Development of a hazard assessment model for near surface caves in limestone

Gaziantep is the sixth crowded city of Turkey with a population of about one million. The city contains several near surface man made caves excavated into Oligocone and Miocone age limestone. During the development of the city, many structures were constructed over these caves. Some of them collapsed and caused injuries, lost of life, and properties. The city is still under threat of new collapse of caves and tragedies. This paper describes the methodology developed to prepare geohazard map of potential cave collapse. Developed methodology was based on the determination of global factor of safety (FS) of the cave roofs against failure. Numerical analysis was carried out using 3D finite element method. Three hazard levels were proposed depending on the range of calculated FS namely low, moderate and, high. Geographical Information System (GIS) was used to produce hazard map of caves. The validation of the proposed hazard levels was tested with previously collapsed cave and reasonably good agreement was found. This study is believed to make a great contribution to local municipalities for future development planning of the city.