交通荷载作用下考虑累积塑性应变的饱和软黏土应变软化特性研究  

Research on Strain Softening Characteristics of Saturated Soft ClayConsidering Accumulative Plastic Strain under Traffic Load

作　　者：孙苗苗 虞健刚 何绍衡 叶科 刘旻 SUN Miaomiao;YU Jiangang;HE Shaoheng;YE Ke;LIU Min(Department of Civil Engineering,Zhejiang University City College,Hangzhou 310015,China;Department of Civil Engineering,Zhejiang University,Hangzhou 310058,China;Key Laboratory of Safe Construction and Intelligent Maintenance for Urban Shield Tunnels of Zhejiang Province,Hangzhou 310015,China)

机构地区：[1]浙大城市学院土木工程系,浙江杭州310015 [2]浙江大学土木工程系,浙江杭州310058 [3]浙江省城市盾构隧道安全建造与智能养护重点实验室,浙江杭州310015

出　　处：《铁道学报》2023年第4期148-156,共9页Journal of the China Railway Society

基　　金：浙江省自然科学基金(LY18E080024);浙江省科技计划(2020C01102)。

摘　　要：长期往复交通荷载将引起显著的路基沉降,而现有路基长期运营沉降分析多数建立在循环三轴试验基础上,忽视了交通荷载下土体单元主应力轴的偏转效应。通过对杭州原状软黏土进行应力控制的空心扭剪试验,研究循环应力比CSR、偏应力固结比K 0、振动频率f的变化与软化指数、累积塑性应变的关系。研究表明:对于各向同性固结软黏土,初始累积塑性应变为负应变,并随着振动次数的增加而逐渐增大(负应变),而K 0固结的初始累积应变为正应变;K 0和振动频率的减小增大了土样的初始累积塑性应变,加快土样破坏速度。在试验结果的基础上,确定软化指数与振次的对数关系表达式,引入累积塑性应变影响因子ζ,建立原状软黏土累积塑性应变模型,为预测和计算地基土层的长期沉降变形提供理论依据。Long-term cyclic traffic loads will cause significant roadbed settlement,while the existing long-term operation settlement analysis of roadbeds is mostly based on cyclic triaxial tests,ignoring the deflection effect of the principal stress axis of the soil element under traffic load.Through the stress-controlled hollow cylinder torsional shear test of Hangzhou undisturbed soft clay,the relationship between cyclic stress ratio(CSR),deviatoric consolidation ratios(K 0),loading frequency change(f),degradation index and accumulative plastic strain was studied.The results show that for the consolidated isotropic soft clay,the initial cumulative plastic strain is negative strain,which gradually increases with the increase of the number of vibrations(negative strain),while the initial cumulative plastic strain of K 0 consolidation is positive strain.The decrease of K 0 and the vibration frequency increases the initial cumulative plastic strain of the soil sample and accelerates the failure rate of the soil sample.Based on the test results,the logarithmic relationship expression between the softening index and the vibration frequency is determined.The cumulative plastic strain influence factorζis introduced to establish the cumulative plastic strain model of the undisturbed soft clay,which provides a theoretical basis for predicting and calculating the long-term settlement and deformation of the foundation soil.

关 键 词：空心扭剪 K 0固结 原状软黏土 累积塑性应变 主应力轴偏转 应力应变 

分 类 号：TU443[建筑科学—岩土工程]