CDR REPORT

CDR report



CDR report

Project 1 - Construction of Residental building

In recent years, piled foundations have received wide application in the construction of residential buildings. In Ryazan', Ufa, Omsk, and several other cities, nearly 90% of the residential buildings are being erected on piled foundations. In Moscow, residential buildings constructed on piled foundations in 1974 amounted to 47% of the total. The total volume of pile usage in residential building, according to our calculations, currently amounts to nearly 3.5 million m 3 annually, and the proportion of piled foundations in the whole country averages 32%. A rational application of piled foundations permits significant reductions in the volumes of earthen and concrete works, raises the level of industrialization of zero-cycle works, cuts the construction periods and costs of foundations, permits the carrying out of works at any time of the year, and improves the safely of buildings and structures in service. However, these advantages are not always realized in the current practice of piled foundation engIneering. Experience in the field of residential building construction shows that there are cases of irrational installation of piled foundations, as the result of an uncritical attitude to the recommendations of individual authors in regard to the areas of efficient pile application and a failure to allow for definite construction conditions (soil properties, cost levels, etc.). It was not by sheer accident that some constructional organizations, including those in Moscow, substituted strip footings for piled foundations, e.g., apartment blocks Nos. 5 and 9 in mini-development 8 of Teplyi Stan, several structures in mini-developments 8-b and 8-c of Orekhovo-Borisovo, Zelenograd, et al.). The wide-spread introduction of piled foundations for residential buildings was not preceded by complex engineering-economic considerations.

In the initially constructed works, the types of foundations examined were, as a rule, for buildings without a basement and without a technical-services cellar (piled foundations without excavation). In many cases, strip footings were compared with piled foundations employing short piles 4 to 6 m long, for conditions where the horizon of the supporting soil layer is located at a shallow depth. The adopted basis for comparison were uneconomic designs of strip footings consisting of precast standard blocks of solid section. In making engineering-economic evaluations of piled foundations, the conditions for comparability of design solutions were not always observed. Thus, for instance, the dimensions of the technical-services cellar of buildings were assumed to be less for piled foundations than those for the strip-footing type [I]. Therefore, a reduction in the volume of earthen 'and concrete works was achieved, not only by the substitution of piled foundations for common types, but also by worsening the service conditions of the sewerage-engineerIng facilities of the building (Fig. i).

Recommendations for the wholesale application of piled foundations in ordinary ground conditions also, were based on similar engineering-economic considerations.* These recommendations were incorporated in a series of standard codes, including "Handbook for Design of Piled Foundations" [2], which noted the expediency of using piled foundations instead of strip footings where the laying depth of ...