Engineering geological properties of the pyroclastic cone-shaped rocky houses of Kandovan, Iran

Kandovan is one of the geo-tourism attractions in the East Azarbaijan Province of Iran, where rural houses were carved within the cone-shaped pyroclastic rocks several hundred years ago. The present paper mainly discusses the effects of climate condition and engineering geology properties on the destruction of these cone-shaped rocky houses. The annual averages of wetting–drying and freezing–thawing cycles are 28 and 14 times, respectively. The greatest impact of these cycles is found to be on physical weathering, which has low resistance to weathering and erosion. Such a low resistance is because of the components of Kandovan rock mass that are largely plagioclase and pumice fragments with low resistance, low welding and sorting, high sphericity, and rounding. Although the weathering and erosion along the existing discontinuities and joints is the most important causative agent of cone-shaped forms, there is a possibility of further damage of the houses due to continuous weathering and erosion potential processes. High porosity, high water absorption, high sensitivity to expansion, contraction by freezing–thawing and wetting–drying cycles; and low strength of Kandovan pyroclastic rocks lead to weathering and disintegration due to environmental impacts. The correlation of physical and mechanical properties of Kandovan pyroclastic rocks and Cappadocian tuffs has shown that the unit weights of rocks are low for both of them. The total porosity of Kandovan rocks is greater than for Cappadocian rocks, while water absorption percent is greater for Cappadocian rocks than for Kandovan rocks. The strength of Kandovan rocks is generally greater than that of Cappadocian rocks.