This article deals with geological aspects of the structure of Poltava loessial upland, which promote the development of soil slips on river valley slopes. The peculiarities of such slopes are specific hydrogeological conditions on the slopes, due to the existence of cloughs in the overlying confining bed. It is proved in the entry, that slope stability depends not only on configuration and on steepness of a slope, but also on conditions and strength of the soil, of which the slope is composed. Soil strength is considerably reduced as a result of their wetness. In recent decades waterlogging has become characteristic not only of Poltava, but also of the majority of Ukrainian cities and towns, that is why activation of soil slips has taken place. There have been analyzed peculiar properties of groundwater unloading in the territory of Poltava from the plateau to the slope of the Vorskla river valley and its influence on the occurrence and development of landslide processes. The emphasis is placed on the occurrence of processes in loess soils, which leads to the decrease in their strength characteristics. It has been revealed that as a result of the formation in the clough of a groundwater flow with higher pressure gradient, strength characteristics are significantly reduced, which is one of the main reasons for the slope stability loss. The search process of cloughs in the overlying confining bed can be simplified by compiling a groundwater surface map. And in order to prevent the occurrence of landslides, it is necessary to construct a map of the waterproof surface on the territory near the slopes.

Full Text

1. Artemenko T. K., Bychkov S. O., 2003. Landslides in severe geological engineering and man-made conditions. The collection of research papers (industrial engineering, construction) (haluzeve mashynobuduvannya, budivnytstvo). Volume 12. Poltava. PoltNTU. Pp. 3-7. (In Ukrainian).
2. Bida S. V., 2011. The peculiarities of strike-slip processes on river valley slopes. Engineering structures (Budivel'ni konstruktsiyi). Volume 75. In two issuess. Iss. 2. Kyiv. State Enterprise “State Research Institute of Building Constructions”. Pp. 371-377. (In Ukrainian).
3. Bida S. V., Velykodnyj Yu. J., 2004. Minor flooding of Poltava and its impact on the development of strike-slip processes. Engineering structures (Budivel'ni konstruktsiyi). Volume 61. Kyiv. State Enterprise “State Research Institute of Building Constructions”. Pp. 275-278. (In Ukrainian).
4. Velykodnyj Yu. J., Bida S. V., Yagolnyk A. M., Peter B. M., Kashlykov M. P. 2003. Groundwater unloading of Poltava table-land. Urgent solutions of the problem of subsoil waterlogging of cities, towns and urban-type settlements (Nahal'ni pytannya vyrishennya problemy pidtoplennya gruntovymy vodamy terytoriy mist ta selyshch mis'koho typu). Proceedings of the international research-to-practice conference (28-31 October, 2003, Kharkiv). Kyiv, Znannya. Pp. 53-54. (In Ukrainian).
5. Demchyshyn M. G., 1992. The current dynamics of slopes on the territory of Ukraine (engineering and geological aspects). (Sovremennaja dinamika sklonov na territorii Ukrainy (inzhenerno-geologicheskie aspekty)). Kyiv, Naukov adumka, 254 p. (In Russian).
6. Velykodnyj Yu. J., 2006. Safeguarding territories from landslides: the study guide (Zakhyst terytoriy vid zsuviv: Navchal'nyy posibnyk). Poltava. 116 p. (In Ukrainian).
7. Zocenko M. L., Velykodnyj Yu. J., Bort O. V., Bida S. V., 2008. The peculiarities of evaluation of slope stability of Poltava loessial table-land. Engineering structures (Budivel'ni konstruktsiyi). Volume 71. In two issuess. Iss. 2. Kyiv. State Enterprise “State Research Institute of Building Constructions”. Pp. 178-189. (In Ukrainian).
8. Information year book concerning activation of dangerous exogenous geologic processes on the territory of Ukraine according to the data from monitoring of EGP (Informatsiynyy shchorichnyk shchodo aktyvizatsiyi nebezpechnykh ekzohennykh heolohichnykh protsesiv na terytoriyi Ukrayiny za danymy monitorynhu EHP). Kiev. State Service of Geology and Mineral Resources of Ukraine, State Research and Production Enterprise “State Information Geological Archive of Ukraine”, 2012. 105 p. (In Ukrainian).
9. Kraev V. F., 1971. Engineering-geological characteristics of ettles (massive material) of Ukrainian loessial assemblage. (Inzhenerno-geologicheskaya harakteristika porod lessovoy formatsii Ukrainyi). Kyiv, Naukov adumka, 228 p. (In Russian).