Quantitative assessment of depth and extent of notch brittle failure in deep tunneling using inferential statistical analysis

Kang Hyun Lee, In Mo Lee, Young Jin Shin

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


A stress-induced brittle failure in deep tunneling generates spalling and slabbing, eventually causing a v-shaped notch formation. An empirical relationship for the depth of the notch to the maximum tangential stress assuming an equivalent circular cross-section was proposed (Martin et al. 1999). While this empirical approach has been well recognized in the industry and used as a design guideline in many projects, its applicability to a non-circular opening is worth revisiting due to the use of equivalent circular profile. Moreover, even though the extent of the notch also contributes to notch failure, it has not been estimated to date. When the estimate of both the depth and the extent of notch are combined, a practical and economically justifiable support design can be achieved. In this study, a new methodology to assess the depth as well as the extent of notch failure is developed. Field data and numerical simulations using the Cohesion Weakening Frictional Strengthening (CWFS) model were collected and correlated with the three most commonly accepted failure criteria (σ13, Dismaxc, σdevcm). For the numerical analyses, the D-shaped tunnel was used since most civil tunnels are built to this profile. Inferential statistical analysis is applied to predict the failure range with a 95% confidence level. Considering its accuracy and simplicity, the new correlation can be used as an enhanced version of failure assessment.

Original languageEnglish
Pages (from-to)201-206
Number of pages6
JournalGeomechanics and Engineering
Issue number2
Publication statusPublished - 2020 Apr 25

Bibliographical note

Publisher Copyright:
© 2020 Techno-Press, Ltd.


  • Brittle failure
  • Deep tunneling
  • Inferential statistical analysis
  • Spalling

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Geotechnical Engineering and Engineering Geology


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