考虑主应力轴偏转角影响的饱和软黏土不排水循环累积变形

UNDRAINED CYCLIC ACCUMULATIVE DEFORMATION OF SATURATED SOFT CLAY CONSIDERING INFLUENCE OF DEVIATION ANGLE OF PRINCIPAL STRESS AXIS

建立在常规循环三轴试验基础上的循环累积变形显式模型不能反映土体单元在自重应力下的初始主应力轴偏转现象,而动态空心圆柱剪切试验可为建立能反映主应力轴偏转角影响的模型提供必需试验资料。针对上海第④层饱和软黏土的物理力学特性,研制原状软黏土空心圆柱试样制样设备,同时推导恒定主应力轴偏转角时循环加载波形方程与总应力控制空心圆柱静力剪切试验加载方程。对上海地区第④层饱和软黏土进行一系列恒定主应力轴偏转角动态空心圆柱循环加载及静力剪切试验,探讨恒定主应力轴偏转角条件下饱和软黏土循环累积变形规律,在考虑主应力轴偏转角对不排水抗剪强度影响的前提下验证显式模型的合理性。考虑主应力轴偏转角循环加载的饱和软黏土显式模型可更为有效地预测路基长期沉降。

The traditional model based on triaxial cyclic loading test could not reflect the phenomenon of initial principal stress axis deviation of soil element under gravity stress. The cyclic loading test data for building the constitutive model considering the influence of deviation angle of principal stress axis can be obtained by the dynamic hollow cylinder shear test. The equipment for making the soft clay hollow cylindrical sample is manufactured according to the physico-mechanical properties of the 4th layer of saturated soft clay in Shanghai. Under the constant deviation angle of principal stress axis,the cyclic loading waveform equation and the total stress loading equation which could control the static shear test are deduced. The undrained shear tests and dynamic tests of the 4th layer of saturated soft clay in Shanghai are carried out under different constant deviation angles of principal stress axis. After discussing the rules that the deviation angle of principal stress axis affects the cyclic accumulative strain and the undrained shear strength,the explicit model is put forward which could reflect the deviation angle of principal stress axis. The model parameters are of physical significance and are easy to be obtained. The explicit model is validated based on undrained cyclic test data. It will be more effective to calculate the long-term settlement of subgrade under traffic loading with the proposed explicit model.