Determination dynamic behavior of clays

For the safety of the structure to be built on the soil, soil's properties should be well known. It is necessary to know the stress-deformation properties of the ground in order to model the soil of the soils under dynamic loads. These parameters are very important in terms of modeling of earthquake resistant structure designs. In this study, behavioral changes in clay soils under dynamic loads were investigated. For this purpose, resonant column (RC) and torsional shear (TS) tests were performed on clay soil samples with different silt percentages. Samples which's overconsolidation ratio (OCR) 1 and 2, were subjected to resonant column test up to 1% shear deformation and then torsional shear test up to 2.5% shear deformation. As a result, it was observed that with the increase of the confining pressure, the shear modulus of the clay soil increased and the damping rate decreased. The decrease of silt ratio in the clay soil resulted a decrease on the shear modulus and damping ratio. Also an increase was observed in the normalized shear modulus curve. In addition, with the decrease of the silt ratio in the clay soil, a decrease was observed at the water pore pressure. In OCR 1 and 2 samples, with the increase of OCR, shear modulus increased and damping ratio decreased and pore water pressures decreased with increase of OCR. In the samples which subjected to 3 cyclic RC test, shear modulus decreased and damping ratio increased with the increase of cyclic number. The highest reduction of shear modulus was observed in the most silty samples. Higher pore water pressures were observed in the samples subjected to 3 RC test compared to the 1 RC test. In experiments conducted using 0.5Hz and 1Hz frequencies in TS, no significant changes were observed in the shear modulus and normalized shear modulus curves with the increase of frequency. However, the damping ratio increased slightly with the increase of frequency. In the TS test, it was observed that there was a decrease in the pore water pressures with the increase of the frequency.