February 1, 2017
Construction on the two-building Mennica Legacy Tower, which will be comprised of a 35-story tower and a 10-story building located in the Central Business District of Warsaw, is progressing nicely. For this project Epstein is serving as the architect and engineer of record, as well as the design engineer for MEP and structural engineering services (Our friends at Goettsch Partners are the design architects).
The construction of the Mennica development, due to the sites relatively high water wall and the adjacent existing subway lines, is utilizing the Slurry Wall or Diaphragm Wall technique. Tom Suarez, PE, SE, Epsteins chief structural engineer and designer of Mennicas structural system explains the use of slurry wall technique for Mennica:
The slurry walls were designed at the perimeter of the below grade levels to accomplish several tasks. The walls are constructed from existing grade before general excavation occurs using a clamshell bucket or rotary auger. As the excavation progresses the void is temporarily filled with a slurry fluid to resist soil pressures and prevent caving. Reinforcing cages are then inserted into the slurry and structural concrete is pumped into the excavation using a tremie pipe to displace the slurry fluid. The result is a structural concrete wall placed deep into the ground without the need for general excavation and forming. Due to the relatively high water table encountered in the area the slurry walls extend 23 meters (75 feet) below grade into non-pervious clay layers to serve as ground water cut-off walls to allow dewatering of the site during basement construction and help to keep the below grade levels dry when in service.
The site is also directly adjacent to existing subway lines which are very sensitive to settlement caused by nearby excavations. The very stiff 800 mm (31 inch) thick slurry walls participate in the earth retention system to effectively protect the adjacent subway tunnels from movement during general excavation. And, once construction is complete the slurry walls serve as the permanent basement walls as well.
Lastly, the slurry wall construction for Mennica is scheduled to be completed at the end of March and the entire development will open in the third quarter of 2019.