PSI - Issue 10

D. Kotsanis et al. / Procedia Structural Integrity 10 (2018) 112–119

119

D. Kotsanis et al. / Structural Integrity Procedia 00 (2018) 000 – 000

As it was stated before, the m i constant is a characteristic of the intact specimen and although the suggestions of the above researchers are based on a large amount of data, it is not possible to include all the possible inherent variabilities of the geological materials, especially in the case of sandstones and porous limestones. It is worthwhile to notice at this point that many researchers in the past have given a wider range of results, such as Sabatakakis et al. (2017) and references there in. Especially in the case of Neogene sandstones from selected locations from Greece, Sabatakakis et al. (2017) have given a m i range with lower bounds similar to those found in this work. 6. Discussion Thirty one intact rock specimens comprising three petrological types from selected sites in the East Attica Prefecture of Greece were prepared and tested under a multi - stage triaxial test procedure. Two failure criteria were used in order to model the response of the peak and the residual strength data to the variation of the confining pressure. Both models fitted well with the experimental data, although the H-B criterion due to its non – linear formulation seems to be more adequate for the selected range of the confining pressure and the rock types used. In the residual state of strength and according to the M-C criterion fits, the cohesion was decreased dramatically and the angle of internal friction was increased, due to the continuous disaggregation of the specimen. In case where the peak strength of the intact rock is attained, the residual strength in conjunction with the mechanical properties of the rock joints, determines the response of the rock mass to the surrounding environment. Nowadays, efforts are being made to demonstrate the importance and applicability of the residual strength parameters in many practical aspects such as rock stability problems (Tiwari and Latha (2017)) and underground excavations (Cai et al. (2007)). The derived strength parameters are in accordance with the results given by other researchers. The results of our work can serve as a contribution to the existing results found in the literature, as well as, an input to the construction of a geotechnical database for the study area.

Acknowledgements

The experimental data and statistical interpretation presented in this work are part of the PhD thesis of the first of the authors. Further, we would like to thank Mr. S. Kotsanis for his contribution to the field work, Dr. G. Papanto nopoulos and Mr. Zurda Ertol for their contribution in the experimental procedure.

References

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