Engineering Geology World, Vol. XVI, No. 4/2021
Kochev A.D.
Kochev A.D., 2021. Study of the karst-suffosion funnel formation mechanism in Moscow. Engineering Geology World, Vol. XVI, No. 4, pp. 34–45, https://doi.org/10.25296/1993-5056-2021-16-4-34-45.
Until the end of the 1980s about 42 karst-suffusion funnels were identified in Moscow. The study of the mechanism of their formation was based on the methods of physical modeling using equivalent materials and on the development of deterministic computational mathematical models. The results obtained were used to assess the stress-strain state of karst areas and the parameters of deformations on the earth surface. At the same time, the researchers proposed various mechanisms of the process. When calculating the diameters of karst-suffusion sinkholes and funnels the value of the thickness relative to impermeable clays separating the carbonate massif and covering deposits was used everywhere. The paper discusses a new view on the mechanism of karst-suffusion processes, based on the results of complex engineering-geological studies carried out directly in the areas of funnels’ formation. The complex of methods included the excavation of funnels, geodetic and visual observations of the funnels’ development dynamics and buildings’ deformations, ground geophysical surveys, dynamic sounding, well drilling with a complex of logging and cross-well geophysics, laboratory work, and regime hydrogeological observations. The mechanism of formation of karst-suffosion funnels includes several stages and consists in the destruction of clays from the bottom up under the action of cyclic aerodynamic and hydrodynamic loads caused by sharp fluctuations in the level of fractured-karst waters due to significant pumping. When an open-end disturbance is formed in relatively impermeable clay soils, water-saturated sands are carried out into the karst carbonate massif, and when the decompressed zone reaches the earth’s surface, a karst-suffusion funnel is formed. The thickness of Jurassic and Upper Carboniferous clays does not affect the size of funnels on the earth’s surface, but determines, together with other factors and conditions, the duration of the formation of an open-end disturbance in them. The results of this work, together with previous studies, are the formulation of the mathematical modeling problem of the karst-suffosion funnels’ formation process in Moscow.
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ANDREI D. KOCHEV
Institute Transprojectengineering LLC; Moscow, Russia; a.kochev@mail.ru
Address: Bld. 2, Hse 5, Privolnaya St., 109145, Moscow, Russia