Kapadokya Bölgesi’ndeki Kayadan Oyma Yeraltı Depolarının Duraylılığının Değerlendirilmesi

Abstract

Similar to the historical rock structures carved in the ignimbities in the Cappadocia Region, even larger and regularly underground openings are created particularly for the purpose of storing potato and lemon products. However, the unique study conducted on these storages is for the evaluation of heat transfer and energy loss in their surrounding rocks. Based on the results obtained from this thesis study, aiming to investigate geo-engineering problems, which recently occur with the increase in the volume of storage, and the factors affecting the stability of these underground storages, the stability conditions of the storages were assessed and a guidance on the issues to be considered in relation to their planning and excavation stages was proposed. For this purpose; a detailed inventory of the storages, which have been carved in different ignimbrites and were allowed to be examined, geo-engineering data were collected from these storages and the observations were made on the instabilities in some storages, long-time monitoring on temperature and humidity variations in the selected storages, geomechanical properties of ignimbrites were determined by laboratory tests, stability conditions of the storages were assessed for different conditions with the aid of kinematical analyses and 2- and 3-dimensional numerical methods, and in the final stage, a guide for the considerations of planning and excavation stages of the storages was recommended. The results obtained from this study indicated that except those excavated in the Kızılkaya ignimbrite, spalling and ravelling associated with atmospheric conditions will occur in the parts close to the entrances of the storages caved in other ignimbrites, failures may occur in the roofs of storages where the stratification and pyroclastic fallout deposits are located in the roofs and these results are consistent with the observations performed in the storages. According to the kinematical analysis results, it is expected that in the Cemilköy ignimbrite, structurally controlled instabilities would not be expected, whereas in other ignimbrites, it was determined that new wedge blocks could be formed in certain directions with the effect of fault and in order not to cause any threat by these blocks suitable storage excavation directions were recommended. Numerical analyses have shown that with the increase of the inlet distance and pillar widths, the overburden thicknesses, that is necessary to preserve the stability of the storages, will also increase and the width of the storages decreases. In addition, according to these analyses; depending on storage geometry, as the overburden thickness increases, surface cracks may be detected due to tensile stresses developing from the earth surface to the storage ceiling. For each type of ignimbrite examined, the results of 2-dimensional analyses, which were carried out for non-sloping and sloping models with different opening geometries, graphs have been formed and included in the excavation guide based on the geometric features of the storages. Based on the results of 3-dimentional numerical analyses carried out for the sloping, neighbouring and symmetric storage models, in case of thin walled storages, depending on the overburden thickness changes this wall and particularly in storages with square pillar, where the storage will be unstable if the overburden thickness above the storage is 4 m, it was determined that cracks along the line corresponding to the wall between two adjacent storages would develop. The 2- and 3-dimensional analysis results revealed that, instead of square pillars, where failure has been observed in more elements are observed in terms of the stability, the system with strip pillar or lodge system should be preferred and it is necessary to carry out 3-dimensional analysis before the excavation of the storages, which are planned to be excavated particularly with pillar system.