不同幅值和频率的交通荷载下黏土变形特性研究  

Deformation Characteristics of Clay under Traffic Load with Different Amplitudes and Frequencies

作　　者：沈扬[1] 王钦城 王俊健 Shen Yang;Wang Qincheng;Wang Junjian(Key Laboratory of Geomechanics and Embankment Engineering of Ministry of Education,Hohai University,Nanjing 210098,P.R.China)

机构地区：[1]河海大学岩土力学与堤坝工程教育部重点实验室,南京210098

出　　处：《地下空间与工程学报》2022年第2期476-486,634,共12页Chinese Journal of Underground Space and Engineering

基　　金：国家自然科学基金(51979087)。

摘　　要：采用GDS空心圆柱扭剪仪对南京河西地区软黏土施加不同循环动应力比(CSR)和不同频率的模拟交通荷载,分析研究土体在交通荷载下的动力特征。试验结果表明:应变曲线随CSR的变化可分为稳定型、临界型和破坏型;在不同频率下,可用频率折减系数对广义剪应变开展进行预测;在较低的CSR(小于0.23)下土体逐渐达到准二次平衡状态,孔压趋于稳定;在较高的CSR下,土体由于结构改变无法达到准二次平衡状态,孔压逐渐上升;不同频率下的孔压变化是由塑性体积应变开展程度和单位时间内塑性体积应变累计“次数”共同作用的;土体的割线弹性(剪切)模量E_(d)(G_(d))与循环正(剪)应变幅值ε_(m)(γ_(m))的关系可以用Hardin-Drnevich模型来描述,发现1/E_(d)~ε_(m)或1/G_(d)~γ_(m)的斜率与CSR成负线性相关,而频率对土体割线模量几乎没有影响;通过计算土体的总体等效阻尼比,发现土体破坏时其值约为0.018,且该值大小随频率变化影响不大,同时相比于CSR,荷载频率对总体等效阻尼比影响较小。The GDS hollow cylinder apparatus is applied in this study to stress simulate traffic load with varied cyclic stress ratios(CSRs) and frequencies on the soft clay in Hexi area, Nanjing, hereby making analysis on dynamic characteristics of soil under traffic load. It is released that the changes of strain curve along with CSRs can be divided into three types of stable, critical, and destructive. Meanwhile, the development of generalized shear strain can be predicted by using the frequency reduction coefficient. Soil gradually reaches a quasi-secondary equilibrium state at a lower CSR(less than 0.23), and the excess pore water pressure tends to be stable. While soil cannot reach quasi-secondary equilibrium state due to structural changes at a higher CSR, the excess pore water pressure gradually rises. The change of the excess pore water pressure at different frequencies is combined by the degree of plastic volume strain development and the cumulative number of plastic volume strain per unit time. The relationship between the secant elastic(shear) modulus E_(d)(G_(d)) and the cyclic normal(shear) strain amplitude ε_(m)(γ_(m)) can be expressed by the Hardin-Drnevich model, which shows that there is a negative linear correlation between the slope of 1/E_(d)~ε_(m) or 1/G_(d)~γ_(m) and CSR. Additionally, the frequencies have little effect on the secant modulus of the soil. By calculating the total equivalent damping ratio of the soil, it is found that the value of destruction of soil is about 0.018, which has little effect on frequencies. Meanwhile, the load frequencies have less influence on the total equivalent damping ratio compared with CSRs.

关 键 词：交通荷载 饱和黏土 土体变形 Hardin-Drnevich模型 等效阻尼比 

分 类 号：TU411[建筑科学—岩土工程] TU447[建筑科学—土工工程]