Research Article
Collapsed Shape of Shallow Unlined Tunnels Based on Functional Catastrophe Theory
Table 4
PFC parameters of the surrounding rock after calibration.
| | Name | Notation | Value |
| | Ball density | (kg/m3) | 2940 | | Porosity | | 0.15 | | Ball minimum radius | (m) | 0.05 | | Ratio of maximum to minimum radius | | 1.5 | | Normal contact stiffness of the ball | (Pa) | 5.6 × 108 | | Contact stiffness ratio of the ball | | 10 | | Ball-ball contact modulus | (Pa) | 5 × 109 | | Ball friction coefficient | | 0.5 | | Normal strength of the contact bond | (Pa) | 2 × 104 | | Contact-bond strength ratio | / | 1 |
|
|
