地震荷载特征及其对砂土震陷影响试验研究

介绍美国最新一代动循环单剪系统的组成及其特点,分析原始真实地震荷载的输入方法,并对真实地震荷载的输入有效性进行验证。以美国Filter净砂为对象,选择冲击型与振动型地震波作为试验输入荷载,考虑砂土相对密度、上覆荷载,设计不同试验工况研究地震荷载特征及其对砂土震陷的影响,共计试验组数202组。试验结果表明：在同一砂土相对密度和上覆荷载条件下,振幅相同的振动型地震波引起的砂土震陷比冲击型地震波引起的砂土震陷大;砂土震陷主要由最大地震荷载峰值之前的各个较大峰值的地震波引起,其中最大峰值对应的地震波引起的砂土竖向应变最大;对于最大峰值之后的地震波,其峰值应达到该地震波最大峰值的80%左右才对砂土变形具有较明显的贡献作用;冲击型地震波最大峰值之后的各地震波对砂土变形影响不明显;对于振动型地震波,其最大峰值之前及最大峰值之后一定范围内的地震波作用共同决定着砂土变形的大小。

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.