engleski

The significance of structural and geological relationship assessment in the construction of the Ombla underground hydroelectric power plant

The construction design of the underground hydroelectric plant Ombla required geological and structural investigations to be carried out. Due to past earthquakes in the area permanent tectonic movements were inferred. therefore, in the wider and adjanced surroundinga of the Ombla spring it was necessery analyze the structural fabric and the geodynamic characteristics of the area. The most active zone encountered is the front of a thrust fault belonging to the Dinaricum regional structural unut. The compressive regime is maintained as a response to the regional stress of an approximately S-N orientation. Different displacements of various parts of the Dinaricum unit are present. Along the rim of the structural blocks, the Hum-Ombla fault zone exends, accompanied by left transcurrent faults. Through this zone the main groundwater drainage occurs supplying the Ombla spring. In the local Ombla spring area this zone is characterized by three sub-blocks and three major faults. The most important fault for the vital facilities of the Ombla hydroelectric power plant is the Ploeice fault which divides the structural sub-blocks. Along this fault zone there are four mutually connected. The lowest two are active groundwater draining systems supplying the Ombla spring. The data of local stress implies the following deformation of sub-blocks: sub-blocks 2e and 2f are displaced along normal faults from 20o to 30o to the left, downwards, while the sub-block 2 is displaced along the Ploeice thrust fault of 100o to 130o to the left, upwards. The structural data confirmed thad the building of an underground dam with a height from 100 to 130 m was feasible. The connection betwwen the caverns and the fault zone was determined. The unfavorable position of the active Ploeice fault zone imposes the construction of vital Ombla power plant facilities underground.

structural fabric; tectonic movements; underground hydroelectric power plant; Ombla; Dubrovnik

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