FIELD TESTS ON VIBRATION CREEP OF BASES OF TURBINE FOUNDATIONS, USING A VIBRATING PLATE.

The increase in the capacity of generating units of nuclear and thermoelectric power plants has led to the use of more rigorous requirements on the allowable deformations of turbine units (TU) and, consequently, to the need for studying all the possible causes of increase in the deformation of soil bases under vibrations. When large turbine units are in the operation, their foundations transmit to the soil bases both static and dynamic loads, which may be the cause of long-term, low-attenuation settlement. Observations at different existing installations have shown that settlements of machine foundations with dynamic loads may take place at an attenuated rate over a very long period of time (6 years or more), reaching a significant value (20-60 mm) in the first year. Since the increase in the settlement ceases when the vibration is stopped, this phenomenon has received in the literature the name of 'vibration creep. ' For turbine-unit foundations vibration creep is extremely dangerous because it may lead to impermissible foundation deflections, decentering of the axes, and stoppage of the entire generating unit.