冻融循环对青藏粉质黏土动力非线性参数影响的试验研究  

Experimental study of influence of freeze-thaw cycles on dynamic nonlinear parameters of Qinghai-Tibet silty clay

作　　者：苏永奇 马巍 钟秀梅[4] 王谦[4] 穆彦虎 高中南 SU Yongqi;MA Wei;ZHONG Xiumei;WANG Qian;MU Yanhu;GAO Zhongnan(State Key Laboratory of Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou,Gansu 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;Gansu Bureau of Coal Geology,Lanzhou,Gansu 730000,China;Lanzhou Institute of Seismology,China Earthquake Administration,Lanzhou,Gansu 730000,China)

机构地区：[1]中国科学院西北生态环境资源研究院冻土工程国家重点实验室,甘肃兰州730000 [2]中国科学院大学,北京100049 [3]甘肃煤田地质局,甘肃兰州730000 [4]中国地震局兰州地震研究所,甘肃兰州730000

出　　处：《岩石力学与工程学报》2020年第S01期2973-2985,共13页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(41630636,41772325);兰州市科技计划项目(2018–1–123)。

摘　　要：为研究冻融循环次数、动荷载频率和含水率等因素对青藏粉质黏土动力非线性参数的影响,在室内冻融循环试验的基础上开展动三轴试验,得出动剪应力与动剪应变(τ_d-γ_d)骨干曲线、动剪切模量比与动剪应变(G_d/G_(dmax)-γ_d)关系曲线。结果表明:不同冻融循环条件下重塑青藏粉质黏土的动力特性曲线符合Hardin-Drnevich双曲线模型,冻融循环次数、频率及含水率对青藏粉质黏土的动力非线性参数均有显著影响,6次冻融循环后青藏粉质黏土的动力非线性参数趋于稳定,冻融循环过程中孔隙水冻结相变引起的土体结构劣化是青藏粉质黏土动力性能剧烈变化的内在原因。当γ_d不变时(如γ_d=0.001),随冻融循环次数的增加,τd先快速减小后略有增大,Gd/Gdmax变化不大,含水率18%的试样在经历1,3,6,10次冻融循环后,τd分别减小了35.4%,48.6%,41.6%,43.0%,Gd/Gdmax分别减小了6.1%,0.5%,-1.2%,0.4%;随频率的增加,τd不断增大,G_d/G_(dmax)不断减小,当频率从0.5 Hz增加到5 Hz,对于含水率为18%,经历0,1,3,6次冻融循环的试样,τd分别增大了14.4%,22.1%,68.8%,52.6%,G_d/G_(dmax)分别减小了4.9%,17.2%,32.8%,22.6%;随含水率的增加,τ_d和G_d/G_(dmax)均不断减小,当含水率从13%增加到19.5%,对于经历0,1,3,6,10次冻融循环的试样,τd分别减小了53.7%,70.6%,77.8%,78.6%,78.5%,G_d/G_(dmax)分别减小了18.5%,27.7%,28.8%,24.6%,30.0%。研究成果可为寒区场地地震反应分析提供融土动力学参数。Based on the freeze-thaw cycles tests,the dynamic triaxial tests are carried out to study the dynamic nonlinear parameters of Qinghai-Tibet silty clay.In the test,the effects of freeze-thaw cycles,dynamic loading frequency and moisture content are considered.Then,the backbone curve of dynamic shear stress vs.dynamic shear strain(τd-γd)and the relationship curve of dynamic shear modulus ratio vs.dynamic shear strain(Gd/Gdmax-γd)are obtained.The results indicate that the dynamic behavior of the remolded Qinghai-Tibet silty clay can be described by Hardin-Drnevich hyperbolic model.Freeze-thaw cycles,frequency and moisture content all have significant influence on the dynamic nonlinear parameters of Qinghai-Tibet silty clay,which tend to be stable after 6 freeze-thaw cycles.With the phase transition of pore water during freeze-thaw cycles,the soil structure was deteriorated.It is the inherent mechanism for the drastic changes of dynamic behaviors of Qinghai-Tibet silty clay.Whenγd is constant(e.g.,γd=0.001),τd decreases rapidly first,then increases slightly,and Gd/Gdmax does not change much as the number of freeze-thaw cycles increases,for the sample with moisture content of 18%that has subjected of 1,3,6 and 10 freeze-thaw cycles,τd decreases by 35.4%,48.6%,41.6%and 43.0%,Gd/Gdmax decreases by 6.1%,0.5%,–1.2%and 0.4%respectively.With increasing frequency,τd increases and Gd/Gdmax decreases continuously,as frequency increases from 0.5 Hz to 5 Hz,for the sample with moisture content of 18%that has subjected of 0,1,3 and 6 freeze-thaw cycles,τd increases by 14.4%,22.1%,68.8%and 52.6%,Gd/Gdmax decreases by 4.9%,17.2%,32.8%and 22.6%respectively.Both ofτd and Gd/Gdmax decrease continuously as the moisture content increases,as moisture content increases from 13%to 19.5%,for the sample that has subjected of 0,1,3,6 and 10 freeze-thaw cycles,τd decreases by 53.7%,70.6%,77.8%,78.6%and 78.5%,Gd/Gdmax decreases by 18.5%,27.7%,28.8%,24.6%and 30.0%respectively.The research results can provide the dynamic parameters o

关 键 词：土力学 粉质黏土 冻融循环 动三轴试验 动剪切模量比 含水率 频率 

分 类 号：TU43[建筑科学—岩土工程]