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.
The
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.
