Analysis of Slopes Stability

This technical-scientific report describes the methods used and results obtained for an evaluation of the conditions of hydrogeological instability affecting the archaeological area of Khinis (Iraqi Kurdistan), which constitute a danger for safeguarding and protecting the local cultural heritage and its fruition by visitors.

Land surveys have enabled us to understand the geological structure of the territory and gather the information necessary for the determination of the gravitational instability processes acting on some rock walls, including those on the surface of which bas-reliefs dating to700 BC have been sculpted.
By means of analysis of the fractured, discontinuous-type rock bodies, focused on evaluating the characteristics of the discontinuity systems that pass through the local geological sequence, it was possible to construct geometric and dynamic models of the stability conditions of some discrete rock volumes (i.e. isolated by the discontinuities). With the aid of aerial photogrammetric surveys, the dimensions and volumes of these elements were calculated and the potential type of kinematic failure mechanism was defined. Lastly, the results of the stability analyses permitted an evaluation of the equilibrium conditions between the active forces and the resistant forces (the limiting equilibrium) and to propose some measures that may be taken so as to mitigate the risk of collapse. The stability conditions are also discussed in relation to factors that might potentially trigger collapses, such as seismic vibration and rainwater infiltration.

In addition, an analysis was conducted of processes of rock fall from the rock faces present on the upper part of the Khinis slope – above the series of bas-reliefs, which are close to the valley floor. Using probabilistic and kinematic 3D modelling of the propagation trajectories obtained with ROTOMAP® software produced by GeoSoft International (Scioldo, 1991; 2006), spatial distribution maps were obtained over the slope for motion parameters such as velocity, kinetic energy and height from the ground. Combined with the estimates of the “design block” – i.e. a projected block representing the phenomenon – the results of the modelling allowed the planning of countermeasures designed to control and contain the collapse process, based on the installation of suitable rockfall barriers.