The necessity of contemporary assessment of the natural hazardous processes on the territory of Bulgaria leading to disastrous and catastrophic situations in a number of regions is motivated by their high activity resulting in destruction of building fund, infrastructure, historicalmonuments, land use disturbance and annihilation of areas, interrupting of communications, aggravation of ecological conditions, human health threats, social stress enhancement. The landslide manifestations displayed recently along the Black Sea coast and the Danubian riparian area, the Rhodopes and other parts of the country and their serious consequences confirm the long ago ascertained truth that the Bulgarian territory is characterized by a high degree of landslide hazard. The geological-tectonic conditions and the relief of the country determine the development of a large number of landslides on its territory. The many years of research and applied activities on landslides have led to the establishment of important relationships for their distribution, factors for origin and activation, mechanism and dynamics, etc. The origin and activation of landslides is a consequence of the influence of many factors — tectonic, seismic, geomorphologic, climatic and technogenic ones. A part of them act permanently, while others have short-term impact. Both separately and in combination they reduce slope stability and provoke the manifestation of big and destructive landslides. The impact of the destabilizing factors and the distribution of 403 landslides are analyzed in this work. Regions with different degree of landslide hazard have been distinguished. Diagrams are shown for the regional distribution and time of landslide display. The weighted effect of the destabilizing factors for slope stability formation is different. A part of them as the contemporary vertical movements and earthquakes are of regional importance, others act locally — erosion, abrasion, precipitation. The origin of the active landslides may be closely related to contemporary tectonic activity. The regional distribution of the landslides according to their volume shows that landslides with a volume up to 10 million m3 are the prevailing type in the country. The most numerous landslides in this group — about 50% of the total number — are observed along high Danubean Bank and Northern Black Sea coast, in the tectonically active grabens as Sofia, Pernik or Simitli and the landslides along some of the faults in the Strouma zone. The largest landslides with a volume of more than 100 million m3 are encountered along the Danubean Bank, the Northern Black Sea coast and in Rhodope Region.
This article examines the stages of construction of infrastructure in Bulgaria. Much of the existing railway infrastructure was built in the late 19th and early 20th centuries, when in practice there were no formulated requirements for assessing the stability of rocky slopes and workings carried out in rocky terrains. For this reason, the development of different methods for assessing the construction qualities of rock massifs is being considered. It is stated that the first methods for estimating the rock massifs are based only on the engineering-geological properties of the rocks, but not on their geostructural features. The development of methods for assessing the stability of tunnels and rock excavations, as well as the entry into them of necessary data from studies on the geostructural properties of rock massifs, are considered. Examples are given of the use of different methods in the assessment of the stability of rock slopes and tunnels in Bulgaria. It is emphasized that in the latest publications, the properties of the rock masses and their stability are described on the basis of the latest knowledge in the field of geostructural geology, geotechnics and normative documents.
The Repository for Radioactive Waste (RAW) Novi Han of the Russian “Radon” type was built in the middle of 60-es, last century, in the Lozen Mountain near Sofia. Unconditioned wastes from medicine, military sources and scientific research activities are stored in it. The repository site has not been selected after detailed geological, hydrogeological and engineering geological investigations including safety assessment procedures. Such investigations were realized in the early 90-es by institutes of the Bulgarian Academy of Sciences. Later, in 2000–2002 the studies of the site have been enlarged with the authors` participation. These newly performed investigations have taken into account the requirements of the International Atomic Energy Agency (IAEA) documents. In the paper the results concerning the engineering geological and hydrogeological settings of the site are presented. Its geological and tectonic conditions are discussed as well. The data will be used for future analyses of impact of the Novi Han repository over the environment including radiological safety assessment.
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