Table 1 Characteristics of different sample groups.
Group | No. | Â \(\sigma_{2}\) / MPa | Â \(\sigma_{3}\) / MPa | Note | |
|---|---|---|---|---|---|
Borehole arrangement pattern | Borehole spacing/mm | ||||
Single hole | C1 | 20 | 15 | All samples have center-positioned through holes, same below | |
Double hole | Z2-15 | 20 | 15 | Vertical | 15 |
Z2-25 | 20 | 15 | Vertical | 25 | |
Z2-35 | 20 | 15 | Vertical | 35 | |
X2-15 | 20 | 15 | Diagonal | 15 | |
X2-25 | 20 | 15 | Diagonal | 25 | |
X2-35 | 20 | 15 | Diagonal | 35 | |
Triple hole | Z3-15 | 20 | 15 | Vertical | 15 |
Z3-25 | 20 | 15 | Vertical | 25 | |
Z3-35 | 20 | 15 | Vertical | 35 | |
X3-15 | 20 | 15 | Diagonal | 15 | |
X3-25 | 20 | 15 | Diagonal | 25 | |
X3-35 | 20 | 15 | Diagonal | 35 | |
Intact rock | WZ-20 | 20 | 15 | / | |
