The identification and evaluation of the usage areas, physical, and mechanical properties of brick materials on the walls between Diyarbakir Mardin gate and new gate segments of the city walls

In past periods, people used the materials they could obtain based on the geography they lived in to build structures. Stone and wood are materials that can be found in some regions and used directly without any processing. In regions where stone and wood were not available, people tried to produce building materials using soil. For this purpose, adobe was the first material discovered. Due to its short lifespan and quick deterioration under external factors, adobe was eventually replaced by brick. Brick is a material obtained by mixing clay, clayey soil, and water, shaping it, drying it, and then firing it. The use of brick material in buildings first started during the Neolithic period. Excavations have revealed that the oldest bricks were discovered along the banks of the Jordan River during this period. The use of brick material later became widespread in civilizations such as Iran, India, Central Asia, Mesopotamia, Anatolia, China, Rome, Byzantium, and the Ottoman Empire. In traditional buildings, brick material was used in vertical load-bearing elements such as walls and piers, and in horizontal load-bearing elements such as floors, beams, arches, vaults, domes, and transition elements (such as trompes, pendentives, and Turkish triangles). Diyarbakır, a historical city located in southeastern Turkey, has been ruled by many civilizations. The most important structure built by these civilizations in the city, which has become a symbol of the city, is the Diyarbakır walls. Listed as the Diyarbakır Fortress and Hevsel Gardens in the UNESCO Cultural Heritage List, these historic walls have four main gates: Mardin Gate, Dağ Gate, Yeni Gate, and Urfa Gate. In this thesis study, the brick material found in the wall sections and bastions between Mardin Gate and Yeni Gate, which surround the southeastern section of the Suriçi Region, was examined. In the wall sections and bastions in the region, it was observed that brick material was generally used in horizontal load-bearing elements such as coverings (arches, domes, vaults, and transition elements), occasionally in beams, and to a lesser extent in walls and piers. The stacking and bonding techniques of the used brick material were observed and documented with photographs during the fieldwork. It was observed that the brick material, which was generally stacked horizontally in walls, beams, domes, and vaults, was not used for decorative purposes in this bonding technique. In the exception of Bastion No. 55, it was seen that horizontal-vertical stacking was used in the vaults on the first floor, and in the domes on the first floor of Bastions No. 55 and 63, horizontal-vertical stacking technique was used; and the bricks in the dome skirts and pendentives were placed protruding outward and angled, gaining a decorative purpose. In arches, brick material was generally used in double rows, occasionally in single rows. Structural problems occurring in the structural elements where brick material was used were observed during the fieldwork. The structural problems observed in the brick material included brick material losses, cracks, wear and surface losses, microorganism and plant formation, xxiv salting, and soot accumulation. After observational detections, experiments were conducted to determine the physical and mechanical properties of brick samples taken from Bastion No. 63 (Fındık Bastion) and Bastion No. 64, which had structural problems. The experiments conducted to ensure the preservation and sustainability of the brick material used in the wall sections and bastions included the uniaxial compressive strength test, point load strength index test, water absorption test, freeze-thaw test, ultrasound test, and SEM/EDX analysis. The data obtained from the test results were evaluated by converting them into graphs. Based on the observational detections and data obtained from the test results, the structural properties of the brick material used in the wall sections and bastions between Mardin Gate and Yeni Gate were determined. This thesis study was completed with the aim of being an up-to-date resource for both restoration and academic studies by conducting experimental studies on the selected wall sections and bastions through a comprehensive literature review.