间歇性循环荷载条件下饱和重塑黏土的动力特性试验  

Experiment of Dynamic Characteristics of Saturated Remolded Clay Under Intermittent Cyclic Loading

作　　者：雷华阳[1,2,3] 杨晓楠 许英刚 张磊 Lei Huayang;Yang Xiaonan;Xu Yinggang;Zhang Lei(School of Civil Engineering,Tianjin University,Tianjin 300350,China;Binhai Key Laboratory of Civil Engineering Structure and Safety,Ministry of Education,Tianjin 300350,China;Key Laboratory of Earthquake Engineering Simulation and Seismic Resilience,CEA,Tianjin 300350,China)

机构地区：[1]天津大学建筑工程学院,天津300350 [2]滨海土木工程结构与安全教育部重点实验室,天津300350 [3]中国地震局地震工程综合模拟与城乡抗震韧性重点实验室,天津300350

出　　处：《天津大学学报（自然科学与工程技术版）》2021年第8期799-806,共8页Journal of Tianjin University：Science and Technology

基　　金：国家重点研发计划资助项目(2017YFC0805407);国家自然科学基金资助项目(51578371);土木工程防灾国家重点实验室开放课题基金资助项目(SLDRCE17-01)。

摘　　要：针对运营期地铁列车荷载引起地基的长期沉降,以往三轴试验主要考虑了围压和固结比等对软土长期动力特性的影响,但在模拟地铁列车荷载时忽视了其周期性间歇的特点.基于此,本文针对天津地区饱和黏土开展了一系列间歇性循环荷载条件下的循环三轴不排水试验,分析了其对饱和黏土动应力-动应变关系、累积塑性应变及孔隙水压力发展的影响,并探讨了不同固结比和动应力比对轴向塑性累积应变的影响.研究结果表明:饱和黏土的动应力-动应变曲线的滞回形态随着振动阶段的增加逐渐向应变轴发展;黏土累积塑性应变随振动阶段发展逐渐增大且增长速率逐渐下降;由于土体滞后效应,在停振期部分累积塑性应变产生恢复,随着振次增加,各阶段残余应变值逐渐减小至一个稳定值;等压固结条件下的轴向塑性累积应变明显比偏压固结下的轴向塑性累积应变更大,同一固结条件下,轴向塑性累积应变随动应力比增大而增大;动孔压随振动阶段逐渐累积,而在前期振动循环阶段的停振阶段,累积动孔压出现略微增加;振动阶段后期部分,由于土体被压密表现为黏弹性,在停振期出现下降现象.Aiming at the long-term settlement of foundation caused by subway train load during operation period,the influence of the confining pressure and consolidation ratio on the long-term dynamic characteristics of soil has been considered in previous triaxial tests.However,the characteristics of periodicity and intermittence are ignored in the simulation of the subway train load.Based on this,a series of cyclic triaxial undrained tests under intermittent cyclic loading are conducted in this study for the saturated clay in Tianjin area.Influences of the intermittent period and frequency of vibration load on the cumulative plastic strain,dynamic stress-strain relationship,and pore pressure development of the clay are analyzed.The effect of the different consolidation ratios and dynamic stress ratios on the axial plastic cumulative strain is also discussed.Results show that with increased vibration stage,the hysteretic shape of the dynamic stress-strain curve of the saturated clay gradually develops to the strain axis,the cumulative plastic strain of clay increases,and the growth rate gradually decreases.Due to the hysteresis effect of soil mass,some accumulated plastic strain is restored in the static period.With increased vibration times,the residual strain decreases to a stable value.The axial plastic cumulative strain under constant compression consolidation is obviously larger than that under bias consolidation condition.Under the same consolidation condition,the axial plastic cumulative strain increases with the increased dynamic stress ratio.The accumulated dynamic pore pressure gradually accumulates with the vibration stage,while it increases slightly in the stopped vibration stage of the vibration cycle stage.In the latter part of the vibration stage,the phenomenon of decline occurs in the vibration stopping period due to the viscoelastic behavior of soil compaction.

关 键 词：重塑黏土 间歇性循环荷载 滞后效应 动力特性 

分 类 号：TU471[建筑科学—结构工程]