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

J. Liu, D. Elsworth, B. H. Brady

Research output: Contribution to journalConference articlepeer-review

5 Scopus citations

Abstract

Changes in hydraulic conductivity field around a tunnel that accompany the 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 excavation-induced strain are defined through the assumption of an equivalent porous medium. These relationships may be used to represent a whole spectra of fractured rock masses by assigning different Rm (modulus reduction ratio) values. When the modulus reduction ratio, Rm = 1, the rock mass and intact rock material moduli are identical, and the strain is uniformly distributed between fractures and matrix. This results in the smallest possible change in conductivity. When Rm = 0, the strain is applied entirely to the fracture system and precipitates the largest possible change in conductivity. These values bound the possible ranges in behavior of the system in a natural and mechanistically defensible manner. Analytical solutions of post-excavation hydraulic conductivity field are obtained by applying these relations to fractured rock masses around 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.

Original languageEnglish (US)
Pages (from-to)566
Number of pages1
JournalInternational journal of rock mechanics and mining sciences & geomechanics abstracts
Volume34
Issue number3-4
DOIs
StatePublished - Apr 1997
EventProceedings of the 1997 36th US Rock Mechanics ISRM International Symposium - New York, NY, USA
Duration: Jun 29 1997Jul 2 1997

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology
  • Engineering(all)

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