Author: Nikolai Golovkin
15% of the territory of Moscow geologists consider the potentially dangerous area. It is an objective reality that the city has to constantly fight. Says the chief researcher at the Institute of Earth Physics, Professor, Doctor of Geological and Mineralogical Sciences Andrei Nikonov
— Andrey, according to numerous media reports might give the impression that the dips in Moscow — a phenomenon unknown before the Muscovites …
— It is not. The newspaper "Moscow News" in 1871, reported that a minister of one of the cathedrals of the Kremlin for 37 years counted ten cases of failure on the Kremlin hill. They said that crumble dilapidated basement vaults, which were built in large numbers in the fifteenth and sixteenth centuries to shelter citizens from enemy attacks. And ordinary people talked about a heavy jolt of … "Continuous driving of heavy crews." The fact that failures are directly related to karst cavities, then just do not know.
— So this phenomenon "with a beard?"
— Certainly. Only here the scale failures in our day commensurate with what was in the past. Foundation of the city (and not only its central part), pitted and down. And if for the subsidence of the surface near the subway lines instrument observations conducted at the very least, that the behavior of soil over most other cavities is not known. Not even know their location. And it does not control the situation.
— Many still remember how five years ago, the house fell on the Big Dmitrijevka …
— This accident could be called "point." Here, suddenly intensified quicksand, liquefaction occurred when the next pit dug. Karst voids behave differently. For example, construction of a shopping complex near the Manege Square in time triggered subsidence and collapse of underground cavities within a radius of 1.5 kilometers. In some cases, this process was accompanied by a noticeable aftershocks, which recorded instruments. And on the buildings of the Historical Museum, the University, the "Moscow" and "National" cracks were visible to the naked eye. Many Muscovites took for these aftershocks of the earthquake. Something similar is happening in other parts of the city. For example, in Lefortovo, at the intersection of Hospital and Ukhtomskogo shaft, an area of about 1.5 square kilometers in 1995 aftershocks lasted for 2.5 hours, 7-8 times and caused panic among the residents.
— But perhaps even more dangerous flooding of buildings?
— Flooding in Moscow due to the massive leak of water communications, strong changes of underground space and, therefore, a violation of the natural ways and modes of groundwater flow and enhanced irrigation in summer and snow melt over the heat communications during the cold months. The value of groundwater recharge, which create flooding, 2-3 times higher in urban areas than outside it.
The consequences of flooding — the loss of the bearing capacity of soil under buildings, corrosion communications, which often leads to a crash. In asphalt, concreted Moscow during the summer downpours low-lying areas for many hours turn into water bodies. Especially dangerous in this sense the tunnels. Among them Tagan, Warsaw, Arbat, Volokolamsk.
Natural circulation of surface and groundwater in Moscow so corrupt and artificial reservoirs in the city in such a state (65% depreciation), which is almost half of the urban area water is no deeper than three meters from the surface.
— What is the systematic pumping of deep groundwater for water supply and the construction of the subway?
— There was not a drop of water level in the interior ("water table"), but changes in the properties and the state of the rock on which stands Moscow. In some areas, whole areas were in a state of instability, which led to their subsidence, fracturing at depth and, ultimately, failed.