动荷载作用下三轴试样的体积与全表面变形测量方法

Volume and full-field deformation measurement on triaxial specimen during dynamic loading

三轴试验过程中的体积和全表面变形对研究岩土体在动、静荷载下的力学特性具有非常重要的意义。提出一个基于动态照片的多相机、多光学介质摄影测量方法来测量动荷载条件下三轴试样的体积和全表面变形。该方法通过多个相机在不同角度同时拍摄视频来获取体积和变形测量所需的同步动态照片,结合基于动态照片的相机校核结果以及多光学介质摄影测量方法可分析获得动荷载下三轴试样的体积与变形场。基于一个由6台单反相机组成的视频拍摄系统,开展一个标准钢柱和2个非饱和粉土的三轴试验来验证所提出方法的可行性以及评价其体积测量精度和全表面变形测量能力。钢柱试验结果表明该方法能够基于动态照片实现三轴试样体积的精确测量;非饱和粉土的试验结果表明该方法可以实现连续测量动荷载条件下三轴试样的体积和全表面变形。所提出的方法克服了传统动载三轴试验变形测量结果单一的局限性,将多相机、多光学介质摄影测量方法的应用从静载三轴试验推广到了动载条件;连续的体积、全表面变形测量能力为全面、深入研究土体动力特性提供了有力支持。

Volume and deformation measurement is in great significance for characterizing soil and rock mechanical behavior.In this paper,a new dynamic image-based multi-camera and multi-media photogrammetric method is proposed to measure soil deformation during triaxial testing under dynamic loading.With videos captured by multiple cameras from different view angles,dynamic images can be extracted.Together with the camera calibration results based on dynamic images and the multi-media photogrammetric method,volume and deformation of soil during triaxial testing can be measured under dynamic loading.With help of a six single lens reflex camera video capturing system,triaxial test was conducted on a steel cylinder and two silt specimens to validate the feasibility and full-field deformation measurement capability of the proposed method.Triaxial test on steel cylinder shows that the volume measurement can be made based on dynamic images at a high accuracy.The result from the triaxial test on silt specimens demonstrates that the proposed method is capable of continuous soil volume and full-field deformation measurement under dynamic loading.The proposed method overcomes the limitations associated with the conventional methods and extends the application of the multi-media photogrammetric method from static loading condition to dynamic loading condition.Continuous volume and full-field deformation measurement are beneficial for advanced characterization of soil behavior under dynamic loading.