Abstract: Based on the large-distributed silty clay in the impact basin of the lower Yellow River, the dynamic triaxial apparatus and the strain controlled triaxial apparatus were conducted to investigate the undrained shear strength of the silty clay after vibration under different confining pressures and over-consolidated ratios. It is shown that the shear behavior of the sample after vibration is similar to that under over-consolidated state. Compared with the shear behavior before vibration, it can be found that the vibration has little influence on the shear strength when the similar over-consolidated ratio (SOCR) is less than 1.25; while SOCR is larger than 1.25, the shear strength of the sample decreases rapidly and the failure pore pressure ratio decreases firstly and then increases. By comparing the shear strength after unloading under the different SOCR and the same confining pressures, it can be concluded that the shear strength increases with the over-consolidated ratio (OCR) by exponential relation. And the increase of the shear strength caused by SOCR is more obvious than OCR. In addition, the shear strength ratio also increases with the increase of the SOCR and the OCR. Therefore, the OCR can be adopted to evaluate the foundation strength after dynamic load if it is difficult to carry out dynamic test in practice.

Key words: silty clay, vibration loading, over-consolidated ratio, similar over-consolidated ratio, pore pressure, shear strength