# Structural Detection and Restoration Proposal for the Mardin Sahkulubey Cupola
## 1 Introduction  
The basic principle of cultural heritage is that it is invaluable and integral to our future. The built heritage is generally seen as a material element whose historical, documentary, and aesthetic information must be preserved for future generations. The obligation to protect and make it accessible is necessary [1]. Architectural heritage is generally built with natural stone from quarries located in the geographical vicinity. It should be preserved over time, as it is an essential element of people's cultural heritage [2]. This is particularly important in the context of historical architecture, such as palaces, castles, or cathedrals [3]. The conservation of stone heritage is always a delicate and complex challenge. Several variables must be considered to identify the problems, define the necessary conservation measures, and select the materials and processes to use. The factors to be analyzed include the intrinsic stone properties, conservation status, degradation mechanisms, and environmental factors [1, 3]. An in-depth knowledge of building materials is essential to preserve them [3]. A typical restoration practice represents cleaning, repairing, or even replacing the damaged portion of buildings with similar stones. However, the restoration work is only sometimes appropriately performed, either because the repair is poorly conducted, causing further damage, or because the natural stone used for the replacement is poorly chosen. The only way to deal professionally with replacement work is to determine the original stone and use it as a replacement to avoid contrasts in the building, or if the stone is found unsuitable under current conditions, it should be replaced with a suitable replacement after thorough technical assessment [2, 4]. Although Mardin has experienced various historical eras with many linguistic, religious, and cultural differences, it exhibits excellent unity and solidarity, especially in Mesopotamia and Egypt. Artuqids settled in Mardin and established a small kingdom in this city [5]. While under the rule of the Artuqids, Mardin became a central node where caravans from Iran, Azerbaijan, the Caucasus, and Ahlat visited, along with those who set out for pilgrimage [6]. Dunsyir, established as a trade city during the Artuqid period in the south of Mardin, emerged as an essential center [7]. Today, this place is called Kiziltepe. The cupola is a structure found in all regions where Turks reside, from East Turkestan to Anatolia. One is the Sahlkulubey Cupola, located in Kiziltepe, a district of Mardin province, Turkey. The cupola, an important historical, cultural, and spiritual monument, was built by the Artuqid Principality in the 12 th century [8]. It is obligatory to preserve and sustain the quality of the buildings within the scope of the Immovable Cultural Heritage through appropriate restoration and intervention [9]. Re-functioning is an essential issue in the use of historical buildings today and prevents them from being abandoned and deteriorating over time [10; 11; 12; 13]. In a study titled \"Nonlinear Structural Performance of a Historical Brick Masonny Inverted Dome\", the authors determined the average density of the Mardin limestone material to be 2200 kg/m\({}^{3}\) and the compressive strength to be 23 MPa. In the study, the brick's average density and compressive strength were chosen to be 1800 kg/m\({}^{3}\) and 4 MPa, respectively. The average compressive strength of the Cas mortar was taken as 2.5 MPa [14]. In a study titled \"Investigation of engineering characteristics of Mardin stone used in eco-building\", the authors found that the majority of the Mardin stone, with a ratio of 95%, is composed of micritic and crystallized calcite. The specific mass of Mardin stone is 2680 kg/m\({}^{3}\), its water absorption capacity is 13.72%, and its porosity rate is 22.16%. The compressive strength of the stone is 20 MPa, and the tensile strength is 3.73 MPa [15].