Scholarly record

ENGINEERING GEOLOGICAL CONDITIONS IN THE RIPARIAN AREA OF THE TOWN OF RUSE

J. Evlogiev, M. Nedelcheva, V. Petrova, P. Slavov

Abstract

In 2009 engineering geological zoning of the riparian area of the town of Ruse, including the Danubian bank, the low floodplain terrace, the loess slope and the terraces T3,4, was carried out by the Geotechnical Research Station. The ports, the park, the Sextaginta Prista Roman fortress, the central urban part with impressive architectural ensembles and part of the West Industrial Zone are found in this area. The investigations were conducted within the frame of a contract with the Ruse municipality. Since the origin of the town till present days construction is under the impact of the some processes of the geological hazard – river erosion, loess collapse, settlement of technogenic embankments, high seismicity. Four typical sections are distinguished on the basis of geomorphologic and engineering geological analysis and the extent of manifestation of the geological hazardous processes. Section І. This area comprises the high terraces with collapsible loess of the II type. The section is characterized by the following specific features: presence of loess with collapsible zone thickness of 10-12 m; dense construction, most of the buildings being without measures against collapsibility; depreciated (outdated) water supply and sewage (WS\&S) system that has provoked collapse of the loess base and deformation of 25 buildings; existence of non-compacted embankments in the old part of the town, where most of the WS\&S accidents occur. Section ІІ. It includes the slope between the high and the low floodplain terrace, built of collapsible loess of the II type. The section is under the impact of the following processes of geological hazard – shallow slides, collapse of loess blocks, erosion, earthquakes and collapse of old galleries. The enumerated processes exhibit slight to medium display and only in single places endanger the slope stability. Section ІІІ. The low floodplain terraces of the Danube and Rusenski Lom Rivers, which are built of alluvial and anthropogenic soils, belong to this area. The section is under the effect of: river erosion, floods, high groundwater level and settlement of anthropogenic embankments. Here the geological hazardous processes exhibit medium to strong display. Section ІV. It includes the gully valleys and the big steppe limpets. This is the section with the lowest manifestation of the geological hazardous processes – the erosion in the gullies has been ceased, the loess in the lowest part of the gullies is strongly altered and non-collapsible and the periphery is with collapsibility of the I type. The infrastructure and the building fund in the distinguished sections are affected to a different extent by the mentioned geological processes. Detailed geotechnical analysis is made in the present work and recommendations are given for the rational restriction of hazardous processes. The recommendations are connected with strict adherence to the normative design basis, use of modern methods for engineering geological investigations and application of already approbated under the conditions in the town of Ruse technologies for strengthening the ground base, as well as methods for stabilizing the foundations and the ground base of deformed buildings. The approach in the proposed work may be also applied as a model for analysis and solution of geotechnical problems in other towns along the Danube River.

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