深层液化土层中车站结构地震响应的振动台试验

Shaking Table Tests on the Seismic Response of Station Structures in Deep Liquefied Soils

摘要:

为了探究深层液化土层的液化特点,以名山波、北京饭店波和北京人工波3种地震波为动力荷载,开展振动台试验,通过对比自由场工况和结构工况,分析深层液化土层的液化特点。对土层而言,土层表面无"喷水冒砂"现象,但结构附近土层出现了开裂;自由场工况的孔压比远小于结构工况;北京饭店波引起的孔压比较大,北京人工波次之,名山波最小。对结构而言,北京饭店波引起的结构加速度与结构拉应变增量最大,北京人工波次之,名山波最小。深层液化土层的液化行为主要受上覆荷载和地震波频率特性的影响,上覆荷载越大,深层液化土层的液化程度越小;地震波主频越高,深层液化土层的液化程度越小。车站结构的地震响应与地震波主频高低关系密切。

Abstract:

To investigate liquefaction behavior in deep liquefied soil layers, this paper performed shaking table tests using three seismic waves, i.e., the Ming Shan wave, Beijing Hotel wave and Beijing artificial wave, as the dynamic loads. By comparing free-field and structural conditions, the liquefaction characteristics of deep liquefied soil layers were analyzed. For the soil layer, no water spraying and sand bubbling occurred on the surface, but cracking developed near the structure. The pore-pressure ratio in the free-field condition was much smaller than that in the structural condition. The pore-pressure ratio induced by the Beijing Hotel wave was the largest, followed by that induced by the Beijing artificial wave and then the Ming Shan wave. For the structure, the Beijing Hotel wave produced the largest structural acceleration and the greatest increase in tensile strain, followed by the Beijing artificial wave and then the Ming Shan wave. These results indicate that liquefaction of deep liquefied soil layers is mainly controlled by overburden stress and the frequency content of the seismic wave: larger overburden load and higher dominant seismic frequency both reduce the degree of liquefaction. The seismic response of the station structure correlates closely with the dominant seismic frequency.