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利用自主开发的基于粒子群优化的数字图像相关方法,获得了单轴压缩湿砂土试样观测平面内主应变轴偏转角的时空分布规律。采用双三次样条插值方法,获取了任意位置的主应变轴偏转角,分析了土样将来出现剪切带位置、剪切带的中心及其尖端附近和剪切带外的主应变轴偏转角随纵向应变的演变规律。研究发现,随着纵向应变的增加,在土样观测平面内,主应变轴偏转角的范围由分散逐渐变得稳定,大部分区域最终分布在-10°~10°之间。当出现较清晰的剪切带以后(硬化阶段后期),剪切带内不同位置处主应变轴偏转角基本趋于恒定或稍有下降,大致稳定在-5°~5°之间,这与剪切带外的点的主应变轴偏转角均处于发展之中不同;而在剪切带尖端附近的点,主应变轴偏转角随纵向应变的演变规律比较复杂。
Using the self-developed digital image correlation method based on particle swarm optimization, the spatiotemporal distribution of the deflection angle of the main strain axis in the uniaxial compression wet sand specimen observation plane was obtained. The bilinear spline interpolation method was used to obtain the deflection angle of the principal strain axis at any position. The shear band position, the center of the shear band and the main strain axis near the tip and the shear band were analyzed. With the vertical strain evolution. The results show that with the increase of longitudinal strain, the deflection angle of the main strain axis gradually becomes stable from dispersion in the observation plane of soil sample, and the final distribution of most of the regions is between -10 ° and 10 °. When a clearer shear band appears (late stage of hardening), the deflection angle of the main strain axis tends to be constant or slightly decreases at different positions in the shear band, which is generally stable between -5 ° -5 ° The deflection angle of the main strain axis of the points outside the shear band is under development. However, at the point near the tip of the shear band, the evolution law of the deflection angle of the main strain axis with the longitudinal strain is rather complicated.