摘要
针对地震时处于可液化土层中的盾构隧道易发生上浮的现象,为了探究上浮发生条件,通过有限差分模型与振动台试验相结合的方式探讨其上浮位移模式。基于有限差分软件FLAC3D建立地震动力液化分析模型,采用可以反映地震荷载作用下孔压增长的Finn液化本构模型,以超静孔压比为评价指标,通过振动台试验验证分析模型的可靠性;对数值模型设置不同的组合工况,分析标准贯入击数、隧道埋深对隧道上浮位移的影响,探究因地震导致隧道上浮的位移模式,即地震动剪切变形引起的隧道上浮位移和土层液化引起的隧道上浮位移,前者与隧道埋深有关,后者主要与土质条件(标准贯入击数)有关,分别得到两者的关系曲线;通过受力分析及公式推导得到隧道上浮临界超静孔压比,并与数值计算结果相互验证,得到判断地震液化引起隧道上浮的方法。研究结果表明:标准贯入击数越小、隧道埋深越小,则隧道上浮位移越大;地震液化引起隧道上浮的临界条件为隧道所受到的浮力大于隧道自重与隧道上覆土有效压力之和,可通过标准贯入击数或超静孔压比与隧道埋深的关系进行判断,如7°设防烈度下直径6.2 m埋深为10 m地下水位1 m的盾构隧道,标准贯入击数需小于7或超静孔压比需大于0.432才会发生由地基液化引起的上浮位移;该方法可为隧道抗震设计提供参考。
Aiming at the uplifting behavior of shield tunnel in liquefiable soil strata during earthquake,to explore the uplifting conditions,the uplift mode was discussed by combining finite difference model with shaking table test.Based on the finite difference software FLAC3D,an analysis model of seismic dynamic liquefaction was established.The Finn liquefaction constitutive model which can reflect the increase of pore pressure under seismic load was adopted.The reliability of the analysis model was verified by shaking table test with the excess pore pressure ratio as the evaluation index.Different combination cases were set for the numerical model calculation.The influence of standard penetration test-blow counts(SPT-blow counts)and tunnel buried depth on the tunnel uplift was analyzed.The uplift mode of tunnel caused by earthquake was further explored.The relationship curves of the two were obtained respectively.Through force analysis and formula derivation,the critical excess pore pressure ratio of tunnel uplifting was obtained,which was mutually confirmed with the numerical calculation results.The method of judging tunnel uplifting caused by seismic liquefaction was obtained.The results show that the smaller SPT-blow counts and tunnel depth are,the larger the uplift is.The uplift is divided into two parts,one caused by seismic shear deformation and the other by soil liquefaction.The former is related to the buried depth of the tunnel,and the latter is influenced by the soil condition(SPT-blow counts).The critical condition of tunnel uplifting caused by seismic liquefaction is that the buoyancy of the tunnel needs to be greater than the sum of the self-weight of the tunnel and the effective pressure of the overlying soil,which can be judged by the relationship between SPT-blow counts or the excess pore pressure ratio and the buried depth of the tunnel.For example,for a shield tunnel with diameter of 6.2 m,buried depth of 10 m and groundwater level of 1 m under the fortification intensity of 7 degree,the uplift caused by soil liquefaction occurs when SPT-blow counts is less than 7 or the excess pore pressure ratio is greater than 0.432.This method can provide reference for tunnel aseismic design.7 tabs,16 figs,26 refs.
作者
钟小春
易斌斌
竺维彬
祝思然
罗淑仪
王奇
ZHONG Xiao-chun;YI Bin-bin;ZHU Wei-bin;ZHU Si-ran;LUO Shu-yi;WANG Qi(College of Civil and Transportation Engineering,Hohai University,Nanjing 210098,Jiangsu,China;Guangzhou Metro Group Co.Ltd.,Guangzhou 510220,Guangdong,China;Guangzhou Mass Transit Engineering Consultant Co.Ltd.,Guangzhou 510030,Guangdong,China)
出处
《长安大学学报（自然科学版）》
CAS
CSCD
北大核心
2024年第1期80-90,共11页
Journal of Chang’an University(Natural Science Edition)
基金
国家自然科学基金项目(52178387,51678217)。
关键词
隧道工程
盾构隧道
地震液化
隧道上浮
上浮模式
数值模拟
tunnel engineering
shield tunnel
seismic liquefaction
tunnel uplifting
uplift mode
numerical simulation
