PSI - Issue 10

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

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

possible preferred orientation of the grains or crystals that constitute the rock specimen. This constant generally ranges from 5 to 30 and some possible values for various rock types can be found in Marinos and Hoek (2000).

5. Methodology of the statistical possessing

The strength parameters of the two aforementioned criteria were determined statistically, for both the peak and residual strength envelopes in the case of the M-C criterion and for the peak strength envelope in the case of the H-B criterion. This task was accomplished through simple regression techniques which are implemented in RocData software (Rocscience Inc. (2017)). A range of confining pressures of 0< σ 3 <0.37 C o was used where the maximum never exceeded 35.5 MPa. In order to reduce the variability in the input data, the uniaxial compression strength was not used in the procedure, but an effort was made to conduct tests at low confining pressures wherever it was possible, due to the sudden failure of rocks that exhibit a brittle behaviour at low confining pressures.

5.1. Strength parameters of the Mohr – Coulomb failure criterion

The findings of the regression analysis for the M-C failure criterion and the range of confining pressures which were applied are summarized in Table 1.

Table 1. M-C peak and residual strength parameters along with the range of confining pressures. Rock type Rock code

Range of confining pressures (MPa)

Peak strength parameters

Residual strength parameters

φ (o)

(o)

S o (MPa)

S

φ R

oR (MPa)

Brecciated marble Brecciated marble Brecciated marble Brecciated marble

S4 SPAT S1-3 S7 PAL S1-3 S10 RAF S1-2 S22 LAV S1-2 S5 MARK S1-3 S6 MARK S1-1 S6 MARK S3-4 S6 PAIAN S1-5 S6 THOR S2-1 S6 THOR S4-1 S6 THOR S5-1 S1 MARK S1-1 S1 MARK S4-1 S1 MARK S5-1 S1 SPAT S1-1 S1 SPAT S2-4 S1 SPAT S4-1 S1 SPAT S10-1 S2 RAF S3-2 S2 THOR S5-2 S3 MARK S1-3 S3 MARK S2-6 S4 MARK S1-2

3.5-18.9 2.9-19.1 3.6-22.0 3.0-20.1 4.2-20.0 5.4-23.1 4.0-28.4 7.8-24.1 6.0-24.1 4.0-35.5 6.1-20.0 0.7-8.9 0.9-7.3 1.1-9.1 0.6-4.8 0.7-6.0 0.6-8.0 0.7-8.0 2.9-15.1 2.1-13.2 2.3-14.2 0.6-5.5 0.6-5.3

30.7 25.0 19.3 24.3 24.9 24.3 30.1 35.0 38.9 27.1 36.8

31.2 38.8 35.9 37.2 39.8 35.0 29.4 35.4 29.5 37.1 32.2 28.5 24.2 28.3 23.5 36.0 33.6 34.7 28.1 38.5 30.6 19.3 39.7

5.0 2.0 5.9 4.0 5.9 1.5 4.5 5.7 5.0 3.7 2.4 5.0 3.1 3.6 2.7 2.6 2.8 2.0 4.5 3.0 2.8 3.0 2.3

41.2 45.6 44.2 43.1 45.3 41.9 40.8 39.5 41.3 42.5 43.8 34.2 31.9 35.4 31.3 41.0 46.0 42.7 43.0 46.6 40.6 28.9 43.9

Marble Marble Marble Marble Marble Marble Marble

Porous Limestone Porous Limestone Porous Limestone

9.7 8.7 8.1 5.3 4.7 8.8 9.1

Cavernous Limestone Porous Limestone Porous Limestone Porous Limestone Micritic Limestone Micritic Limestone Compact Limestone Porous Limestone Porous Limestone

15.5 12.4 15.3

4.8 5.1