循环荷载下液化对土层水平往返变形的影响
|
摘要
采用多工况振动台实验研究液化对土层水平往返变形的影响。以干砂实验为参照,分析孔压增长与土层加速度和土层往返变形之间的关系。结果表明:液化将引起土表加速度显著降低,减小惯性力传递,但同时会引起土层往返剪应变明显增大。对往返变形而言,液化土层往返剪应变就可达到1%~5%的大变形状态,且液化土层往返剪应变沿深度呈下大上小分布。土层中孔压比0.4~0.8是往返变形出现放大的敏感段,在孔压比0.8左右而不是在1.0达到最大。作为其结果,土层液化将对刚性上部结构振动起减震作用,但同时增大的往返剪应变也易导致基础和地下结构破坏,特别是对液化层与下部非液化层交界处的构件更敏感。
The effects of liquefaction on cyclic deformation of soil layers are investigated by shaking table tests.Taken the dry sand tests as a consult,the relations between the pore water pressure increasing and the accelerations and deformation of the soil layer are presented.The results show that the liquefaction greatly reduces the acceleration amplitude and inertia force of surface ground,meanwhile however,the cyclic deformations of the soil layer increase significantly.The cyclic shear strain in liquefied soil layers can reach 1%~5% and the strain in the upper layer is less than that in the sub layer.The sensitive range for obvious change of the cyclic deformation appears when the water pressure ratio is about in 0.4~0.8 and reaches the maximum when is about 0.8 rather than 1.0.As a result,the liquefied soil layer reduces the vibration of the rigid superstructure,but the increasing cyclic deformation due to liquefaction can easily destroy the foundation and underground structures,especially for the part of the foundation and underground structures near the interface between the liquefied layer and non-liquefied soil layer.
The effects of liquefaction on cyclic deformation of soil layers are investigated by shaking table tests.Taken the dry sand tests as a consult,the relations between the pore water pressure increasing and the accelerations and deformation of the soil layer are presented.The results show that the liquefaction greatly reduces the acceleration amplitude and inertia force of surface ground,meanwhile however,the cyclic deformations of the soil layer increase significantly.The cyclic shear strain in liquefied soil layers can reach 1%~5% and the strain in the upper layer is less than that in the sub layer.The sensitive range for obvious change of the cyclic deformation appears when the water pressure ratio is about in 0.4~0.8 and reaches the maximum when is about 0.8 rather than 1.0.As a result,the liquefied soil layer reduces the vibration of the rigid superstructure,but the increasing cyclic deformation due to liquefaction can easily destroy the foundation and underground structures,especially for the part of the foundation and underground structures near the interface between the liquefied layer and non-liquefied soil layer.
引文
[1]廖胜修,程菊红.黄土场地震动液化实例[J].西北地震学报,2007,29(1):63-65.
[2]刘红玫,袁中夏,王峻.基于内时理论的饱和黄土孔压增长模型的试验研究[J].西北地震学报,2004,26(4):272-274.
[3]张建民.地震液化后地基侧向变形对桩基础的影响[A]∥第八届土力学及岩土工程学术会议论文集[C].北京:万国学术出版社,1999.
[4]刘汉龙.地震液化区分布范围对地面大位移的影响[J].河海大学学学报,2001,29(5):1-6.
[5]李学宁,刘惠珊,周根寿.液化层减震机理研究[J].地震工程与工程振动,1992,12(2):84-91.
[6]苏栋,李相菘.砂土自由场地震响应的离心机试验研究[J].地震工程与工程振动,2006,26(2):166-170.
[2]刘红玫,袁中夏,王峻.基于内时理论的饱和黄土孔压增长模型的试验研究[J].西北地震学报,2004,26(4):272-274.
[3]张建民.地震液化后地基侧向变形对桩基础的影响[A]∥第八届土力学及岩土工程学术会议论文集[C].北京:万国学术出版社,1999.
[4]刘汉龙.地震液化区分布范围对地面大位移的影响[J].河海大学学学报,2001,29(5):1-6.
[5]李学宁,刘惠珊,周根寿.液化层减震机理研究[J].地震工程与工程振动,1992,12(2):84-91.
[6]苏栋,李相菘.砂土自由场地震响应的离心机试验研究[J].地震工程与工程振动,2006,26(2):166-170.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心