The program analyses the
behaviour of the rock slopes under seismic conditions. It
evaluates the displacements of a rock block subject to dynamic
forces, on the basis of a given accelerogram.
The use of a calculation
method based on a given accelerogram for rock slope stability
analysis allows one to take into account the duration and the
intensity of the accelerogram itself (this not being the case
with the normally used limit equilibrium methods).
This allows a more realistic estimation of the effects of a
seismic event on a potentially unstable rock block.
The program requires the shape of the rock slope face, the
geomechanical parameters of the rock mass, the shape of the
sliding surface and, as an option, of the water table.
In order to create a synthetic accelerogram, one should define
the duration and maximum value of the foreseen seismic
acceleration, the number of waves and their characteristic
period. A recorded real accelerogram can also be used.
synthesis of the accelerogram is carried out in four stages:
selection of the wave characteristic period range; subdivision
of this range into a number of intervals; generation of the
sinusoidal waves with a phase obtained through random number
generation; summation of the generated waves and determination
of the acceleration values that make up the accelerogram.
The acceleration value
that brings the slope to a limit equilibrium condition is
calculated with a pseudostatic analysis; this acceleration is
assumed to be the acceleration threshold beyond which velocity
and relative displacements are generated.
When the duration of the event and the maximum acceleration is
known, the program determines, through numerical integration of
the accelerogram values, the velocities and displacements in the
direction of the planar sliding surface.
The summation of the
displacements calculated each time the accelerogram exceeds the
critical acceleration determines the total displacement at the
end of the seismic event. This constitutes a fundamental
parameter with which the stability of the slope can be judged.
The same parameter set allows the program to generate different
accelerograms, each of which can be used to calculate different
final displacements of the potentially unstable blocks for
further statistical analyses.