第36卷第1期 北京科技大学学报 Vol.36 No.1 2014年1月 Journal of University of Science and Technology Beijing Jan.2014 冻土覆盖下液化场地桩基地震响应的振动台试验研究 杨润林)，乔春明”，ZHANG Xiao-yu2,YANG Zhao-hui 1)北京科技大学土木与环境工程学院，北京1000832)阿拉斯加安克雷奇大学工学院，安克雷奇99508，美国 ☒通信作者，E-mail:rlyang(@usth.edu.cm 摘要利用振动台进行了在地震激励下冻土、可液化砂土与钢管桩之间的相互作用模拟试验研究.试验设计柔性模型箱装 填土体以模拟边界影响，通过配比试验制备混凝土砂浆模拟上覆冻土层，采用饱和砂土作为液化土，利用顶部附加集中质量 的方法模拟钢管桩的惯性荷载.试验过程中选取调幅地震波模拟地震激励，通过实时测量桩的应变、桩/冻土位移和砂土内的 孔隙水压力等方面的数据，分析冻土层覆盖下砂土的液化情况和与之对应的桩基动力反应情况.试验结果显示：在地基液化 发生前，冻土层可以给桩基提供一定的侧向约束，有利于提高其承载力并抑制其侧向变形：然而一旦出现液化，冻土层则可能 增强地基液化的趋势，导致桩基承载性能下降. 关键词桩基；冻土；液化：地震响应：振动台测试 分类号TU475 Shaking table test study on seismic responses of pile foundations embedded in liquefiable ground with the frozen crust YANG Run--in》a,QlA0 Chun-ming',ZHANG Xiao-→u》，YANG Zhao--hui2 1)School of Civil and Environmental Engineering,University of Science and Technology Beijing,Beijing 100083,China 2)School of Engineering,University of Alaska Anchorage,Anchorage 99508.USA Corresponding author,E-mail:rlyang@ustb.edu.cn ABSTRACT The seismic responses of a single steel-pipe pile built in the frozen crust and the liquefiable sand soil were studied by shaking table tests.A flexible soil container was designed and used to construct the soil profile in order to minimize the boundary effect.The frozen crust was simulated through the mortar which was made of cement,sand and water by the mixture ratio.Liquefaction can occur in the saturated sand soil beneath the frozen crust.A lumped mass was exerted at the top of the pile to satisfy the inertia con- ditions.During the tests,several amplitude-scaled ground motions were chosen as input seismic waves.The liquefying levels of the sat- urated sand soil and the dynamic responses of the pile can be analyzed via the measured real-time data including strains of the pile,dis- placements between the pile and the frozen crust and pore water pressures in the sand.Experimental results show that before liquefac- tion occurs,the frozen crust can provide a lateral constraint,and thus improve the load bearing capacity of the pile and suppress its lat- eral deformation.It is also found that once liquefaction occurs,the frozen crust may further strengthen this tendency and deteriorate the performance of the pile. KEY WORDS piles:frozen soils;liquefaction:seismic response;shaking table test 由于桩基可以避免地表温度条件改变可能对地 台模拟地震激励试验，Yao等回研究了地基液化时 基变形和承载力带来的不利影响，有效维系上部结 桩一土一上部结构系统的瞬时相互作用以及力学建 构的稳定性，因此在冻土场地中被广泛应用.地基 模问题：He等同和Haei等司分别研究了地基液化 液化对桩基的地震承载力有显著影响，一直是桩基 后土体侧向流动诱发的单桩或群桩的地震响应； 工程中需要重点考虑研究的课题之一山.通过振动 Tang等研究了在砂土液化情况下桥墩及其下设 收稿日期：2012-11-20 基金项目：中美合作研究项目(AUTC料10015) DOI:10.13374/j.issn1001-053x.2014.01.020:http://journals.ustb.edu.cn第 36 卷 第 1 期 2014 年 1 月 北京科技大学学报 Journal of University of Science and Technology Beijing Vol． 36 No． 1 Jan． 2014 冻土覆盖下液化场地桩基地震响应的振动台试验研究 杨润林1) ，乔春明1) ，ZHANG Xiao-yu 2) ，YANG Zhao-hui 2) 1) 北京科技大学土木与环境工程学院，北京 100083 2) 阿拉斯加安克雷奇大学工学院，安克雷奇 99508，美国  通信作者，E-mail: rlyang@ ustb． edu． cn 摘 要 利用振动台进行了在地震激励下冻土、可液化砂土与钢管桩之间的相互作用模拟试验研究． 试验设计柔性模型箱装 填土体以模拟边界影响，通过配比试验制备混凝土砂浆模拟上覆冻土层，采用饱和砂土作为液化土，利用顶部附加集中质量 的方法模拟钢管桩的惯性荷载． 试验过程中选取调幅地震波模拟地震激励，通过实时测量桩的应变、桩/冻土位移和砂土内的 孔隙水压力等方面的数据，分析冻土层覆盖下砂土的液化情况和与之对应的桩基动力反应情况． 试验结果显示: 在地基液化 发生前，冻土层可以给桩基提供一定的侧向约束，有利于提高其承载力并抑制其侧向变形; 然而一旦出现液化，冻土层则可能 增强地基液化的趋势，导致桩基承载性能下降． 关键词 桩基; 冻土; 液化; 地震响应; 振动台测试 分类号 TU475 Shaking table test study on seismic responses of pile foundations embedded in liquefiable ground with the frozen crust YANG Ｒun-lin1)  ，QIAO Chun-ming1) ，ZHANG Xiao-yu2) ，YANG Zhao-hui 2) 1) School of Civil and Environmental Engineering，University of Science and Technology Beijing，Beijing 100083，China 2) School of Engineering，University of Alaska Anchorage，Anchorage 99508，USA  Corresponding author，E-mail: rlyang@ ustb． edu． cn ABSTＲACT The seismic responses of a single steel-pipe pile built in the frozen crust and the liquefiable sand soil were studied by shaking table tests． A flexible soil container was designed and used to construct the soil profile in order to minimize the boundary effect． The frozen crust was simulated through the mortar which was made of cement，sand and water by the mixture ratio． Liquefaction can occur in the saturated sand soil beneath the frozen crust． A lumped mass was exerted at the top of the pile to satisfy the inertia con￾ditions． During the tests，several amplitude-scaled ground motions were chosen as input seismic waves． The liquefying levels of the sat￾urated sand soil and the dynamic responses of the pile can be analyzed via the measured real-time data including strains of the pile，dis￾placements between the pile and the frozen crust and pore water pressures in the sand． Experimental results show that before liquefac￾tion occurs，the frozen crust can provide a lateral constraint，and thus improve the load bearing capacity of the pile and suppress its lat￾eral deformation． It is also found that once liquefaction occurs，the frozen crust may further strengthen this tendency and deteriorate the performance of the pile． KEY WOＲDS piles; frozen soils; liquefaction; seismic response; shaking table test 收稿日期: 2012--11--20 基金项目: 中美合作研究项目( AUTC#410015) DOI: 10． 13374 /j． issn1001--053x． 2014． 01． 020; http: / /journals． ustb． edu． cn 由于桩基可以避免地表温度条件改变可能对地 基变形和承载力带来的不利影响，有效维系上部结 构的稳定性，因此在冻土场地中被广泛应用． 地基 液化对桩基的地震承载力有显著影响，一直是桩基 工程中需要重点考虑研究的课题之一［1］． 通过振动 台模拟地震激励试验，Yao 等［2］研究了地基液化时 桩--土--上部结构系统的瞬时相互作用以及力学建 模问题; He 等［3］和 Haeri 等［4］分别研究了地基液化 后土体侧向流动诱发的单桩或群桩的地震响应; Tang 等［5］研究了在砂土液化情况下桥墩及其下设