Weak points of Sevastopol: experts showed where collapses are possible

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Experts warn of weak points in the city that, in the event of an earthquake, will cause the greatest damage.

In Sevastopol, on Krasnyi Spusk, work is underway to close the slope with a synthetic net to prevent rock falls. It is a necessary and responsible business. The need for such work has matured several decades ago, but the hands of the city authorities then did not reach the solution of an extremely urgent problem. And stones all those years fell on the roadway, and on the sidewalk, and on the roofs of cars and trolley buses …

Rock in motion

Thank God there were no casualties. And only a few witnesses and employees of services involved in cleaning the roads knew about the incidents. The current emergency work to stabilize the slope on the instructions of the State Budgetary Institution “Sevastopol Avtodor” is carried out by the specialists of the Scientific and Production Association Bazaltum. The ledge for the road leading from the current Suvorov Square, more precisely – from Pushkin Street to the railway station, was cut out in soft rocks and was not protected by a retaining wall for a long distance. For the movement of trams, and later trolleybuses, overhead supports were installed. Special niches were cut for the pillars. The most dangerous slope is from the stairs from Ushakov Square to the traction trolleybus substation and the shooting range and to the fence of the Khladokombinat. Near the stairs under Matrossky Boulevard above the roadway there are ruins of masonry, ready to collapse at the slightest vibration of the earth. And Sevastopol belongs to the zone of possible 8-point fluctuations.

From time to time, the slope was cleaned from free-lying stones. But such prophylaxis remained a half-measure and did not provide guarantees of safety. The soil was exposed to precipitation and sun drying. There were also technogenic accidents during the discharge of sewage from Istorichesky Boulevard, during the depressurization of the underground reserve tank with water in the ice cream shop of the Sevastopol Cold Storage Plant. Their consequences were promptly eliminated, the topic was consigned to oblivion until the next incident.

Alexey Fedorov at the living rock block.





For many years, a native Sevastopol resident, a leading geologist of the Krymgeologiya enterprise, Aleksey Fedorov, has closely followed the emerging danger in this area – a moving rock block weighing hundreds of tons. Alexey Pavlovich installed glass beacons on a gypsum solution. And the glasses burst with enviable regularity, which indicated that the block was moving relative to the main body of the wall. The municipal services of the city read the reports of the geologist, but did not show much reaction. Fedorov cited the facts of aeolian erosion of the wall, in which the wind constantly blew out the least durable layers of rock. This effect is named after the ancient Greek god, lord of the wind, Aeolus. The layered “cake” of the mountain massif under Istoricheskiy boulevard was composed of heterogeneous rocks. Part of the sandstone was blown out, forming deep niches long along the front. The “cream” from this “Napoleon” was blown out and washed away, then the “cake”, which had lost its support, collapsed. Aleksey Pavlovich, forty years ago, proposed to concretize problem areas, but the utilities were not heard. There is no other opposition to eolian weathering yet.

The walls of Sevastopol.





Dilapidated state

Another expert on rockfalls and landslides, a first category geologist Sergei Streltsov, for many years pointed out the dilapidation of the stone fence along the eastern perimeter of Istorichesky Boulevard. It was built during the creation of the boulevard as a recreation area for citizens. Later, it was repeatedly repaired and rebuilt in order to prevent the fall of citizens who had pranced from the height of the rock work onto the roadway. The last renovation was carried out in the first five years after the liberation of the city in 1944. The facility had no military significance, no cement or concrete was allocated for its construction and repair. Now the fence is in an extremely dilapidated state and threatens to collapse both individual stones and entire fragments of masonry. According to Sergei Streltsov, stones falling from the height of the fence pick up a decent speed and are able to fly over the carriageway of the descent, bombarding pedestrians on the sidewalk. There were cases when teenagers, out of hooligan motives, threw fence stones down onto the road.

Steltsov on the Red Descent.





An attempt to close the problem wall with synthetic mesh with steel anchors and cable reinforcement will be successful. But only partly. This network will not stop the stones of the collapsing fence. There is only one way out – dismantling the dilapidated fence and building a new concrete one. The second line of the road connecting the station with Suvorov Square is today called the Trolleybus Descent. It’s just that “Trolleybus Ascent” doesn’t sound very euphonious. Now both branches are used for one-way traffic. But during the overhaul of roads in the 80s of the last century, two-way traffic was also temporarily carried out. Opposite the tire station and the old naval food warehouses in the rock mass, underground workings are visible. They were pierced a long time ago and were widely used even during the Great Patriotic War for shelter from air raids. Some of them were laid with masonry, but in vain. At the turn to the Tsarskaya pier, the portal of the Sevgorvodokanal enterprise was equipped. The entrance to the dungeon is securely locked from unauthorized persons and is constantly monitored by specialists. And then the slope is again covered with aeolian weathering of great depth. Vertical cracks are also clearly visible, extending 150-200 meters deep into the massif under the building of the Children’s Naval Flotilla. The massif of the mountain resembles a loaf of bread cut into slices with a sharp knife.

Slope.





Rock displacement

The mapped crevices are located exactly with one azimuth, which characterizes the most powerful tectonic fault. The displacement of rocks along this fault occurred 26 thousand years ago. On the wall, the place of displacement is clearly distinguished by a chaotic pile of rock fragments. On the basis of his conversations with the archaeologists of Tauric Chersonesos, Sergei Streltsov came to the conclusion that 8-point earthquakes in the territory of the southwestern Crimea were also in the time of early Chersonesos. During excavations, under the mighty walls, the remains of civilians with household utensils were found without any connection with hostilities or fires. Sergei Vitalievich does not exclude the possibility of new earthquakes in Sevastopol, albeit of a lesser magnitude. He warns of the weakest points in the city, which, in the event of an earthquake, will bring the greatest destruction.

Southern edge of the Buzin square.





Where the Red and Trolleybus slopes meet, Buzin Square begins. Its southern end is located just above the above-mentioned fault. About five years ago, this edge of the square sagged noticeably, deforming the enclosing stone wall. The subsidence continues. Further, opposite the Children’s Flotilla, a stone parapet stretches, the western side of which looks quite safe, but the eastern one is very badly destroyed and threatens with further collapse. A story about natural and man-made landslides and landslides in the city center would be incomplete without mentioning the square between the Tolstoy Library and the Children’s Art School. Recently, a major overhaul of tile laying has been carried out in the park. The work was done efficiently and on time. There are no complaints about the performers. But the designers clearly did not take into account some factors or deliberately ignored them. The renovation was carried out without comprehensive consideration of the stormwater drainage requirements. As a result, all precipitation collects in the upper part of the retaining wall, the “belly” of which is already very seriously and threateningly bulging over Krasnyi Spusk.

Traces of a tectonic fault: the soil above it subsides.





Incomplete drainage of storm sewers in the park will sooner or later lead to a change in the situation not for the better. Not so long ago, the old dilapidated masonry of the retaining wall to the east of the entrance to the library collapsed on Red Descent. So far, no one undertakes to repair it. Now you can expect the fall of the wall from under the park with a commemorative sign to the battleship “Sevastopol”.

Published in the newspaper “Moskovsky Komsomolets” No. 37 of September 9, 2020

Newspaper headline:
Rockfall on Red Descent

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