考虑间歇效应的循环荷载下软黏土刚度软化特性  

Stiffness degradation of soft clay under cyclic loading consideringintermittency effect

作　　者：郑晴晴 夏唐代[1,2] 张孟雅[3] ZHENG Qingqing;XIA Tangdai;ZHANG Mengya(College of Civil Engineering and Architecture,Zhejiang University,Hangzhou 310058,China;Research Center of Coastal and Urban Geotechnical Engineering,Zhejiang University,Hangzhou 310058,China;Northeast Electric Power Design Institute Co.,Ltd.of China Power Engineering Consulting Group,Changchun 130000,China)

机构地区：[1]浙江大学建筑工程学院,杭州310058 [2]浙江大学城市和滨海岩土研究中心,杭州310058 [3]中国电力工程顾问集团东北电力设计院有限公司,长春130000

出　　处：《哈尔滨工业大学学报》2020年第11期88-96,共9页Journal of Harbin Institute of Technology

基　　金：国家自然科学基金(U1234204,51378463)。

摘　　要：天然软土地基在地铁运营期受到周期性振动和间歇的反复作用,间歇期内软土力学特性的变化将影响其刚度软化,但以往关于交通荷载下软土刚度软化的研究大多忽视发车间歇的影响.为此,考虑不同动应力比、单位间歇时长和振动时长,设计不排水连续和停振循环三轴试验,对试样采用真实K 0固结,研究原状淤泥质软黏土在列车非连续荷载下的长期刚度软化规律.通过对比连续振动和间歇振动试验结果,发现间歇对刚度软化有削弱作用,可减少大循环周数下残余软化指数,缩短快速软化期经历的循环周数.基于试验结果深入分析间歇的影响机制,发现加载初期软土受激振作用影响,土体结构动态调整滞后至间歇期,导致孔压持续增长,软土软化,平均软化速率提高;一定循环周数后,软土由于在前期间歇和振动阶段集中对结构进行调整,土体结构提前进入稳定状态,间歇期消散部分孔压,恢复部分刚度,导致下一次振动软化速率降低,间歇期恢复的刚度随振动次数增加而累积,致使最终残余软化指数显著提高;同等条件下,间歇时长越长,初期软化速率越大,软化速率随振动次数增加的衰减也越显著,导致进入稳定期所需的振动周数越少,整体软化程度削弱越明显.During subway operation period,the soft soil foundation is subjected to periodic vibration and intermittent loading,and changes of mechanical properties of soft soil during intermittency will affect its stiffness degradation,which has been ignored in most related previous researches.Hence,considering different dynamic stress ratios and unit intermittent and vibration durations,triaxial tests of undrained continuous and intermittent cyclic loading were designed,where samples were consolidated by real K 0,and the long-term stiffness softening rule of undisturbed soft clay under train discontinuous load was studied.Then by comparing the test results of continuous and intermittent loading,it was found that intermittent had a weakening effect on stiffness degradation,which can reduce the residual softening index under large cycle number and shorten the cycle number during rapid softening period.Finally,based on the test results,the influence mechanism of intermittent was analyzed.It was found that soft soil was affected by the excitation during initial loading,and the dynamic adjustment of the soil structure was retained to the intermittency period,which led to continuous pore water pressure generation,stiffness degradation of soft soil,and increase of the average softening rate.After a certain number of cycles,because of the structure adjustment of the soft soil under intermittent and vibration loading in the earlier stage,the soil structure entered the steady state in advance,partial pore water pressure was dissipated,and stiffness loss was restored,which led to the decrease of softening rate in the next vibration.The restored stiffness during the intermittencies was accumulated as the vibration times increased,and the final residual softening index was significantly increased.Under the same conditions,with longer intermittent duration,the initial softening rate was greater,and the attenuation of the softening rate was more significant with the increase of the vibration times,so the weakening of the overall softenin

关 键 词：间歇性循环加载 间歇效应 刚度软化 K0固结 原状软黏土 软化速率 

分 类 号：TU431[建筑科学—岩土工程]