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Earthquake Analysis According to NB 35047-2015

Earthquake effects are in the stability analysis represented by horizontal and vertical forces acting at the centers of gravity of individual soil blocks. The magnitude of these forces is related to the weight of soil blocks and is calculated using horizontal and vertical earthquake coefficients. Earthquake coefficients are dependant on the position of the gravity center of each block. Therefore the coefficients have individual and different values for each one of soil blocks. Horizontal earthquake force is always oriented out form the slope massif. Vertical force can be directed upwards or downwards, the orientation is defined by the sign of the force.

Horizontal earthquake force E_hs is given by the formula:

and vertical earthquake force E_vs is determined by:

There are two types of dynamic distribution used for determining of α_i value: inverted trapezoid and polygonal. The method for setting α_i value could be seen in the Figure.

Determination of dynamic distribution coefficient αi

Height H of the range of α_i is given by points B and T. The bottom point B is the lowest point of terrain above the slip surface and the top point T is the highest point of terrain above the slip surface. G_i denotes gravity center points of individual blocks and E_ih, E_iv are horizontal and vertical earthquake forces.