Open pit protection design – residential building, Zagreb
A new residential building is to be constructed at Kukuljevićeva 27 in Zagreb. For this luxury new building with 22 apartments we made the open pit protection design. The construction site is enclosed by the neighboring buildings, and in order to reduce displacement and ensure mechanical resistance and stability, but also usability of the surrounding buildings, the open pit protection by top-down method was chosen as a solution.
The sides of the open pit will be protected by constructing an upright reinforced concrete diaphragm supported by ceiling slabs of the underground floors and by the foundation slab, and by geotechnical anchors in some parts. The ceiling slabs are supported by steel columns that are previously installed directly in the reinforced concrete drilled piles with a diameter of D = 400.0 mm, length L = 7.0 m below the lower level of the reinforced concrete foundation slab. The reinforced concrete diaphragm is designed as a permanent construction of underground floors – a load-bearing and waterproof wall.
Due to architectural and urban requirements, the upper part is secured by constructing a pile wall on the western and northern sides of the open pit. The pile wall consists of reinforced concrete drilled piles with a diameter D = 520.0 mm, and of pile length L = 3.0 to 9.0 m at a horizontal distance of 1.50 m. To secure the pile wall, the installation of geotechnical cable anchors through reinforced concrete piles is planned, with a total length of L = 6.50, 9.0 and 12.0 m at a horizontal distance of 1.50 and 3.0 m. The face of the pile wall constructed using shotcrete. The pile wall was constructed because of the architectural and urban requirements at the location that demanded the open pit be broken at its highest part, i.e., to avoid the uninterrupted vertical face of the open pit.
The building in Kukuljevićeva was strengthened by an earthquake 20% above the high Eurocode 8 for our zone and as such is unique in Croatia.
