裂隙是影响膨胀土力学特性的重要因素之一。以河南南阳地区高速公路路用膨胀土为研究对象,通过制备不同初始含水率和压实度的大尺寸压实膨胀土土样,观察压实膨胀土在脱湿过程中的表面裂隙发育,并拍摄数码图像,然后利用基于MatLab自编程序的改进裂隙图像特征参数提取方法对图像进行定量化分析,获得裂隙的各种特征参数,进而探讨膨胀土表面裂隙发育的相关规律。研究结果表明:压实膨胀土脱湿开裂过程可分为细小裂隙发育、主裂隙发育及裂隙回稳3个阶段;初始含水率越高,膨胀土表面裂隙发育速率越快,发育程度越高,持续时间越长;初始压实度越大,膨胀土表面裂隙率和裂隙总长越小,但宽度较大。上述裂隙发育规律可用表面蒸发和土体内部水分传输机理进行解释。
Abstract
Crack is a crucial factor that affects the mechanical properties of expansive soil. Expansive soils taken from Nanyang Expressway (Henan Province, China) were compacted to big-size samples with various original water content and compactness, and then the samples were desiccated gradually in a closed greenhouse where a camera was used to record the propagation of cracks on the surfaces of samples. The captured images were analyzed quantitatively using self-compiled program of MatLab to obtain the characteristics of surface cracks which were further used to explore the laws of crack propagation. The results suggest that the course of crack propagation in compacted expansive soil samples can be divided into three stages: in the first stage minor cracks aroused and developed quickly; then main cracks emerged and cracks reached peak in the second stage; at last the cracks withdrew and remained stable in the third stage. The higher the original water content was, the faster the cracks on the surfaces of expansive soil samples developed, the higher the extent of crack development was, and the longer the crack development lasted; the higher the original compactness, the smaller the surface crack ratio and total length of expansive soil samples were, but the larger the crack width was. The above results can be explained by the mechanism of superficial evaporation and water transformation in the soil.
关键词
膨胀土 /
裂隙发育 /
数码图像 /
二值化图像 /
裂隙率 /
压实度 /
初始含水率
Key words
expansive soil /
crack propagation /
digital image /
binary image /
crack ratio /
compactness /
initial water content
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