基于摄影重构技术的三轴试样变形测量研究

Research on deformation measurement of triaxial specimen based on photographic reconstruction technology

为克服传统三轴仪对土样变形的限制,获取三轴试样真实的轴向、径向应变,将摄影测量技术与数字图像技术相结合,对常规三轴仪进行微小改动,利用单镜头相机对三轴试验全过程进行图像采集,重构土样在不同加载阶段的三维模型,从而获取试样的真实变形数据。结果表明:1)经折射修正后的摄影测量法在三轴试验中有较高的精度,其中轴向测量值整体误差在0.104 mm;径向截面最大测量误差为0.211 mm,最小误差在0.138 mm,基本满足实验所需。2)获取土样局部与整体的轴向、径向变形数据。与常规三轴试验所测结果相比,摄影重构法所得试样整体轴向应变偏小,整体径向应变偏大,整体强度偏小,运用摄影重构法能对土样具体区域变形进行直接测量,结果更符合实际。

In order to overcome the limitation of the traditional triaxial apparatus on the deformation of soil samples and obtain the true axial and radial strains of triaxial specimens,the photogrammetry technology and digital image technology are combined to make minor changes to the conventional triaxial apparatus.The single lens camera is used to collect the images of the whole process of triaxial test,and reconstruct the three-dimensional model of soil samples in different loading stages,so as to obtain the true deformation data of the specimens.The results show that:1)the photogrammetric method after refraction correction has high accuracy in triaxial test,in which the overall error of axial measurement value is 0.104 mm.The maximum radial section measurement error is 0.211 mm,and the minimum error is 0.138 mm,which basically meets the needs of the experiment.2)The axial and radial deformation data of local and overall soil samples were obtained.Compared with the results of conventional triaxial tests,the overall axial strain of the sample obtained by the photographic reconstruction method is smaller,the overall radial strain is larger,and the overall strength is smaller.The photographic reconstruction method can be used to directly measure the deformation of the specific area of the soil sample,and the results are more in line with the reality.