The method of multi-electrode electrical soundings (electrical resistivity tomography)

Geoelectric sections of bulk and moraine soils in the band of the design reserve spillway of the hydroelectric power plant dam

At the top – a section with a high-resistance layer of dry bulk sand near the HPP substation covering a thickness of water-saturated moraine loams in the middle part of the projected spillway. Below – a section with a layer of moist alluvial sand and moraine loam, lying on the bedrock dolomites on the site of the projected water dropping sump of reserved spillway in the lower pool of the dam. The manifestations of active and buried karst are outlined in this area, which can be seen in the section of apparent resistances in the form of its lower values, as well as in the sections of P-wave Vp and S-wave velocities according to the seismic survey performed here. During the drilling of geotechnical boreholes the presence of weathered dolomite and dolomite near the border of the moraine and the bedrock surface were revealed.

Geoelectric section of moraine soils along the axis of the emergency spillway

Geoelectric section along the bottom of a deep glacial valley filled with moraine loams and large-block fluvial deposits along the profile.

In the section, by the areas of reduced resistances display the places of the water-saturated moraine loam exit to the earth’s surface. High resistances are characterized the areas with a high content of coarse – grained material – pebbles, rubble, boulders, which is confirmed by the data of cone penetration (CPT) and standard penetration (SPT) tests and drilling. In the initial part of the profile at a depth of more than 20 m, in all probability, the accumulation of large blocks of fluvioglacial material in the edge part of the buried valley is displayed.