At the 100+ Forum Russia, experts discussed the unique solutions of the Lakhta Center

There are 2,080 piles at the base of the Lakhta Center complex. The most powerful of them, with a diameter of 2 meters and a depth of up to 82 meters, have no analogues in the world. During the construction of the box–shaped foundation of the skyscraper, a new world record was set - the world's most powerful monolithic reinforced concrete slab with a volume of almost 20,000 cubic meters was created.

The unique foundation of the Lakhta Center

The future high-rise dominant of the northern capital, with a design height of 462 meters, has been under the close attention of specialists and experts since the beginning of its foundation. In August 2015, the zero-cycle works were successfully completed. In three years, the following works have been carried out at the facility:
- installation of a "wall in the ground" (enclosing structure along the contour of the foundation of a high-rise building);
- installation of a pile field for a high-rise building;
- excavation of a foundation pit for a high-rise building with a spacer disk system;
- pile foundation of a multifunctional building;
- pile base of the stylobate (parking lot);
- work on the slab grillwork of a multifunctional building;
- works on the construction of a box-shaped foundation of a high-rise building.

At the 100+ Forum Russia 2015 high-rise construction forum, the builders of the complex shared information about the completed stage of work, challenges and unique solutions that were developed during the design and construction process, as well as a unique system for monitoring the quality of work and the condition of structures during operation, developed and implemented specifically for this project.

Sergey Nikiforov, Chief Engineer of IFC Lakhta Center, Igor Bokov, researcher at the Laboratory of Soil Mechanics of the Gersevanov Research Institute of Soil Mechanics of JSC SIC Stroitelstvo, Alexey Shakhvorostov, General Director of Inforsproekt LLC, and Alexey Synchikov, Project Manager of AESOM CSD ltd, took part in the section as speakers.

Record numbers of the foundation of the Lakhta Center

The base of the high–rise building will be a box-shaped foundation, which consists of five walls and two massive horizontal slabs - the lower and the upper:
- the foundation area of the Lakhta Center is 5,600 square meters, height is 17 meters,
- during the continuous concreting of the 3.6-meter thick seamless bottom slab, a new world record was set: 19624 cubic meters of concrete were laid in 49 hours.,
- in the center of the box-shaped foundation, there is a core of rigidity with a diameter of 26 meters at the base, which will take on 70% of vertical loads, therefore, radial walls (beams) are erected between the foundation slabs to evenly distribute the load and create additional rigidity.,
- the 2 m thick top plate is the final element of the box–shaped foundation,
- the box-shaped foundation, in turn , rests on 264 piles with a diameter of 2 m and a length of 65 m.

Each pile is a separate complex structure and carries half a percent of the load of the future building. A very heavy load is placed on the walls of the piles. Therefore, they are embedded in thick layers of Vendian clays, comparable in structure to hard rocks.

Protection from possible water ingress is provided by a "wall in the ground" – a huge pentagonal glass with a depth of 30 meters, which surrounds the foundation and forms a kind of hydraulic lock from groundwater. In this way, the unique reliability and strength of the building's foundation is achieved.

Verified decisions based on accurate data

The type and construction of the foundation were determined on the basis of archival data and large-scale engineering and geological studies conducted by leading specialized organizations - NIIOSP named after. Gersevanova, JSC Trust of Geodetic Works and Engineering Surveys, Su-299. 
An analysis of the results of a complex of field and laboratory studies, as well as joint calculations of the base and the ground part of the tower building confirmed the bearing capacity of the soil mass and the reliability of the selected design solutions.

Control at all stages

Operational control is mandatory at each stage of the work.
After drilling the well, a video camera is immersed at the bottom of each pile. Thus, experts could reliably verify the absence of water and foreign objects at a depth of up to 82 meters.
The density of concrete is checked by ultrasound, and the absence of even the slightest voids, which could subsequently lead to deformations, is established. Ultrasound is also used to check the strength of seams when welding frames. The pile quality is selectively controlled by core drilling.

For reference:

The Lakhta Center is a multifunctional social and business complex, the core of which will be the headquarters of the Gazprom Group of Companies. In addition to offices, the new complex will house the Mir Nauki children's scientific and educational center, exhibition spaces, a planetarium, a medical center, a multifunctional hall for congresses, conferences, theatrical productions, musical and costume performances, a cinema center and a sports center, and a number of other publicly accessible services, including a bank branch, shops, restaurants, cafes, etc. The total area of buildings and structures will be 400,000 m2. The construction of the complex is scheduled to be completed in 2018.

Currently, work is continuing on the construction of above-ground floors of high-rise and multifunctional buildings. Companies with unique technologies, modern high-performance and environmentally friendly equipment and highly qualified specialists were selected to carry out the work on a competitive basis.:
• The general contractor for the construction of the Lakhta Center is Renaissance Construction.
• General Designer - Samsung S&T.
• Work on the installation of "walls in the ground" - CJSC "Geostroy" (St. Petersburg).
• The svay–Bauer device (Germany), Geoisol (St. Petersburg).
• Scientific and technical support of the work is provided by the NIIOSP named after. Gersevanova JSC "SIC "Construction".
• Technical supervision is an international company AECOM.

Detailed information about the project.