测定各向异性砂土抗剪强度特性的新型直剪装置.docVIP

 测定各向异性砂土抗剪强度特性的新型 直剪装置# 童朝霞，周少鹏，姚仰平，石光* 5 10 15 20 25 30 （北京航空航天大学交通科学与工程学院，北京 100191） 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。为研究各向异性材料任意剪切面上的抗剪强度特性，本文研制了一套可实现剪切面与沉 积面的夹角ψ在 0°~180°之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。利用该直剪装置对福建标准砂进行的ψ在 0°~180°之间、间隔为 15°的直剪 试验表明：具有最大峰值内摩擦角的面不是与沉积面垂直即ψ=90°的面，而是剪切面与沉 积面的夹角ψ≈105°的面。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。 关键词：各向异性；抗剪强度；直剪；砂土；沉积 中图分类号：TU43 An improved direct shear apparatus for shear strength of anisotropic sands Tong Zhaoxia, Zhou Shaopeng, Yao Yangping, Shi Guang (School of Transportation Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191) Abstract: 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 of any shear plane for anisotropic granular materials, an improved direct shear apparatus was designed, with which the ψ defined as the angle of shear plane with respect to the bedding plane can be changed in the range of 0°~180°. The characteristic of the improved direct shear apparatus is that its walls are independent and demountable, thus the different assemble can be made and the top or the side plane can be opened easily. By using the improved direct shear apparatus, the direct shear tests are conducted on Fujian standard sands with the ψ from 0° to 180° at intervals of 15°. The results show that the plane with the maximum peak friction angle is not the plane perpendicular to the bedding plane (ψ=90°), but that withψ≈105°. The planes corresponding to the maximum and minimum shear strength are dependent on the anisotropy degree of materials. Keywords: anisotropy; shear strength; direct shear; sand; sedimentation 35 0 引言 由于重力沉积或人工碾压等原因，砂、砾石等颗粒材料通常具有各向异性特性，即材料 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。已有研究表明：颗粒 材料的强度各向异性对评价地基承载力、边坡稳定性和土压力计算等岩土工程的经典问题具 40 有重要的影响[1-3]。譬如，Oda 和 Kois