液化地基自由场振动台模型试验研究
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摘要
进行了液化场地自由场振动台试验,试验采用柔性容器以减小边界影响,采用上覆黏土层的饱和砂土作为模型土。试验中再现了液化场地土的震害现象。得出的主要规律有:随着振次的增加,地基的频率迅速降低,阻尼比迅速增大;砂土对地震动起滤波作用;土体的加速度峰值反应在高度上呈"K"形分布;当最初加速度峰值到达前,砂土层中的孔压比存在负值;震后土中振动孔隙水压力不一定随振动的停止而立即开始消散,在短期内可能继续增长。
Shaking table model tests on the free field considering the soil liquefaction are described in this paper.A flexible container is fabricated to minimize the box effect.Saturated sand soil is employed as model soil.In the tests,macro-phenomena of soil liquefaction due to natural earthquake are reproduced well,such as sand boiling,water spouting and soil surface sinking.Some important findings from the present tests are as follows.The natural frequency of soil decreases and the damping ratio of soil increases with the increase of the shaking.The liquefied soil can filter the vibration. The response of the acceleration amplitude is in K shape along the height.The phenomena of the transient minus pore pressure occurred in the test.Pore water pressure does not always dissipate in short time immediately after the excitations,but it may keep on increasing too.
Shaking table model tests on the free field considering the soil liquefaction are described in this paper.A flexible container is fabricated to minimize the box effect.Saturated sand soil is employed as model soil.In the tests,macro-phenomena of soil liquefaction due to natural earthquake are reproduced well,such as sand boiling,water spouting and soil surface sinking.Some important findings from the present tests are as follows.The natural frequency of soil decreases and the damping ratio of soil increases with the increase of the shaking.The liquefied soil can filter the vibration. The response of the acceleration amplitude is in K shape along the height.The phenomena of the transient minus pore pressure occurred in the test.Pore water pressure does not always dissipate in short time immediately after the excitations,but it may keep on increasing too.
引文
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[2]Tamura S,Suzuki Y,Tsuchiya T,et al.Dynamic response and failure mechanisms of a pile foundation during soil liquefaction by shaking tabletest with a large-scale laminar shear box[C]//12th World Conference on Earthquake Engineering,Auckland,New Zealand,2000:0903.
[3]Kagawa T,Minowa C,Abe A.EDUS project(earthquake damage to underground structures)[C]//12th World Conference on EarthquakeEngineering,Auckland,New Zealand,2000:0329.
[4]陈跃庆,吕西林,侯建国,等.有建筑物存在的软土地基液化模拟地震振动台试验研究[J].武汉大学学报:工学版,2003,36(1):59-64.
[5]凌贤长,郭明珠,王东升,等.液化场地桩基桥梁震害响应大型振动台模型试验研究[J].岩土力学,2006,27(1):7-11.
[6]孟上九,刘汉龙,袁晓铭,等.可液化地基上建筑物不均匀震陷机制的振动台试验研究[J].岩石力学与工程学报,2005,24(11):1978-1985.
[7]冯士伦,王建华,郭金童.液化土层中桩基抗震性能振动台试验研究[J].土木工程学报,2005,38(7):92-95.
[8]陈跃庆,吕西林,李培振,等.分层土-基础-高层框架结构相互作用体系振动台模型试验研究[J].地震工程与工程振动,2001,21(3):104-112.
[9]Lu X L,Li P Z,Chen B,et al.Computer simulation of the dynamic layered soil-pile-structure interaction system[J].Canadian GeotechnicalJournal,2005,42(3):742-751.
[10]徐志英,施善云.土与地下结构动力相互作用的大型振动台试验与计算[J].岩土工程学报,1993,15(4):1-7.
[11]陈文化,门福录,景立平,等.有建筑物存在的饱和砂土地基液化振动台模拟实验研究[J].地震工程与工程振动,1998,18(4):54-59.
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