基于数字图像相关技术的砂土全场变形测量及其DEM数值模拟

FULL-FIELD DEFORMATION MEASUREMENT OF SAND USING THE DIGITAL IMAGE CORRELATION TECHNIQUE AND NUMERICAL SIMULATION USING THE DISCRETE ELEMENT METHOD

  • 摘要: 岩土材料在力学性能上表现出各向异性与非线性特征,不同土体的受力变形规律也不相同。为了更真实地反映平面应变状态下土的受力变形特性,研制了一种新型的平面应变加载设备,该设备通过对试样的侧向(围压方向上)施加柔性荷载来降低常规平面应变试验中刚性加载所造成的边界约束影响。同时,搭建了能够得到表面变形识别的数字图像采集系统。在此基础上,利用研制的平面应变设备结合二维数字图像相关技术(2D-DIC)根据获得试验过程中的全场变形来分析福建标准砂在不同围压下的变形特性。另外,通过数字图像相关法得到的平面应变试验结果来确定砂土基于抗滚动摩擦模型的细观参数,并对试验过程进行了离散元分析。结果表明:基于数字图像相关测量技术的新型平面应变试验设备可以准确获得福建标准砂的局部变形规律和变形过程的非线性行为,由此确定的砂土细观参数也能够较为真实地反映试验材料的应力-应变关系。

     

    Abstract: Geotechnical materials are characterized of anisotropy and nonlinearity. Different composition leads to different deformation in soil. In order to measure the actual deformation of soil in the plane strain condition, a new plane strain testing apparatus was used to apply flexible pressure to the lateral sides of specimens. Unlike rigid loading, this loading method reduces the influence of boundary constraints. At the same time, a digital image measuring system was combined with this apparatus to obtain the surface deformation of specimens. The 2D digital image correlation (2D-DIC) technique was used to measure the full-field deformation of Fujian (China) sand in different confining pressures. In addition, microscopic parameters of the rolling resistance linear model in the discrete element method (DEM) were calibrated by using the experimental results, and the experiments were simulated by using DEM. Results show that the new plane stain testing apparatus combined with the 2D-DIC technique can not only obtain the local deformation distribution of Fujian (China) sand but also obtain the asymmetric deformation directly. Furthermore, the calibrated microscopic parameters can truly represent the stress-strain relationship of the tested specimens.

     

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