Evaluation of hydrajacking tests for an unlined pressure tunnel

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