中文摘要：

各向异性颗粒材料的变形和强度与相对于沉积方向的剪切方向或大主应力作用方向相关。为研究各向异性颗粒材料任意剪切面的抗剪强度特性,研制一套可实现剪切面与沉积面的夹角ψ在0°～180°全定义域区间任意变化的直剪试验装置。所研制的直剪盒的特点是各侧壁均独立可拆卸,因此在制样过程中可根据不同的需要进行组装,使该直剪试验盒的某些侧面和顶面打开。在验证该直剪试验装置有效性的基础上,对福建标准砂进行ψ在0°～180°范围内、间隔为15°的系列直剪试验。试验结果表明：ψ在0°～90°区间的某个面相对应有最小峰值内摩擦角,此后峰值内摩擦角随的增加而增加;但具有最大峰值内摩擦角的面不是与沉积面垂直即=90°的面,而是ψ〉90°（ψ≈105°）的某个面。材料各向异性程度不同,相对应最大和最小峰值内摩擦角的ψ亦不同。

英文摘要：

The deformation and shear strength of anisotropic granular materials are dependent on the shearing direction or the orientation of principal stress relative to the bedding plane.In order to investigate the shear strength properties of any shear plane for anisotropic granular materials,an improved direct shear apparatus was designed,with which the ψ of Fujian standard sand defined as the angle of shear plane with respect to the bedding plane can be changed in the whole range of 0°–180°.The characteristics of the improved direct shear apparatus is that its walls are independent and demountable,thus the apparatus can be assembled according to different needs;and some top and side surfaces can be opened.By using the improved direct shear apparatus,direct shear tests are conducted on Fujian standard sands with the variation of ψ from 0°to 180° at intervals of 15°.The experimental results show that the plane with the minimum peak internal friction angle is achieved at the angle of ψ from 0° to 90°.After that,the peak internal friction angle increases with the increasing ψ.However,the plane with maximum peak internal friction angle is not the plane perpendicular to the depositional plane（ψ = 90°）,but that with ψ ≈105°.The planes related to the maximum and minimum peak internal friction angles are dependent on the anisotropy degree of materials.