m long and 6 m3 (8 yds3) in volume. To further increase the severity of the risk of the void propagating to the surface, a 12-inch cast iron watermain was within 1 m of the top of the void.The logistics to repair the pipe by excavation would be disruptive, complex, and inherently of high risk due to the presence of the watermain. The ultimate solution was a very innovative trenchless fix which included installing a CIPP liner to stabilize the pipe and then using an ACI 229 controlled density fill to fill and stabilize the void through a small 150 mm (6-inch) hydro-vacuumed hole in the pavement.This paper will focus on the technologies utilized to quantify the risk, the decision process to determine the best solution, and details on the design implementation of the emergency repair.