Influence of Seismic Effects
The programs takes into account the earthquake effects using two variables - factor of horizontal acceleration Kh and factor of vertical acceleration Kv.
The factor of acceleration is a dimensionless number, which represents the seismic acceleration as a fraction of the gravity acceleration. Earthquake effects are introduced through the seismic force S, which is determined by multiplying the weight of the rock subjected to the earthquake (i.e. rock block) by the factor of acceleration. When assuming seismic effects only in the horizontal direction the seismic force is given by:
where: | Kh | - | factor of the horizontal acceleration |
W | - | weight of the rock body |
The seismic force always acts in the center of gravity of the rock body. Usually, only seismic effects in the horizontal direction are considered. Nevertheless, the program also allows for treating the vertical direction (with the help of vertical factor of acceleration Kv). The effects in both directions are then combined.
M_C_S grade | Horizontal acceleration | Factor of horizontal acceleration |
((MSK-64) | [mm/s2] | Kh |
1 | 0.0 - 2.5 | 0.0 - 0.00025 |
2 | 2.5 - 5.0 | 0.00025 - 0.0005 |
3 | 5.0 - 10.0 | 0.0005 - 0.001 |
4 | 10.0 - 25.0 | 0.001 - 0.0025 |
5 | 25.0 -50.0 | 0.0025 - 0.005 |
6 | 50.0 - 100.0 | 0.005 - 0.01 |
7 | 100.0 - 250.0 | 0.01 - 0.025 |
8 | 250.0 - 500.0 | 0.025 - 0.05 |
9 | 500.0 -1000.0 | 0.05 -0.1 |
10 | 1000.0 -2500.0 | 0.1 -0.25 |
11 | 2500.0 -5000.0 | 0.25 -0.5 |
12 | > 5000.0 | > 0.5 |
The values of factor Kh correspond to individual degrees of earthquake according to M-C-S scale