NEW TECHNOLOGIES OF UNDERGROUND CONSTRUCTION OF REINFORCED CONCRETE
It is possible to allocate three major areas related to the development of underground space of the metropolis: the laying of transport and communication tunnels for the creation of infrastructure; the construction of a separate underground constructions and structures to create recreational spaces; construction of an underground multi floors, including high-rise buildings and complexes.
Complex hydrogeological conditions and the specifics of the production of works in the dense buildings of the city centre and require a durable materials and reliable construction solutions, and new technologies. Materials concrete and reinforced concrete have a certain advantage for underground construction. The disadvantages of reinforced concrete underground structures are monolithic joints between prefabricated elements; numerous technological joints in a monolithic base plate and walls of the underground part of the building; cross-cutting vertical expansion joints between acting in terms of the underground part of the building and high-rise; high cost and effort of waterproofing, drainage layer and protective masonry; repair leaks waterproofing technology and especially along vertical joints; the saturation of the armature base plates high-rise buildings, especially high-rise buildings and the difficulty of their casting, especially in places bypass rods.
For the past 15 years the specialists of NIIZHB, and took an active part in the process of building unique structures in Moscow, transport and communications tunnels in Lefortovo and under B. Dmitrovka str.; shopping and recreation complex “Okhotny Ryad” and monolithic slab Foundation under high-rise part of the Central core of the MIBC, an underground garages and construction of a zero cycle of buildings in a Standby fare in Moscow and the administrative building of the school in the Istra district and many other objects. In the course of work the following tasks were solved:
• receive team and monolitspetsstroy lining of tunnels of high-strength and dense concrete with a low setting temperature and a high cracking resistance;
• strengthen the bases and prevent filtration of groundwater by creating seepage curtain of walls and baraccuda piles with the use of special, not washable with water of concrete mixtures, not exfoliating when laying in a watery environment (the well);
• continuous concreting batches up to 15 thousand m3 and the provision of thermal crack resistance of structures;
• ensuring the water tightness of the contour of the walls of structures without gluing, coating and other waterproofing through the use of concrete with compensated shrinkage and reliable construction solutions;
• combating techmi produced in violation of technological regulations of production of works for laying of concrete and reinforcement.
These problems have been solved and implemented in the sites in Moscow in the absence of existing regulations in construction.
2. Providing thermal crack resistance and water resistance solid foundations with continuous concrete self-compacting mixtures
Increase the scale of construction of high-rise and high-rise buildings requires the problem of providing thermal crack resistance of massive monolithic slabs, constructed in conditions of both positive and negative temperatures by the method of continuous concreting.
Traditional experience of solving this problem was to split the design into separate blocks (hook) cast discretely, i.e. with breaks and the formation of technological joints. In NIIZHB developed and tested the technology of erection of massive structures of base plates up to 14 thousand m3, without division into separate blocks with continuous walls of heavy concrete. The essence of the technology consists in application of modified concretes with low setting temperature classes up to 60, prepared from high-mobility, including self-compacting mixtures. A concrete mix with a slump of 28 cm have a high fluidity (a melt of a cone not less than 65 cm), the coherence-proslaivaet (the magnitude of dehydration is not over 0,3%), contain Portland cement in an amount of not more than 330 kg/m3, of organic multicomponent modifier MB-01, including silica fume (MK), superplasticizer and the hardening regulator. It predetermines high Adebola-Divemaster mixtures and reduce the cost of concrete structures is low, heat dissipation and cost reduction in the care and aging of concrete structures. As a result, the effectiveness of the technology is manifested in the reduction of terms of erection of structures.
Since mikrokremnezema – an expensive and scarce material, we have developed new types of organic-mineral modifiers of MB-30C, MB-50, MB-100C, in which MK is replaced by fly ash, respectively at 30, 50, and 90%.
The positive experience obtained during the concreting p lit volume 9.5 and 14 thousand m3 of concrete of classes B40-60 in the construction of complex “Federation” in the MIBC “Moscow-city”.
3. The use of expanding additives in the concrete for the abolition of waterproofing in the construction of the underground part of high-rise buildings and complexes
One of the most effective materials for the construction of underground parts of buildings is concrete with compensated shrinkage.