THE DISGHARGE OF GROUNDWATER ON SLOPES OF RIVER VALLEYS AND ITS IMPACT ON LANDSLIDESDEVELOPMENT (USING THE EXAMPLE OF THE SLIDE IN INSTYTUTSKYI PRORIZ, POLTAVA)
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.