An underground car park is being built from top to bottom on the shore of Lake Balaton.

We previously reported that the late modern Móló Hotel in Siófok, which had become a safety hazard, late modern Móló Hotel in Siófok, which had become life-threatening, will be replaced by a five-storey contemporary building. The Hotel Apartment will be built directly on the shore of Lake Balaton, and its special features will include a two-storey underground car park and a design with near-zero energy consumption.

The investment also affects the townscape of Siófok, where SWIETELSKY Magyarország Kft. is carrying out the civil engineering works and Azúr Szórakoztatóközpont Kft. is carrying out the work based on the plans of architect Szily Boldizsár .

As a real special feature, due to the immediate proximity to the waterfront, the underground car park levels of the building are being constructed using the so-called „Milan method”. The construction of the underground car park will be completed in two phases.

Unusual solution needed for waterside construction

During the construction of the two-storey underground car park, a 217-metre-long, 65 cm-thick watertight, monolithic diaphragm wall will be built to enclose the work area. A reinforced concrete base slab with a surface area of approximately 2,000 m², supported by diaphragm pillars with point foundations, will form the foundation of the building.

„The work area is bordered by Lake Balaton and its shoreline to the north and east. From a construction point of view, the area is variable and its waterlogged soil is very unfavourable.”

– we learned from the project manager, who emphasised that in order to speed up the construction of the diaphragm wall, instead of temporary ground anchors, the slab above level P2 will be built in advance, contrary to the traditional construction sequence, and will provide the necessary horizontal support for the diaphragm wall as a „Milanese support slab”.

From top to bottom

The „Milan method” technology essentially allows the structure to be supported from above. In Siófok, the reinforced concrete slab above level P2 was constructed before the underground car park was excavated; subsequently, the earth beneath the slab was removed using the underpinning method to support the slab, and then the reinforced concrete base slab was constructed.

This type of civil engineering requires a special work schedule. At our newspaper's request, Ernő Zábrádi outlined the process as follows:

• In Siófok, the first phase of the diaphragm wall construction has been completed, which will ensure the stability of the excavation pit wall during the construction of the basement levels and enable temporary and permanent dewatering. In the finished building, the diaphragm wall absorbs the horizontal earth pressure and transfers it to the basement structures (base slab, P2 and P1 floor slabs), as well as providing support for horizontal loads.
• This is followed by the construction of the P1 basement level as an open excavation pit. In this phase, the deep foundations under the gallery ceiling and the temporary vertical structures supporting the ceiling must be constructed in advance.
• In accordance with the „Milan method”, the P2 support ceiling will then be constructed to support the partition walls with a gallery ceiling in a ring shape.
• Level P2 will thus be constructed as a closed excavation pit: earthworks, installation of the final drainage system, and then, as a final phase, the construction of the nearly 2,000 m² reinforced concrete monolithic base slab and internal support structures can take place, naturally with continuous drainage.

Mining may commence shortly

The construction of the P2 slab built using the Milan method has now been completed, so after the concrete curing time specified by the specialist designers (when the slab reaches the required strength), excavation from under the slab using the underpinning method can begin.

„Currently,” we learned from the project manager, "the final ramp structure providing access to the underground car park is being constructed, which will facilitate earth transport and work processes under the floor slab even during the construction period."