PSI - Issue 10

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

117

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

140

140

σ 1 = 4.2σ 3 +65 r 2 =0.99

5 th imminent failure point

Peak strength

120

120

4 th imminent failure point

Residual strength

100

100

80

80

3 nd imminent failure point

Residual strength data Peak strength data

60

σ 1 (MPa)

60

σ 1 =5.2 σ 3 +12.8 r 2 =0.98

Unloading

40

AXIAL STRESS (MPa)

40

2 nd imminent failure point

20

20

1 st imminent failure point

0

0

0

500

1000 1500 2000 2500 3000

0

5

10

15

20

σ 3 (MPa)

AXIAL DISPLACEMENT ( μ m)

a (b) Fig. 3. (a) Axial stress-axial displacement curve and (b) peak and residual strength data along with their M-C fit lines of a sandstone sample (S15 PAL S1-2). b (a)

5.2. Strength parameters of the Hoek – Brown failure criterion

The results of the adjustment of the H-B criterion on the peak triaxial test data, i.e. the constant m i and the back calculated uniaxial compressive strength C 0 , and the range of confining pressures which were applied are summarized in Table 2.

Table 2. H-B peak strength parameters along with the range of confining pressures. Rock type Rock code

Range of confining pressures (MPa)

Peak strength parameters C 0 (MPa) m i

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

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

106.9

5.4 9.6 9.6 8.7 8.3 5.1 7.6 4.8 5.7 4.7 3.5 5.1 3.5 9.7 6.7 7.3

99.4 67.4 93.5 99.7 86.4

Marble Marble Marble Marble Marble Marble Marble

10.5

100.0 129.4 130.6

92.5

11.5

130.3

Porous Limestone Porous Limestone Porous Limestone Porous Limestone Porous Limestone Porous Limestone Cavernous Limestone

31.9 26.5 25.6 15.6 16.5 31.8 33.5