
Figure 1
Hypothetical stress–strain curves [4].

Figure 2
Relationship between modulus ratio (MR) and maximum axial strain (εa, max) using different carbonate rocks [7].

Figure 3
Main types of rock samples. (a, b) Megacryst-bearing, medium-grained, biotite monzogranites. (c) Medium-grained, biotite monzogranites with elongated monzonitic enclaves. (d) Quartz monzonite.

Figure 4
A prepared sample in the beginning of the UCS test.
Table 1
Mechanical properties of investigated Mórágy granitic rock samples.
| Rock sample | ν | E | εci | σci | εcd | σcd | εa, max | σc | MR |
|---|---|---|---|---|---|---|---|---|---|
| (-) | (GPa) | (%) | (MPa) | (%) | (MPa) | (%) | (MPa) | (-) | |
| BeR-6_U-10 | 0.24 | 74.776 | 0.030 | 50.73 | 0.091 | 152.244 | 0.278 | 181.05 | 413.0 |
| BeR-7_U-02 | 0.21 | 71.612 | 0.037 | 50.37 | 0.095 | 145.15 | 0.34 | 174.80 | 409.7 |
| BeR-7_U-04 | 0.25 | 74.447 | 0.037 | 59.61 | 0.063 | 131.70 | 0.33 | 183.39 | 405.9 |
| BeR-8_U-01 | 0.22 | 63.357 | 0.060 | 59.84 | 0.120 | 165.89 | 0.29 | 184.48 | 343.4 |
| BeR-10_U-08 | 0.21 | 66.129 | 0.025 | 30.06 | 0.044 | 77.30 | 0.22 | 137.14 | 482.2 |
| BeR-10_U-18 | 0.23 | 72.794 | 0.048 | 64.89 | 0.078 | 148.24 | 0.2 | 148.39 | 490.6 |
| BeR-10_U-20 | 0.23 | 63.787 | 0.035 | 39.28 | 0.087 | 133.75 | 0.27 | 156.74 | 407.0 |
| BeR-11_U-08 | 0.23 | 68.950 | 0.054 | 80.82 | 0.104 | 168.94 | 0.31 | 204.23 | 337.6 |
| BeR-12_U-02 | 0.22 | 79.660 | 0.029 | 34.36 | 0.08 | 128.84 | 0.18 | 133.34 | 597.4 |
| BK1-1_U-12 | 0.23 | 70.153 | 0.036 | 51.74 | 0.076 | 131.50 | 0.23 | 172.74 | 406.1 |
| BK1-3_U-01 | 0.32 | 72.891 | 0.037 | 79.97 | 0.053 | 121.05 | 0.28 | 184.59 | 394.9 |
| BK1-3_U-03 | 0.19 | 69.164 | 0.065 | 71.75 | 0.14 | 132.66 | 0.22 | 133.62 | 517.6 |
| BK1-3_U-04 | 0.18 | 71.860 | 0.045 | 47.93 | 0.113 | 112.28 | 0.18 | 153.60 | 467.8 |
| BK1-3_U-08 | 0.23 | 70.137 | 0.059 | 80.36 | 0.147 | 142.79 | 0.22 | 172.55 | 406.5 |
| BK1-3_U-12 | 0.25 | 57.425 | 0.066 | 67.99 | 0.13 | 134.11 | 0.27 | 135.14 | 424.9 |
| BK2-1_U-03 | 0.21 | 74.228 | 0.057 | 74.61 | 0.09 | 131.78 | 0.19 | 146.65 | 506.2 |
| BK2-3_U-07 | 0.28 | 77.332 | 0.036 | 59.84 | 0.068 | 119.12 | 0.19 | 143.71 | 538.1 |
| BK2-3_U-15 | 0.22 | 80.365 | 0.035 | 48.57 | 0.090 | 160.74 | 0.24 | 178.41 | 450.5 |
| BK2-3_U-18 | 0.2 | 73.819 | 0.069 | 80.22 | 0.11 | 153.84 | 0.23 | 159.16 | 463.8 |
| BK2-4_U-02 | 0.2 | 76.820 | 0.06 | 88.12 | 0.106 | 177.32 | 0.26 | 205.62 | 373.6 |
| BK2-4_U-04 | 0.21 | 77.709 | 0.045 | 60.07 | 0.090 | 130.57 | 0.20 | 155.49 | 499.8 |
| BK2-5_U-02 | 0.25 | 77.866 | 0.038 | 62.63 | 0.070 | 134.14 | 0.23 | 166.29 | 468.3 |
| Bkf-1_U-03 | 0.24 | 77.665 | 0.050 | 50.46 | 0.070 | 120.14 | 0.30 | 161.63 | 480.5 |
| Bkf-2_U-03 | 0.22 | 60.602 | 0.065 | 76.84 | 0.118 | 164.66 | 0.39 | 180.93 | 334.9 |
| Bkf-4_U-03 | 0.22 | 79.856 | 0.042 | 60.29 | 0.083 | 142.38 | 0.24 | 179.28 | 445.4 |
| Bkf-5_U-02 | 0.24 | 79.818 | 0.034 | 53.90 | 0.067 | 135.29 | 0.20 | 169.67 | 470.4 |
| Bl-112_U-02 | 0.21 | 72.897 | 0.029 | 37.88 | 0.093 | 144.19 | 0.20 | 164.59 | 442.9 |
| Bp-4_U-05 | 0.25 | 76.992 | 0.041 | 69.46 | 0.1 | 181.85 | 0.24 | 187.69 | 410.2 |
| Bp-4B_U-01 | 0.21 | 69.800 | 0.042 | 49.25 | 0.109 | 159.85 | 0.36 | 184.45 | 378.4 |
| Bp-4B_U-05 | 0.23 | 76.237 | 0.033 | 49.37 | 0.076 | 148.77 | 0.28 | 170.10 | 448.2 |
| Bp-4B_U-13 | 0.27 | 77.924 | 0.049 | 74.11 | 0.096 | 170.28 | 0.25 | 177.91 | 438.0 |
| Bp-4B_U-17 | 0.24 | 74.648 | 0.045 | 60.27 | 0.083 | 162.61 | 0.26 | 181.43 | 411.4 |
| Bp-4B_U-19 | 0.22 | 77.182 | 0.058 | 80.43 | 0.100 | 160.13 | 0.25 | 190.48 | 405.2 |
| Bp-4B_U-23 | 0.24 | 74.683 | 0.053 | 80.00 | 0.077 | 137.96 | 0.24 | 165.23 | 452.0 |
| Bp-5_U-19 | 0.25 | 73.506 | 0.031 | 49.73 | 0.056 | 121.48 | 0.23 | 149.76 | 490.8 |
| Bp-5_U-21 | 0.25 | 80.159 | 0.040 | 70.45 | 0.064 | 137,00 | 0.26 | 171.46 | 467.5 |
| Bx-81_U-03 | 0.22 | 65.782 | 0.045 | 53.44 | 0.088 | 130.84 | 0.29 | 149.28 | 440.7 |
| Bx-82_U-01 | 0.25 | 82.940 | 0.046 | 80.51 | 0.085 | 162.08 | 0.27 | 180.33 | 459.9 |
| Bx-82_U-03 | 0.29 | 84.949 | 0.024 | 49.99 | 0.044 | 120.612 | 0.2 | 166.87 | 509.1 |
| Bx-83_U-01 | 0.26 | 72.864 | 0.030 | 60.56 | 0.067 | 150.321 | 0.26 | 169.70 | 429.4 |
| Bx-83_U-03 | 0.25 | 78.072 | 0.057 | 90.36 | 0.095 | 182.085 | 0.37 | 212.42 | 367.5 |
| Bx-84_U-01 | 0.25 | 80.669 | 0.047 | 79.90 | 0.073 | 147.6 | 0.23 | 178.07 | 453.0 |
| Bx-84_U-03 | 0.27 | 81.144 | 0.039 | 69.38 | 0.062 | 138.183 | 0.26 | 166.94 | 486.1 |
| Bx-101_U-02 | 0.24 | 76.994 | 0.042 | 71.53 | 0.058 | 112.5 | 0.19 | 142.49 | 540.3 |
| Bx-101_U-04 | 0.26 | 79.300 | 0.048 | 60.58 | 0.091 | 160.96 | 0.23 | 163.19 | 485.9 |
| Bz-921_U-01 | 0.21 | 71.574 | 0.056 | 68.79 | 0.121 | 164.573 | 0.3 | 192.80 | 371.2 |
| Bz-942_U-01 | 0.23 | 73.511 | 0.053 | 73.43 | 0.11 | 182.66 | 0.28 | 198.58 | 370.2 |
| Bz-1221_U-01 | 0.2 | 69.540 | 0.049 | 58.25 | 0.100 | 165.836 | 0.29 | 213.04 | 326.4 |
| Bz-1311_U-01 | 0.3 | 88.937 | 0.035 | 75.93 | 0.060 | 163.371 | 0.23 | 206.48 | 430.7 |
| Bz-1351_U-01 | 0.25 | 67.053 | 0.034 | 50.86 | 0.080 | 145.566 | 0.28 | 159.97 | 419.2 |

Figure 5
Axial stress–volumetric strain curve with the threshold of crack initiation and crack damage and failure stress for Hungarian granitic sample (uniaxial compression case).

Figure 6
Crack volumetric strain method for crack initiation threshold determination for Hungarian granitic rock sample (uniaxial compression case).

Figure 7
Poisson’s ratio method for crack initiation threshold determination for Hungarian granitic rock sample (uniaxial compression case).

Figure 8
Observed values of modulus ratio (MR) in each of 50 examined rock samples.

Figure 9
Influence of uniaxial compressive strength (σc) on elastic modulus (E) and the value of MR for all studied samples.

Figure 10
Observed and analytical (Eq. 1) relationship between εa, max and MR.

Figure 11
Relative (ζ , %) and root-mean-square (χ) errors between calculated (Eq. 1) and observed MR.

Figure 12
Relationship between

Figure 13
Relationship between

Figure 14
Relationship between

Figure 15
Relationship between

Figure 16
Relationship between

Figure 17
Relationship between MR and crack initiation stress (σci ).

Figure 18
Relationship between MR and crack initiation strain (εci).

Figure 19
Relationship between

Figure 20
Relationship between

Figure 21
Relationship between