主应力轴循环旋转下各向异性钙质砂的动力响应

Dynamic Shear Characteristics of Anisotropic Calcareous Sand Under Cyclic Rotation of Principal Stress Axis

为研究各向异性钙质砂在主应力轴循环旋转荷载下的动力剪切特性,利用GDS空心圆柱扭剪仪对中密钙质砂进行了各向异性固结方式下的纯主应力轴循环旋转的不排水试验,探究了中密钙质砂在动力荷载下各应变分量的发展规律和刚度变化情况。发现各向异性固结方式加剧了钙质砂试样微观结构上的各向异性,使其在主应力轴循环旋转条件下广义剪应变由“稳定型”向“破坏型”发展。对于“稳定型”试验,各应变分量基本上都随振次的对数值呈线性关系,由此得到了“稳定型”钙质砂轴向应变εz与振次N的经验公式。随着振次增加,“破坏型”钙质砂发生软化,且在10个振次以后,动剪切模量迅速单调降低,引入软化指数R N来反映动剪切模量的软化程度,得到了软化指数R N与振次N的计算经验公式。

In order to study the dynamic shear characteristics of anisotropic calcareous sand under the cyclic rotation of principal stress axis,a series of undrained tests on the cyclic rotation of principal stress axis under the anisotropic consolidation mode were carried out by GDS hollow cylinder torsional shear apparatus.It was found that the anisotropic consolidation mode aggravated the anisotropy in the microstructure of calcareous sand samples and made the generalized shear strain develop from"stable type"to"destructive type"under the cyclic rotation of principal stress axis.For the"stable type"tests,each strain component has a linear relation with the logarithm of the vibration times,thus the empirical formula of the axial strainεz and vibration times N of the"stable type"calcareous sand is obtained.With the increase of vibration times,the"destructive type"calcareous sand softens,and the dynamic shear modulus rapidly decreases after 10 vibration times.The softening index R N is introduced to reflect the softening degree,and the empirical formula for the calculation of softening index R N and vibration times N is obtained.