Along the time POPP & ASOCIAȚII has used a series of excavation technologies for buildings with multiple underground levels. Each technology has its advantages and disadvantages. That is why the experience accrued within the company has a great deal of saying when choosing the suitable technology for each situation.
For each project POPP & ASOCIAȚII takes into account the existing constraints and pursues to optimize the costs.
For each project, the ground under the neighbouring buildings (when applicable) is carefully checked to see whether its tension state has changed throughout the conduct of the works.
Sometimes, it is necessary to perform excavations deep below the groundwater level. Other times, it is necessary to prevent the uplift of the buildings with fewer levels and which are considerably lighter than the excavated ground. Each case is dealt with separately, taking into account the actual state of things.
Types of excavations:
a. top-down technology:
This is the most reliable solution in terms of impact on the buildings located in its immediate vicinity. The top-down technology is recommended when monument buildings or buildings classified as having RS1 seismic risk are very closely located. This solution is highly recommendable for large-sized basements. The use thereof reduces the infrastructure execution time, which may thus shorten the execution time for the overall structure by concomitantly going forwards with both basement and super-structure.
Unlike the open excavation, this solution may sometimes trigger additional costs but is more time-effective and time is crucial for the most part.
b. open excavation with horizontal shoring:
This type of excavation may be performed by using anchors or struts, both operations being similar in terms of costs.
c. open inclined strut excavations:
This type of solution is used for large-sized enclosures. Most of the time, this method implies the pouring of the foundation in two phases. The downside of using this method is the difficult interaction between the structure building process and the elements of support.
d. jet-grouting method used to underpin foundations and to construct impervious curtains:
In this case, the digging works are protected by supporting walls consisting of jet-grouted vault-shaped piles. An example to this end is the building located in 145 Calea Victoriei.
This technology has been used before by POPP & ASOCIAȚII when sealing diaphragm walls and when executing deep-underpinning works.
Basically, the jet-grouted pile is less expensive than any pile-based solution, however the call-up of the equipment and machinery necessary to make the jet-grouted piles is highly expensive and can be justified only in case of large-scale works.
e. excavations protection by Berlin wall shoring system:
This is a fast running technology and its key advantage is given by the fact that the metal profiles used to support the excavation are recoverable, thus leading to the lowest price spent for excavation shoring for the case of digging works above the underground water level.
This method is sometimes used in narrow enclosures so as to gain a couple of centimetres, however in this case the metal profiles are embedded in the structural system (therefore are no longer recoverable), this solution thus becoming significantly more expensive.
New technologies promoted by POPP & ASOCIAŢII
- Post-tensioning method: used for multi-storey buildings for both infrastructure and super-structure. By using this method the dimensions of the reinforced concrete slabs are reduced, fact that triggers lower execution costs for both individual elements and overall structure. Reducing the size of the slabs and hence the weight of the entire building, directly influences the foundation system, the piles and columns thereof.
For structures with a span of approximately 8 m, the slab execution costs are reduced by 10%. Compared to a conventional solution, this reduction can get to 25-30% for the case of the structures with a span of more than 10 m.
- Technologies for reducing the effects of the seismic action on buildings, by introducing devices intended to absorb and dissipate the energy of seismic and/or wind impact.
These solutions were used in a number of projects coordinated by POPP & ASOCIAȚII, such as: Petrobrazi Refinery, Government Palace, Millenium Center, Cascade project, with a direct and significant impact on both the execution and the operation costs.
- The technology of excavation support by means ofpiles or diaphragm walls sustained by anchors replaces the metal struts or earth berms with anchorage elements. Unlike the struts-based method, the anchorage method is significantly less expensive. Its only downside is that it cannot be used when the length of the anchorage goes beyond the property boundaries and the owner’s approval to this end has not be obtained, or when other buildings with deep basements are located close-by.
- Instead of overlapping joints or welded joints, POPP & ASOCIAŢII currently uses couplings and features for anchoring the reinforcement bars in the beams and columns.
The overlapping method leads to increased consumption of steel and the welded joints infer a large amount of manpower and a long execution term.
- Pre-cast elements: The experience of the engineers of POPP & ASOCIAȚII in designing pre-cast post- and pre-stressed elements enables the facile design of the reinforced concrete structures and metal structures. Our team already has extensive experience in designing mixed structures, irrespective whether they are BAR based structures (structural system using stiff reinforcement concrete) or structures which combine metal, multi-layered wood and concrete.