Analytical evaluation of post-excavation hydraulic conductivity field around a tunnel

Changes in the hydraulic conductivity field around a tunnel that accompany underground excavation are difficult to characterize due to the nature of hydromechanical coupling processes in fractured rock masses. A methodology is developed to represent changes in the post.excavation hydraulic conductivity as a result of excavation-induced strains. Relationships linking changes in hydraulic conductivity and excavationinduced strain are defined through the assumption of an equivalent porous medium. Analytical solutions for the post.excavation hydraulic conductivity field are obtained by applying these relations to fractured rock surrounding a circular tunnel. The analytical solutions are then used to develop a dimensionless chart which defines the relationship between normalized ratios of post.excavation to pre.excavation hydraulic conductivities and the dimensionless radium. This chart is verified against field results from Buffer Mass Test at the Stripa.