Investigating the geological and geomechanical characteristics governing the weathering behavior of Meymand tuff

The Meymand world heritage site (Kerman Province, Iran) is a rock-hewn village carved within a pyroclastic rock mass, Meymand Tuff. This site, having an ancient local population with an age of 2000 years, is hosted by a weak rock exposed to deterioration and weathering processes. However, our understanding of the characteristics of the Meymand Tuff is limited to some previous general studies. Therefore, in the present study, the stratigraphy and intrinsic characteristics of the Meymand tuff are investigated to determine its weathering behavior and durability. For this purpose, comprehensive field and laboratory investigations were carried out. The stratigraphy of the valley and the pyroclastic flows that had deposited the Meymand tuff were identified and outlined based on field investigations and many surveyed sections along the Meymand valley. Next, the mineralogical composition, texture, structure, physical and mechanical properties, water absorption rate, slake durability, wetting–drying durability, shrinkage potential of the fine portion, and collapse potential of the Meymand tuff were assessed through laboratory investigations. The results revealed that two pyroclastic flows had deposited the host tuff rocks of the Meymand site. These rocks have a heterogeneous texture comprising very coarse-grained clasts to the fine-grained matrix. Rock characteristics including heterogeneous texture, high porous and open structure, clay-rich mineralogical composition, high water absorption capacity, and swelling and shrinkage potential of the fine portion of the matrix have resulted in adverse behaviors in Meymand tuff. These behaviors are pertained to the strength softening, weight loss, and deterioration at wetting drying cycles. This study was funded by a grant from Iran National Science Foundation (INSF) (98001268).