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Abstract
The mechanical behavior of jointed rock masses is determined by the properties of the
rock matrix, geometry and properties of discontinuities. Joints and other geologic
structures often increase significantly the deformability, and reduce the strength of the
systems. The main problem with natural slopes, that its failure is unpredictable. The
study of discontinuities in rock slopes is a very important factor for its stability and
also for the safety of near habitants. Mokattam plateau slopes in Egypt are an example
for hazard rock slopes surrounded by high population densities. Presence of
intercalated shale layer in the Mokattam slopes causes a lot of instability problems due
to shale softening and degradation when subjected to humidity or leakage resulting in
many fatal accidents in the last years due to rock fall on humans and buildings. Most
of the last stability researches use continuum or empirical approaches (ex; finite
element programs). This approach is acceptable in the case of heavily jointed rock
masses. But in reality, the rock mass is controlled by movement of joint-bounded
blocks and/or intact rocks deformation, simulation of large displacements and large
rotations is difficult with this method. Numerical modeling of jointed rock slopes
using discontinuum distinct element techniques has proved to be the most reliable
technique in these analyses.
The main objective of the present thesis is to investigate the behavior and stability of
jointed rock slopes using discontinuum distinct element code (UDEC). This was
conducted by designing and programming an analyzed model to analyze the stability
of this complicated rock slopes. The designed model was applied on the Mokattam
upper plateau slope and the model results were compared with the available field
displacement readings to ensure the accuracy of the designed model in addition with
taking into account the softening of shale layer on five steps. The developed model
results agree well with the field results. Accordingly, an extensive parametric study
was carried out to determine the effect of five important joint properties on the
stability of rock slopes (which are joint shear stiffness, joint normal stiffness, joint
friction, joint cohesion and joint tension) also, the effect of shale layer properties and
its inclination. Design and guideline values were represented for these parameters
which will benefit researchers in their future studies and analyses. Also, an economic
mean of protection was suggested to protect the population surrounding the upper
Mokattam plateau slopes by determining the safe catchment length below these slopes
using another developed analysis model which simulate a practical rock fall for one of
these slopes. Accordingly, the actual evacuation areas could be determined and
implemented by state institutions.
Finally, this research project has helped to identify the jointed rock slopes behaviour
and its associated problems in the Mokattam area and to increase the sensitivity of the
proposed measures, which can help in mitigating the slope failure reasons and to
achieve security of the population.