Deterioration Assessment of Rock-Carved Historical Structures Using Non-Destructive Testing Methods: A Case Study of Kayadibi Church No. 2 (Konya, Türkiye)

The deterioration processes caused by atmospheric conditions in cultural heritage structures carved into low-strength pyroclastic rocks can result in material loss and weakening of surface integrity over time. In this study, we investigated the current deterioration condition of Church No. 2 in the Kayadibi District of Konya, the largest province of Central Anatolia, Türkiye, where rock-carved cultural heritage structures are extensively located. For this purpose, in situ observations and non-destructive testing (NDT), as well as various physicomechanical tests in laboratory conditions, were conducted to assess the current condition of the monument. Within the scope of the in situ NDT, light detection and ranging (LiDAR), deep moisture (DM), indirect P-wave velocity (VPID), and Schmidt hammer rebound (SHR) measurements were performed. In the laboratory studies, dry density (ρd), apparent porosity (n), water absorption by weight (Wa), cutting rate (CR), penetration rate (PR), SHR, direct P-wave velocity (VPD) and VPID tests were conducted. Using the NDT measurement data obtained from the monument surface, NDT variation maps showing the spatial distribution of these parameters were prepared. Surface deterioration patterns of the monument, documented and classified following the ICOMOS-ISCS terminology, included fractures, contour scaling, black crusts, moisture-related areas, biological colonization, efflorescence, and impact damage. The NDT variation maps revealed that DM values were markedly higher in areas associated with cracks. Strong linear relationships were found between DM and SHR (R2 = 0.87), DM and VPID (R2 = 0.86), and SHR and VPID (R2 = 0.97). These findings highlight the potential of combining moisture measurements, Schmidt hammer testing, and P-wave velocity measurements to characterize spatial variations in the condition of rock-cut heritage structures. However, since the measurements were collected during a single field campaign, the observed relationships should be interpreted as spatial associations rather than evidence of temporal trends or causal relationships.