How to build a skyscraper "in the swamp"?
When the construction of the Lakhta Center began, the buildings weighing almost 600 thousand tons, one of the main questions from observers was associated with the notion that “Petersburg stands in the swamp” and to build buildings of the “super heavyweight” category is impossible in principle - suck.
At that time, there were many theories. In the top, perhaps, you can put up a couple of apocalyptic scenarios that “the tower pushes the earth to magma”, and “the tower slides into the Gulf of Finland, raises the tsunami and the giant wave will wash away the Zenit-Arena and everything else. Maybe even like this:
')
Is it worth having fun on these hypotheses? Is the soil suitable for heavyweight buildings in Petersburg? If not, what technologies allow you to say yes? If so, where did the “swamp” idea come from?
We offer to understand the series of thematic posts. Let's start with the ground situation in the city - after all, it is the fertile ground for “swamp disputes”. Next, let's move on to the project itself.
The first thing that comes to mind when discussing the bearing capacity of soils is to turn to the historically established experience. How was the whole city built up in a swamp?
The construction of the abutment for the New St. Isaac's Bridge. Lithograph by Tretter's drawing ( Source )
So, St. Petersburg appeared on the flat, “mossy, muddy shores” of the Neva delta. You can't tell more precisely - up to 75% of the territory lined for the creation of the Venice of the North was swamped.
One of the maps of the area, the 17th century. (Photo from here )
It seems that the soils are really "not lucky." But then the builders didn’t think much about it - they just built, thanks to, the methods gained by experience allowed. The methods were adopted, including from Peter Holland, beloved by Peter, where the ground was no better, and the buildings were fine.
The royal palace in Amsterdam to this day steadily rests on its 13.5 thousand wooden piles. (Photo from here )
The construction of Petersburg began with the layered foundations of oak logs, which were previously soaked — that is, they “starved” in the water to increase the strength of the wood. Moorish piles, 6-8 meters long, were driven into the ground to seal it, and covered the “pile field” with wooden flooring.
View of wooden piles (Kennigsberg, photo from here )
Another version of the St. Petersburg foundations - in a trench on the basis of the boulders laid a rubble stone (limestone, granite).
Example of rubble foundation
To this day, most of the buildings of the historic center are on the foundations of these types. You can not go wrong if you assume wooden lying or rubble stone under the houses on St. Isaac's Square, Nevsky Prospect.
And under the Moscow railway station, too. In the middle of the 20th century, wooden lezhne under the building was antiseptic, mothballed, the ground was strengthened.
Our contemporaries have already found out that the saturated soil for such foundations is not an enemy, but an ally. Groundwater protects wooden piles and decks from destruction, preventing contact with air. At a time when buildings were erected, the builders did not yet know. It turns out that the “bad” ground helped the centuries-old buildings in St. Petersburg. Here is a paradox.
For two centuries, the St. Petersburg buildings did not grow above 23.4 m. The red line is the eaves of the Winter Palace. The violator is St. Isaac's Cathedral, whose height 101.5 m exceeded the regulations 4 times.
He, with a weight of 300 thousand tons, became a pioneer in the heavyweight category.
The creation of Montferrand proved that building high and heavy is possible even on weak ground. How?
Saint Isaac's Cathedral. Author photo - Priest Maxim. The length of the building is 102 m., Width is 92 m., Height is -101.5 m.
The key point - the massiveness of the temple structures provided him with high spatial rigidity. The walls of the cathedral in thickness - from 2.5 to 5 m, arches - 1.25 m. Pyramidality helped to distribute the pressure of the building on the ground.
One of 49 lithographs of Montferrand, telling about the construction.
The way of arranging the foundation was not technologically different from those described above, but it shocked the scale of the work.
The depth of the pit is 5 m. It has 37 thousand wooden piles!
The soil between the piles is compacted with rubble and spilled with a lime-sand mortar.
Limestone slabs and granite blocks are laid on top. Plate thickness - 7.5 m., And weight - 100 thousand tons! - one third of the weight of the cathedral.
These parameters will remain unsurpassed until the end of the era of wooden-rubble foundations.
The height of the Soviet buildings in St. Petersburg remained pre-revolutionary throughout the first half of the 20th century. Including because geotechnologies did not change.
In the 60s precast reinforced concrete piles appeared, the background building immediately made a jump to 14 floors. In 1975, two 22-storey houses- “plates” were commissioned, 76 meters in height.
22-etazhki near Victory Square (end of Moscow Avenue) (Photo from here )
In the second half of the 1990s, modern foreign geotechnologies make their way to us.
New foundations - new heights. Today in St. Petersburg there are more than 3.5 hundred buildings from 75 to 100 meters tall. Not yet skyscrapers, but for pliable soils, and this is already too much?
The question of the suitability of soft soils for skyscrapers without granite scientific knowledge does not understand.
Turn to "Marx."
The word "primer" comes from German and means "foundation." It is not only the soil or the ground under our feet.
Subsoil formation in section
( Source )
A typical soil in the Neva floodplain has the following layers (cited by Dr. Sc., Prof. SI Alekseev):
1. Technogenic deposits with a capacity of 2-3 m.
The cultural layer is attributed to the technogenic soil (Photo from here )
2. Delta deposits (sands from dusty to medium size interlayered and wedged out among themselves) with a capacity of up to 5-6 m.
3. Sea deposits (sandy loam and loam from soft-plastic to flowing consistency) with a capacity of up to 12-16 m.
4. Glacial moraine deposits in the form of loams and sandy loams of a refractory consistency, located at a depth of 20 m.
Such boulders are also characteristic of the moraine - at the construction site “Lakhta Center” they had to be “warmed” with them. This representative was photographed in the Lomonosovsky district of St. Petersburg, photo from here .
And what is below minus 20 meters?
Petersburg is located at the junction of the Baltic (Fennoscandinavian) shield and the Russian (East European) platform.
Edge seam between the Baltic Shield (the shield itself is marked with 1) and the Russian Platform ( Source )
The Baltic shield consists of solid crystalline rocks. And the platform has a two-story structure. The ground floor is also crystalline rocks of the most ancient Archean-Proterozoic age (4-2.5 billion years ago) - granites, gneisses, diorites, etc.
These stones are from the era of the birth of life on earth.
Within St. Petersburg, the crystal floor lies deep - from minus 140 m in the Kurortny district to minus 300 m in the south of the city.
As the environment for the placement of underground objects, this floor is not yet considered, for obvious reasons - too deep.
The upper floor consists of sedimentary rocks. They are different in age, origin, composition, condition and properties. The approach to assessing their sustainability, respectively, is also different.
So, in the northern and central parts of the city, under the Quaternary layer (that is, formed in the modern geological epoch), Upper Kotlin clay is deposited in the upper Vendian. They are also in the south, under the lower Cambrian layer.
( Source )
The thickness of these deposits from 12-20 m to 95-126 m.
But the density of crystalline rocky soil: from 1.2 to 2.5 g / cm3 (GOST 25100-2011).
From the comparison it is clear why in the story we dug so long before these clays. They are the most stable medium available for placing underground structures. And nothing to do with the "swamp".
It is in the Upper Kotla clay that deep sewers are laid, in the same place - the main part of the tunnels and stations of the St. Petersburg metro.
Ride the subway - a journey through the Upper Vendian period (Photo from here )
Of course, the reference for high-rise construction is rocky ground.
Such as under New York. There is only 10-20 meters to it. The stratum (which cannot be called the stratum) sediments pass through shallow piles.
Photos from the conduct of underground work in the center of New York gives a visual representation of the quality of the soil, giving the opportunity to nonstop construction. (Photo from here )
In St. Petersburg, as we have established, to the rocky base (this is the lower "floor" of the Russian platform) is, on average, 200 meters and cannot be used as a bearing layer.
Sedimentary construction demands a lot from the construction of high-rise buildings: it is necessary to ensure spatial rigidity and stability. The design must resist not only compressive but also flexural and torsional loads. Such properties have frameworks of metal or reinforced concrete. In world practice, it was adopted from the first third of the twentieth century.
Petersburg is not the only city where you have to build, based on sediment. The skyscrapers of Frankfurt am Main and Berlin feel great on this basis. Weak ground in China. For example, in Shanghai, for a point skyscraper make a large podium in the form of a powerful box, to reduce the load on the ground. The skyscraper itself is 50x60 meters, and under it is a podium of 20-30 thousand square meters. Under the box - also piles.
The skyscrapers of Shanghai are not only on soft ground, but also are heaped. (Photo from here )
In 2013, the first St. Petersburg skyscraper was erected on the Constitution Square. It was the “Leader Tower”, 140 meters, 42 floors. He does not reach the official “skyscraper” status quite a bit - 10 meters, but we think that in the context under discussion one can close his eyes to this.
„Leader Tower“. By the way, the high-rise building here, between the two buildings of LenEnergo, was planned in the 1980s. Photo by Black_Man from the forum skyscrapercity.com
About the design features of the project authors report:
The Foundation Tower "Leader Tower" photographed Flatron, also from the forum skyscrapercity.com
Construction of elevated levels. Photos from the same place, the author - Star2007
Until July 2016, the Leader Tower was the tallest building in the city (excluding the television tower), then it was overtaken by the Lakhta Center. This is where the fun begins. Petersburg soil has not yet experienced such pressure as in Lakhta. But about it - next time.
Read in the new “series” - who investigated the suitability of the soil under the “Lakhta Center”, why did the researchers dig up to minus 150 meters, did they find the Baltic shield and generally like there, below?
At that time, there were many theories. In the top, perhaps, you can put up a couple of apocalyptic scenarios that “the tower pushes the earth to magma”, and “the tower slides into the Gulf of Finland, raises the tsunami and the giant wave will wash away the Zenit-Arena and everything else. Maybe even like this:
')
Is it worth having fun on these hypotheses? Is the soil suitable for heavyweight buildings in Petersburg? If not, what technologies allow you to say yes? If so, where did the “swamp” idea come from?
We offer to understand the series of thematic posts. Let's start with the ground situation in the city - after all, it is the fertile ground for “swamp disputes”. Next, let's move on to the project itself.
The construction paradox of Petersburg: water in the ground is not an enemy, but an ally
The first thing that comes to mind when discussing the bearing capacity of soils is to turn to the historically established experience. How was the whole city built up in a swamp?
The construction of the abutment for the New St. Isaac's Bridge. Lithograph by Tretter's drawing ( Source )
So, St. Petersburg appeared on the flat, “mossy, muddy shores” of the Neva delta. You can't tell more precisely - up to 75% of the territory lined for the creation of the Venice of the North was swamped.
One of the maps of the area, the 17th century. (Photo from here )
It seems that the soils are really "not lucky." But then the builders didn’t think much about it - they just built, thanks to, the methods gained by experience allowed. The methods were adopted, including from Peter Holland, beloved by Peter, where the ground was no better, and the buildings were fine.
The royal palace in Amsterdam to this day steadily rests on its 13.5 thousand wooden piles. (Photo from here )
The construction of Petersburg began with the layered foundations of oak logs, which were previously soaked — that is, they “starved” in the water to increase the strength of the wood. Moorish piles, 6-8 meters long, were driven into the ground to seal it, and covered the “pile field” with wooden flooring.
View of wooden piles (Kennigsberg, photo from here )
Another version of the St. Petersburg foundations - in a trench on the basis of the boulders laid a rubble stone (limestone, granite).
Example of rubble foundation
To this day, most of the buildings of the historic center are on the foundations of these types. You can not go wrong if you assume wooden lying or rubble stone under the houses on St. Isaac's Square, Nevsky Prospect.
And under the Moscow railway station, too. In the middle of the 20th century, wooden lezhne under the building was antiseptic, mothballed, the ground was strengthened.
Our contemporaries have already found out that the saturated soil for such foundations is not an enemy, but an ally. Groundwater protects wooden piles and decks from destruction, preventing contact with air. At a time when buildings were erected, the builders did not yet know. It turns out that the “bad” ground helped the centuries-old buildings in St. Petersburg. Here is a paradox.
Heavyweight: St. Isaac's Cathedral
For two centuries, the St. Petersburg buildings did not grow above 23.4 m. The red line is the eaves of the Winter Palace. The violator is St. Isaac's Cathedral, whose height 101.5 m exceeded the regulations 4 times.
He, with a weight of 300 thousand tons, became a pioneer in the heavyweight category.
The creation of Montferrand proved that building high and heavy is possible even on weak ground. How?
Saint Isaac's Cathedral. Author photo - Priest Maxim. The length of the building is 102 m., Width is 92 m., Height is -101.5 m.
The key point - the massiveness of the temple structures provided him with high spatial rigidity. The walls of the cathedral in thickness - from 2.5 to 5 m, arches - 1.25 m. Pyramidality helped to distribute the pressure of the building on the ground.
One of 49 lithographs of Montferrand, telling about the construction.
The way of arranging the foundation was not technologically different from those described above, but it shocked the scale of the work.
The depth of the pit is 5 m. It has 37 thousand wooden piles!
Of these, 24,000 pieces, from 6.3 to 8.4 meters long, were installed by builders from the “team” of Montferrand.
13,000 piles, ranging in length from 8.4 to 10.5 m. - were inherited from the predecessor cathedral - the one that was built according to the design of Rinaldi, but was “unsuccessful”. The inheritance, by the way, turned out to be sideways - it was this pile section that subsequently sagged ahead, causing deformations.
The soil between the piles is compacted with rubble and spilled with a lime-sand mortar.
Limestone slabs and granite blocks are laid on top. Plate thickness - 7.5 m., And weight - 100 thousand tons! - one third of the weight of the cathedral.
These parameters will remain unsurpassed until the end of the era of wooden-rubble foundations.
When the city began to grow up
The height of the Soviet buildings in St. Petersburg remained pre-revolutionary throughout the first half of the 20th century. Including because geotechnologies did not change.
In the 60s precast reinforced concrete piles appeared, the background building immediately made a jump to 14 floors. In 1975, two 22-storey houses- “plates” were commissioned, 76 meters in height.
22-etazhki near Victory Square (end of Moscow Avenue) (Photo from here )
In the second half of the 1990s, modern foreign geotechnologies make their way to us.
New foundations - new heights. Today in St. Petersburg there are more than 3.5 hundred buildings from 75 to 100 meters tall. Not yet skyscrapers, but for pliable soils, and this is already too much?
What is near Petersburg
The question of the suitability of soft soils for skyscrapers without granite scientific knowledge does not understand.
Turn to "Marx."
The word "primer" comes from German and means "foundation." It is not only the soil or the ground under our feet.
Subsoil formation in section
Soil - multicomponent dynamic systems (rocks, soils, sediments and man-made formations), considered as part of the geological environment and studied in connection with the engineering and economic activities of people. (GOST 25100-2011)
( Source )
A typical soil in the Neva floodplain has the following layers (cited by Dr. Sc., Prof. SI Alekseev):
1. Technogenic deposits with a capacity of 2-3 m.
The cultural layer is attributed to the technogenic soil (Photo from here )
2. Delta deposits (sands from dusty to medium size interlayered and wedged out among themselves) with a capacity of up to 5-6 m.
3. Sea deposits (sandy loam and loam from soft-plastic to flowing consistency) with a capacity of up to 12-16 m.
4. Glacial moraine deposits in the form of loams and sandy loams of a refractory consistency, located at a depth of 20 m.
Such boulders are also characteristic of the moraine - at the construction site “Lakhta Center” they had to be “warmed” with them. This representative was photographed in the Lomonosovsky district of St. Petersburg, photo from here .
And what is below minus 20 meters?
Shield and platform
Petersburg is located at the junction of the Baltic (Fennoscandinavian) shield and the Russian (East European) platform.
Edge seam between the Baltic Shield (the shield itself is marked with 1) and the Russian Platform ( Source )
The Baltic shield consists of solid crystalline rocks. And the platform has a two-story structure. The ground floor is also crystalline rocks of the most ancient Archean-Proterozoic age (4-2.5 billion years ago) - granites, gneisses, diorites, etc.
These stones are from the era of the birth of life on earth.
Within St. Petersburg, the crystal floor lies deep - from minus 140 m in the Kurortny district to minus 300 m in the south of the city.
As the environment for the placement of underground objects, this floor is not yet considered, for obvious reasons - too deep.
The upper floor consists of sedimentary rocks. They are different in age, origin, composition, condition and properties. The approach to assessing their sustainability, respectively, is also different.
Here we turn to the analysis of the "Engineering and geological conditions of St. Petersburg", performed by a group under the guidance of Prof. Dr. med. Dashko.
So, in the northern and central parts of the city, under the Quaternary layer (that is, formed in the modern geological epoch), Upper Kotlin clay is deposited in the upper Vendian. They are also in the south, under the lower Cambrian layer.
( Source )
The thickness of these deposits from 12-20 m to 95-126 m.
Verkhnekotlinsky clay is a dense ( density of 2.17-2.24 g / cm3 ) solid silty (dusty) thin-layer differences of greenish-gray color.
But the density of crystalline rocky soil: from 1.2 to 2.5 g / cm3 (GOST 25100-2011).
From the comparison it is clear why in the story we dug so long before these clays. They are the most stable medium available for placing underground structures. And nothing to do with the "swamp".
It is in the Upper Kotla clay that deep sewers are laid, in the same place - the main part of the tunnels and stations of the St. Petersburg metro.
Ride the subway - a journey through the Upper Vendian period (Photo from here )
“Upper Kotla clay is often called“ Proterozoic ”, which is not entirely accurate. Their age is the upper Vendian (the upper part of the Proterozoic) —the interval is 680 ± 20 - 570 ± 20 Ma. This is one of the most ancient sediments of the planet. "
Sedimentary and non-stop construction
Of course, the reference for high-rise construction is rocky ground.
Such as under New York. There is only 10-20 meters to it. The stratum (which cannot be called the stratum) sediments pass through shallow piles.
Photos from the conduct of underground work in the center of New York gives a visual representation of the quality of the soil, giving the opportunity to nonstop construction. (Photo from here )
In St. Petersburg, as we have established, to the rocky base (this is the lower "floor" of the Russian platform) is, on average, 200 meters and cannot be used as a bearing layer.
Sedimentary construction demands a lot from the construction of high-rise buildings: it is necessary to ensure spatial rigidity and stability. The design must resist not only compressive but also flexural and torsional loads. Such properties have frameworks of metal or reinforced concrete. In world practice, it was adopted from the first third of the twentieth century.
Petersburg is not the only city where you have to build, based on sediment. The skyscrapers of Frankfurt am Main and Berlin feel great on this basis. Weak ground in China. For example, in Shanghai, for a point skyscraper make a large podium in the form of a powerful box, to reduce the load on the ground. The skyscraper itself is 50x60 meters, and under it is a podium of 20-30 thousand square meters. Under the box - also piles.
The skyscrapers of Shanghai are not only on soft ground, but also are heaped. (Photo from here )
So what about the skyscraper "in the swamp"?
In 2013, the first St. Petersburg skyscraper was erected on the Constitution Square. It was the “Leader Tower”, 140 meters, 42 floors. He does not reach the official “skyscraper” status quite a bit - 10 meters, but we think that in the context under discussion one can close his eyes to this.
„Leader Tower“. By the way, the high-rise building here, between the two buildings of LenEnergo, was planned in the 1980s. Photo by Black_Man from the forum skyscrapercity.com
About the design features of the project authors report:
“About 800 piles are in the foundation of the tower, which are supported by a solid layer of clay. In the center of the building is the core of stiffness in which the lift shafts are located. Column spacing - 6x6 m “
The Foundation Tower "Leader Tower" photographed Flatron, also from the forum skyscrapercity.com
Construction of elevated levels. Photos from the same place, the author - Star2007
Until July 2016, the Leader Tower was the tallest building in the city (excluding the television tower), then it was overtaken by the Lakhta Center. This is where the fun begins. Petersburg soil has not yet experienced such pressure as in Lakhta. But about it - next time.
Read in the new “series” - who investigated the suitability of the soil under the “Lakhta Center”, why did the researchers dig up to minus 150 meters, did they find the Baltic shield and generally like there, below?
Source: https://habr.com/ru/post/370071/
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