Geoenvironmental Characteristics and Stability Problems of Antique Semi-Underground Openings in Konya, Turkey

Abstract

Soft pyroclastics were used mostly in ancient period as underground openings due to their thermal insulation and easy carving properties. In this study, geoenvironmental properties and geoengineering problems of an ancient semi-underground (hill) settlement and a rock-hewn church located in Sille district in Konya carved into blocky pyroclastic deposits is presented. The large part of these man-made historical rock structures have maintained their stability but at the same time that structures suffer from some stability problems generated especially with the predominance of the environmental conditions. It is crucial to determine the physical properties and geomechanical parameters of these blocky pyroclactics and to identify possible rock engineering problems in terms of rock improvement and restoration projects. The stability problems and their causative factors arising from environmental conditions and structural properties were also investigated. The laboratory tests results revealed that strength of the soft welded pyroclastics markedly reduce when it becomes saturated. This result suggests that the failures quite likely occur in rainy seasons due to the increase in water content of the overall rock mass. The pyroclastic deposits that surrounded the historical monuments have been substantially affected by the climatic conditions of the region. On the other hand, it is concluded that the discontinuities seem to be a crucial factor controlling the stability of these structures. Overbreaks, structurally controlled block instabilities, matrix erosion and shearing of the pillars are the dominant stability problems encountered in these rock-hewn openings. Besides an overview was made on possible stability problems at these man-made antique structures to draw attention for preparing future protective measures. Both the historical semi-underground settlement and the church require some protection measures such as installing a drainage system, strengthening the pillars and removing of some dangerous standing rock boulders.