Lakhta Center. Zero Cycle. Pile Foundation

Lakhta Center
Underground Cycle
Pile Foundation 260 piles mounted on firm soil will bear the tower loading of Lakhta Center. At a depth of 20m-25m a layer of very firm Vendian clay
occurs serving as a subbase for the foundation. As for its properties Vendian clay is similar to
massive rock. The first objective of the builders is to prepare the site
for the well drilling to follow. From graders the works are switched to drilling rigs. They will pass underground a distance equal to 25 storeys. The first 30m of a well are drilled by using casings. They ensure protection from soil caving and water ingress. The quality of the works is monitored by the specialists by using control video cameras. The next step is
a stage-by-stage lowering of a reinforcement cage comprising a few sections. The specialists strictly observe time intervals. The time between the completion of the drilling and the start of concreting shall not exceed 8 hours. The cage is prefabricated at a plant. At site they are installed and enlarged. A cage is equipped with a duct for conductors transmitting signals from pressure and ultra-sound sensors located throughout the whole pile shaft. These enable to monitor
the state of piles and soil settlement under a pile. Also pressure sensors are installed in individual wells
between larger piles. It allows monitoring the state of soil throughout all the piling. Prior to lowering the sections of a cage are coupled with each other. The height of the structure assembled is
00:02:01,850 –>00:02:06,370
82m. The next step is concreting. Concrete mix is supplied into a well It is done from below to prevent from soil caving. The specialists monitor concrete mix temperature and workability, avoiding any abnormalities. Upon the completion of concreting tremie pipes are extracted from a well. In average a pile bears a loading of 0.4% of the weight of the whole building. Tests demonstrated that the margin of the bearing capacity of piles
exceeds design standards by two times and a half.

Comment here