基于数字图像相关技术的土体干缩开裂过程研究

Desiccation cracking bebavior of soils based on digital image correlation technique

在干燥条件下,土体极易蒸发失水收缩产生开裂,深入研究土体干缩开裂过程对准确掌握干旱气候环境中的土体工程性质响应特性具有重要意义。通过对黏性土开展室内干燥试验,采用数码相机实时记录土体表面裂隙的动态发育过程,结合数字图像相关技术,获取土体收缩开裂全过程。结果表明:①裂隙通常在土体表面张拉应力集中处产生,裂隙产生后周围应力场得到迅速释放并发生重排,且裂隙间倾向于成直角相交;②土体表面的位移场和应变场可以有效反映土体收缩开裂过程中的动态特征,能为分析和预测裂隙的演化过程提供重要参考信息;③土体被裂隙分割成不同的块区,每个块区在收缩过程中都存在收缩中心现象,且各块区的收缩中心位置会随时间而变化;④数字图像相关技术能有效识别不同图像之间的灰度特征值,能在完全不扰动土样的条件下准确获取土体表面干缩变形信息的时空演化特征,为研究土体干缩开裂动态过程及机理提供了优越的技术手段,具有较好的推广价值。

Under dry condition, the soil is prone to evaporation, leading to desiccation cracking. It is of great significance to deeply study the desiccation cracking process of soils to accurately grasp the engineering response characteristics of soils in arid climate environment. In conducting laboratory drying tests on cohesive soils, digital cameras are used to record the dynamic development of surface cracks in real time. By using the digital image correlation techniques, the plane strain field and displacement field of the whole process of desiccation cracking of soils are obtained. The experimental results show that:(1) The cracks are usually generated at the position where the tensile stress is concentrated, and the stress is then rearranged when the surrounding stress is rapidly released, and the cracks tend to intersect with other cracks at right angles.(2) The displacement field and strain field can effectively confirm some movement characteristics of the soils during the desiccation cracking process, thus providing assistance for analyzing the dynamic evolution process of cracks.(3) The soils are divided into different blocks by cracks, each block has its shrinkage center, and the shrinkage center will change with time.(4) The digital image correlation technique can effectively identify the gray scale feature values between different images, obtain the surface deformation information, and provide valid technical means for the study on desiccation cracking characteristics of soils.