Evaluation of hydrajacking tests for an unlined pressure tunnel

This paper summarizes the results and evaluation of hydraulic jacking and hydraulic fracturing tests conducted in the lower unlined pressure tunnel of the 260 m heed Mamquam hydroelectric project, located 60 km north of Vancouver, near Sqamish, B.C. Tests were conducted in the sections of low rock cover upstream of the powerhouse to establish the length of steel lining for the penstock section and in the section where the tunnel passed beneath the valley of the Mamquam River. Tests indicated the presence of a naturally enhanced stress field due to topographic effects under the valley which provided sufficient hydraulic confinement to allow elimination of the steel liner. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.