真三轴剪切作用下粗粒料卸荷特性的研究

Experimental study on the unloading characteristics of coarse aggregate under true triaxial shear loading

在大型真三轴仪上进行一系列等向压缩与剪切作用下的加、卸载试验,阐述粗粒土的卸荷特性。重点分析不同卸载阶段回弹剪切模量的变化规律,试验结果表明:剪切过程中回弹剪切模量受应力路径影响变化较大,不能简单地用平均回弹剪切模量来代替。修正Janbu公式中,回弹剪切模量是关于小主应力和球应力2个应力变量的函数,且当其中一个变量保持不变时,回弹剪切模量随另一变量呈非线性变化,在双对数坐标上为线性形式。利用该预估模型,得到了不同剪切路径下的回弹剪切模量,模型中的参数拟合性好。模型的建立,有利于更好地理解粗粒土的卸荷特性,同时反映了应力路径及材料响应对粗粒土非线性回弹变形特性的影响。

A series of loading and unloading tests under isotropic compression and shear were carried out by using the large true triaxial apparatus,the resilience characteristics of coarse-grained soils were described,and the value of the resilience modulus in different unloading stages was analyzed. The test results show that the resilience modulus changes greatly due to the influence of stress path in the shear process and cannot be replaced by the average resilience modulus. A prediction model which involves the spherical stress and the minor principal stress was obtained from a stress-dependent analysis and the Janbu model. When one of the variables is constant,the resilient modulus changes nonlinearly with the other variable and the function relationship is linear in the double logarithmic coordinate. Using the prediction model,the resilient shear modulus under different shear paths is obtained,and the regression parameters fit well in the model. The model reflects the influence of stress path and material response on the nonlinear resilience deformation characteristics and is conducive to a better understanding of the unloading characteristics of coarse-grained soils.