Field and river

20th International Conference of Ethiopian Studies (ICES20)
Mekelle University, Ethiopia

"Regional and Global Ethiopia - Interconnections and Identities"
1-5 October, 2018

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BLEN Taye Gemeda, School of Geography and the Environment, University of Oxford, UK

Rock-hewn churches are made using the existing setting of the stone outcrop and adopting the natural morphology of a site to create new spaces. This style of construction has been employed to construct over two hundred churches in Northern Ethiopia. Some of the most famous churches built in this style are the eleven rock-hewn churches of Lalibela which were built in the medieval times. These churches are carved into the slope of a basaltic scoria hill and are found at an elevation of 2430–2550m a.s.l. Its unique architectural style has earned this site a place in the UNESCO world heritage list. Studies on the churches of Lalibela have mainly focused on the method of construction, analysis of archaeological evidence, and the historical significance of the town of Lalibela. More recently, researchers have studied the petrographic characterization of the stone, the slope stability of the site, and the geotechnical properties. These papers have shown that cracks and fractures are common features on all the churches and that there is an urgency to understand their vulnerability to environmental and manmade agents. Therefore, the objective of this research will be to determine the extent to which cracks, fractures, and discontinuities destabilize the structural integrity of the churches and the role inherent properties of the stone plays in developing these cracks and fracture. The following methods will be employed to carry out this research: 1) laboratory techniques will be used to investigate the stress swelling clay mineral may be causing on existing fractures with repeated wetting and drying cycles; 2) non-destructive techniques will be used to investigate the material properties of the stone in situ; 3) finite element modelling will be used to map the stress distribution and to simulate the response of the structures to additional loads. Such a holistic approach is necessary to characterize the properties of a heterogeneous and anisotropic lithotype like the basaltic scoria. Moreover, measuring the stability of the cracks and fractures will be useful for future research work in conservation of these monuments as well as for restoration works being conducted in Lalibela.