冻融循环作用下西宁地区黄土动力特性试验研究  

Experimental Study on Dynamic Characteristics of Loess in Xining Area under Freeze-thaw Cycles

作　　者：唐鑫 张吾渝[1,2] 童国庆 唐雄宇 刘成奎 TANG Xin;ZHANG Wuyu;TONG Guoqing;TANG Xiongyu;LIU Chengkui(School of Civil Engineering,Qinghai University,Xining 810016,China;Qinghai Province Key Laboratory of Building Energy-saving Materials and Engineering Safety,Xining 810016,China;Qinghai Provincial Key Laboratory of Plateau Green Building and Eco-community,Xining 810008,China;Qinghai Building and Materials Research Co.,Ltd,Xining 810008,China)

机构地区：[1]青海大学土木工程学院,青海西宁810016 [2]青海省建筑节能材料与工程安全重点实验室,青海西宁810016 [3]青海省高原绿色建筑与生态社区重点实验室,青海西宁810008 [4]青海省建筑建材科学研究院有限责任公司,青海西宁810008

出　　处：《防灾减灾工程学报》2023年第4期887-895,共9页Journal of Disaster Prevention and Mitigation Engineering

基　　金：国家自然基金项目(52168054);青海省高原绿色建筑与生态社区重点实验室开放基金计划(KLKF-2021-007)资助。

摘　　要：黄土作为一种广泛分布在青海省境内的特殊土,长期承受冻融循环与地震荷载的双重影响,其地震易损性和水敏性的问题一直被广泛讨论。为寻求黄土在冻融循环和动荷载耦合作用下动力特性的变化规律,以西宁地区黄土为研究对象,施加正弦波形式的循环动荷载,开展动三轴试验,分析了围压、冻融循环次数和动剪应变幅值γ_(d)对黄土的骨干曲线、动剪切模量G_(d)、动剪切模量比G_(d)/G_(d max)及阻尼比λ的演变规律。结果表明:黄土的骨干曲线在经历6次冻融循环后趋于稳定,可将骨干曲线的发展过程分为弹性阶段和弹塑性阶段;分别采用Hardin-Drnevich模型和改进的Hardin-Drnevich模型对动剪切模量曲线进行拟合,发现用改进的Hardin-Drnevich模型拟合动力参数效果较好;随着围压的降低,G_(d)/G_(d max)-γ_(d)关系曲线分布更为分散且有逐渐减小的变化趋势;随着γ_(d)的增大,λ不断增大,且土体在各围压条件下,经历不同冻融循环次数后,G_(d)/G_(d max)和λ存在最大值和最小值。该研究初步掌握了青海地区黄土在冻融循环作用下的动力学参数,研究成果可为寒区抗震设计提供设计参考。As a kind of special soil widely distributed in Qinghai Province,loess has long been impact-ed by both freeze-thaw cycle and seismic loading.The seismic susceptibility and water sensitivity of loess have been widely discussed.Taking loess in Xining area as the research object,the change rule of dynamic properties of loess under the coupling effect of freeze-thaw cycle and dynamic load was studied.The dynamic triaxial test with cyclic dynamic load in the form of sinusoidal wave was carried out,and the evolution laws of perimeter pressure,the number of freeze-thaw cycles and the amplitude of dynamic shear strain γ_(d) on the backbone curve of loess,the dynamic shear modulus G_(d),the dynamic shear modulus ratio G_(d)/G_(d max),and the damping ratioλwere analyzed.The results show that:the back-bone curve of loess tends to be stabilized after 6 freeze-thaw cycles,and the development process of the backbone curve can be divided into elastic and elastoplastic stages;the dynamic shear modulus curve is fitted by Hardin-Drnevich model and improved Hardin-Drnevich model respectively,and it is found that the dynamic parameters are fitted better with the improved Hardin-Drnevich model;with the reduction of the perimeter pressure,the distribution of G_(d)/G_(d max)-γ_(d) relationship curve is more dis-persed and has a tendency to decrease gradually;with the increase of γ_(d),λis increasing;after the loess experiences different numbers of freezing and thawing cycles,there are maximum and minimum values of G_(d)/G_(d max) andλunder various conditions of perimeter pressures.This study provided a prelim-inary understanding on the dynamic parameters of loess in the Qinghai region under the action of freeze-thaw cycle,and the research results can provide references for seismic design in cold regions.

关 键 词：黄土 冻融循环 围压 动剪应变幅值γ_(d) 动力特性参数 

分 类 号：TU43[建筑科学—岩土工程]