After serving for a long time, the surface of CRTS Ⅱ slab track generates crack with the positions and directions varied. It was found from the on-the-spot investigation that, in the vicinity of rail support platform, the transverse crack in slab track was salient. By using the image processing techniques and fractal theory, the paper analyzed the character of transverse crack growth for slab track. The computation shows that support rail bed has a concentrated load effect, which makes the slab track nearby easy to appear crack; the edge of slab track prestressed rebar is easy to appear earlier cracking phenomena. In addition, the crack will grow along the prestressed rebar direction; the cracks in slab track has fractal feature, and the fractal dimension will enlarge with the increase of crack length. The results can be used as characteristic attribute index for crack growth of slab track.%CRTSⅡ型无砟轨道板在长期服役状态下,表面产生裂纹,其位置和方向多种多样.从现场调查情况可以看出,轨道板在承轨台邻近处横向裂纹尤为突出.运用图像处理技术和分形理论对轨道板横向裂纹扩展特性进行分析.计算分析表明:承轨台受荷载作用集中,邻近处轨道板易产生裂纹;轨道板内预应力钢筋边缘易产生先开裂现象,并且裂纹沿着预应力钢筋方向扩展;轨道板裂纹具有分形特征,分形维数随裂纹长度增长而增大,可以作为轨道板裂纹扩展的特征属性指标.
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