Experimental study on properties of seismic loading and their influence on seismic compression in sands
The structure of a dynamic simple shear strain test system which is the latest generation of GCTS made in USA as well as its features is presented. The input method for primarily real seismic loading is analyzed. And the validity of the method is verified. Based on the US Filter clean sand, the preparation process of the sand samples is explained. Two shock types of seismic waves and two vibration types of seismic waves are selected for input loading in tests. Considering the relative density and overlying loading, the test conditions are planned, and 202 dynamic simple shear tests controlled by strain are carried out. The test results show that the seismic compression in sands due to the vibration-type seismic waves is larger than that induced by the shock-type seismic waves under the same relative density of sands and the same overlying loading. The seismic compression is mainly caused by several seismic waves with relatively high peak prior to the maximum peak. And the maximum vertical shear strains in sands are corresponding to the maximum peak seismic waves. For the seismic waves after the maximum peak, the waves whose peak reaches 80% of the maximum peak approximately in the seismic waves have more significant effectiveness on deformations of sands. For the shock-type seismic waves, various waves after the maximum peak have no obvious effect on deformations of sands. However, for the vibration-type seismic waves, the seismic compressions in sands are determined by the waves both prior to the maximum peak and that in a certain range after the maximum peak together.