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<p>It is expected that with the increased carbon emission rates around the world impact of global warming will become more severe every year. There are extreme variations in the extent of natural events, such as temperature changes, amount of precipitation, and storm strength. Today, more than 3 billion people live within 200 kilometres inland from the coastline, about half of the world's population. Considering today's cities and population distributions, ongoing research focuses on to what extent they are prepared for these climatic changes and their effects. Especially in megacities close to the shore like Istanbul, buildings, roads, and public transportation networks on the coastline can be damaged due to storm surges and sea level rise from time to time, even in short-term heavy rains. Effect of storm surges and sea level rise effect over mega cities' coastal areas having low-lying topographies have a risk of creating destructive effects. A considerable part of the population of Istanbul, the 1st in Europe and the 14th in the world, with its population approaching 16 million, lives on the shores of the Marmara and Bosphorus. It is crucial for Istanbul, a polycentric city spread over two continents, Asia, and Europe, that the transfer hubs and transportation network provide 24-hour uninterrupted service. However, some metro, tram, ferry, and bus transfer hubs and important stations are only a short distance from the coastline. For this reason, it is essential to determine the hubs and stations at risk in the transportation network, considering storm surges and sea level rise scenarios, considering the disasters experienced in the past. Therefore, the digital elevation maps with 25 meters resolution provided by Copernicus Land Monitoring Service were used to create two scenarios for storm surges and sea level rise to assess the inundation risk of Istanbul's transportation networks close to the coastline. It has been revealed that the transportation network elements located in Kadıköy, Harem and Üsküdar on the Anatolian Side and Beşiktaş, Kabataş, Karaköy and Eminönü on the European Side are at serious risk. As a result of any disaster that may occur in these regions, problems that may cause problems will occur throughout Istanbul and disrupt public transport temporarily. It is planned to prepare more detailed storm surge and sea level rise maps by using high-resolution digital elevation models based on location to define risk in more detail. This way, a practical research output can be provided for research partners and public authorities to develop policies and mitigation strategies for transportation network interruption against storm surges and sea level rise.</p>

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<p>The cracking phenomenon of the brittle rock and rock-like materials (concrete, gypsum) have been widely researched. Such long-standing intensive research requirement is due to the fact that crack initiation, propagation and coalescence are some of the most important parameters for evaluating the rock failure behavior and strength properties. Especially defining the crack initiation stress is a fundamental part of crack propagation that leads to the rock material's final failure. However, due to the nature of rocks, they may have complex inherit structures containing various gaps and void with different sizes and numbers. Rocks mostly tend to have circular and ellipsoidal voids as a result of long and complex geological processes. Owing to this limitation, it is always hard to understand and assess the crack initiation stress comprehensively. Especially for a couple of decades, with the help of developing computer science and technology, numerical models were used on this subject. In this study, various two-dimensional numerical rock models created using Distinct Element Method (DEM) based Particle Flow Code (PFC) were used to understand the effect of different gap geometries over crack initiation stress values of rock materials under uniaxial loading conditions. A base numerical model was calibrated using laboratory test results belonging to basalt rocks. In order to calibrate the numerical model, uniaxial, conventional triaxial and in-direct tensile test results were used. A flat-jointed contact model was chosen to create bonded material during the calibration process. Seven different numerical models were used to investigate the gap geometry effect on crack initiation stress under uniaxial conditions. The base model has a circular gap with 5.40 mm diameter. The other models created to understand the effect of geometry on crack initiation stress have different ellipsoidal geometry depending on the initial circular gap, 1.5 (8.10 mm), 2.5 (13.50 mm) and 3.5 (18.20 mm) times the diameter in the vertical and horizontal direction, respectively. The results of numerical models reveal that the crack initiation stress value decreases with the increase of the gap's vertical length while the width of gaps remains constant. Based on numerical models' results, the crack initiation stress value decreases with the increase of the gap's vertical length while the diameter of gaps remains constant.</p>