液化砂土地基刚度恢复过程的振动台试验

地震来临时,饱和砂土地基在强烈的地面运动作用下可能发生液化现象,导致土体散失刚度和承载能力;另一方面,当地震停止后,伴随着超孔隙水压的消散和有效应力的增加,地基的刚度又会逐渐恢复。本文针对液化地基的刚度恢复过程进行了振动台试验研究。首先通过振动加载使砂土地基液化,然后在振动停止后通过锤击振动台底板在地基内部产生剪切波,并通过测量剪切波速的变化获得土体剪切模量的变化过程。试验结果表明,地基内部的刚度恢复过程与超孔隙水压的消散过程及有效应力的增长过程完全同步,并且剪切模量的增长与有效应力的增加呈现良好线性关系。本研究利用相同的输入波对同一地基进行了三次连续加载,发现随着加载次数的增加,模型地基液化后的刚度恢复过程也逐步加快。

Shaking-table tests on the stiffness recovery process of liquefied sandy ground

During earthquake, saturated sandy ground maybe liquefied and lose its stiffness for supporting structures. On the other hand, after the stop of earthquake, the ground will regain its stiffness accompanying with the dissipation of excess pore water pressure and the increase of effective stress. This paper presents an experimental study on the stiffness recovery process of liquefied sandy ground by using of shaking table. First, shaking loads were applied to a model sandy ground to give rise of liquefaction; then after the stop of shaking stopped, the shear-wave speed propagating through the ground was measured to obtain its shear modulus. The same input motion was applied to the model ground three times in succession. The test results demonstrated that the stiffness recovery process is completely in the same pace with the dissipation of excess pore water pressure, and the shear modulus increases almost linearly with the increase of effective stress. It was also found that the ground that experienced liquefaction more and more times will recovery its stiffness more and more quickly after liquefaction.