Stochastic key block analysis of underground excavations

G. W. Ma, G. Y. Fu

Research output: Contribution to conferencePaper


Stochastic key block analysis is carried out for complex blocky rock mass containing non-persistent joint sets. A robust block generation program is developed to model the non-persistent discontinuities and the generated rock blocks could be of different shapes and sizes. Various uncertainties of geological and geometrical parameters of the discontinuities are considered and Monte Carlo simulations are performed. It was found that beyond a certain number of Monte Carlo realizations, the key block statistics becomes convergent. Based on the present analysis, progressive failure of a rock mass can thus be evaluated in a stochastic manner and the statistics of the key blocks including the total number and volume, the maximum and mean volume, shape and failure mechanisms etc. can be assessed. The proposed approach is applied to a hypothetical horseshoe shaped tunnel in a highly fractured rock mass. Three scenarios with varying average discontinuity size are analyzed to consider size effect on the predicted blocks and key blocks. It is shown quantitatively that a persistent discontinuity network assumption causes over-fragmentation of predicted blocks, overestimation of key blocks, and underestimation of the largest key block volume compared with non-persistent ones. More realistic representation of the discontinuities by considering the non-persistence is important to give out more reliable failure estimation of fractured rock mass.

Original languageEnglish
Number of pages10
Publication statusPublished - 1 Oct 2013
Externally publishedYes
Event11th International Conference on Analysis of Discontinuous Deformation, ICADD 2013 - Fukuoka, Japan
Duration: 27 Aug 201329 Aug 2013


Conference11th International Conference on Analysis of Discontinuous Deformation, ICADD 2013

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