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Rock Stability 

GEO5

Geotechnical software

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Earthquake effect

The program allows for computing the earthquake effects with the help of two variables – factor of horizontal acceleration Kh or the coefficient of vertical earthquake Kv.

Coefficient of vertical earthquake Kv

The coefficient of vertical earthquake either decreases (Kv > 0) or increases (Kv < 0) the unit weight of a soil, water in a soil and material surcharge by multiplying the respective values by 1-Kv. It is worth to note that the coefficient Kv may receive both positive and negative value and in case of sufficiently large coefficient of horizontal acceleration the slope relieve (Kv > 0) is more unfavorable than the surcharge.

Factor of horizontal acceleration Kh

In a general case the computation is carried out assuming a zero value of the factor Kh. This constant, however, can be exploited to simulate the effect of earthquake by setting a non-zero value.  This value represents a ratio between horizontal and gravity accelerations. Increasing the factor Kh results in a corresponding decrease of the factor of safety FS.

The coefficient of horizontal acceleration introduces into the analysis an additional horizontal force acting in the center of gravity of a respective  block with the magnitude Kh*Wi, where Wi is the block overall weight including the material component of the slope surcharge.

The following table lists the values of the factor Kh that correspond to different degrees of earthquake based on M-C-S scale.

M-C-S degree 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

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