冻土层覆盖条件下砂土地震液化特性振动台试验研究  

Study on shaking table test about seismic liquefaction characteristics of sandy soil covered with frozen soil layer

作　　者：秦子涵 张熙胤[1] 吕旭浩 朱奎源 罗乾 左森虎 QIN Zihan;ZHANG Xiyin;LÜXuhao;ZHU Kuiyuan;LUO Qian;ZUO Senhu(School of Civil Engineering,Lanzhou Jiaotong University,Lanzhou 730070,China)

机构地区：[1]兰州交通大学土木工程学院,甘肃兰州730000

出　　处：《冰川冻土》2024年第6期1849-1859,共11页Journal of Glaciology and Geocryology

基　　金：国家自然科学基金项目(52068045);陇原青年创新创业人才(团队)项目资助。

摘　　要：冻土区地震液化现象频发,上覆盖土层的冻结将砂土地震液化特性分析变得复杂化。为研究上覆冻土层对砂土地震液化特性的影响,设计了具有土体冻结系统的剪切模型箱,开展冻土层覆盖条件下砂土地震液化振动台试验,分析不同地震波作用下模型土体加速度、孔隙水压力、土压力、层间和顶部位移的变化规律。结果表明,冻土层覆盖条件下砂土层从底部开始出现局部液化现象,随输入地震动峰值的增大,其液化高度逐渐增加。砂土层液化后的加速度放大系数变化规律与冻土层保持一致,均随着输入地震动峰值的增大先增加后降低,但砂土层对输入地震波的放大能力大于冻土层,不同土层对地震动放大的敏感程度不同。此外,冻土层出现震陷和滑移现象,地震液化造成水分上迁汇聚在冻土-砂交界处,致使冻土层滑移加剧,砂土层的层间位移会随土层高度的增加而增大,但在液化面高度以上发生突降。因此,上覆冻土层可液化场地中结构的抗震验算需重点关注冻土-砂交界处以及液化高度处。本文可为上覆冻土层的可液化场地中土体力学行为变化研究提供数据支撑。Earthquake-induced liquefaction occurs frequently in frozen soil regions.Taking the earthquake records in China as an example,the earthquake in Bachu County,Xinjiang in 2003,the M_s7.1 earthquake in Yushu,Qinghai in 2010,the M_w6.6 Akto earthquake in the northwest Pamir Plateau in 2016,and the Menyuan6.9 earthquake in Qinghai in 2022 all showed seismic liquefaction.At the same time,there are 5~10 m thick silt soil layer,fine sandy soil layer,medium-coarse sandy soil layer and other soil layers in the alluvial areas in the eastern part of the river valley around the Qinghai-Xizang Plateau and some debris flow accumulation areas in the middle and western ends of the Qinghai-Xizang Plateau.The perennial saturated area is also in the high-incidence area of earthquakes,and the possibility of liquefaction damage is extremely high,which needs urgent attention from researchers.The influence of overlying frozen soil on sand liquefaction characteristics is complex.The soil temperature,moisture content,confining pressure,loading frequency and the coupling of various factors will affect the dynamic performance of frozen soil.Freeze-thaw cycles,the content and type of fine-grained sand,poor drainage before freezing and other factors will affect the liquefaction resistance of sandy soil.In order to study the seismic liquefaction characteristics of sandy soil covered with frozen soil layer and clarify the variation law of dynamic parameters of frozen soil and sandy soil under different seismic waves,a shear model box of soil freezing system was designed and shaking table test of seismic liquefaction characteristics of sandy soil covered by frozen soil layer was carried out.The variation of acceleration,pore water pressure,soil pressure,interlayer and top displacement of the model under different seismic waves was analyzed.The results show that under the condition of frozen soil coverage,the sandy soil layer will begin to liquefy locally from the bottom,and the liquefaction height will gradually increase with the increase of the

关 键 词：冻土层 砂土液化 振动台试验 地震响应 

分 类 号：TU435[建筑科学—岩土工程]