Osterberg method of testing high capacity bored-piles
It is obvious that for high-rise building construction there should be added additional requirements not only for designing, but also for organization and technology for foundations and underground parts of the building. Only qualitative calculations and entire engineering of geotechnical solutions will let to make really safe construction. As a result of carried out analysis of literature, according to our view, due to appearance of new technologies and types of piles and also new requirements for increase of bearing capacity especially in high-rise building construction, aroused a necessity in application of new pile test methods which will allow setup of high capacity piles. Conducting of tests using hydraulic jacks and division of piles into segments isappropriate for high capacity piles when using standard test methods by vertical load is impossible technically or there is need to use huge anchor constructions, so using such methods is inappropriate economically and technically. The Osterberg cell is very simple mechanically, and made of a metal piston and cylinder that create an expandable chamber holding pressurized oil or water. The pressurized oil acts on the piston, and taking into account that the piston is usually not less 800 mm in diameter, the Osterberg cell can apply relatively large loads for low hydraulic pressures. Loads of more than 2700 t.can be reached with the largest cells. Characteristics of piles after tests with load cells are close to piles, which were not exposed testing, because residual stress in pile is less than the ones, which are left after applying full vertical load in standard tests.