Abstract
Expansive soil is prone to cracks under a dryingāwetting cycle environment, which brings many disasters to road engineering. The main purpose of this study is use coal gangue powder to improve expansive soil, in order to reduce its cracks and further explore its micro-pore mechanism. The dryingāwetting cycles test is carried out on the soil sample, and the crack parameters of the soil sample are obtained by Matlab and Image J software. The roughness and micro-pore characteristics of the soil samples are revealed by means of the Laser confocal 3D microscope and Mercury intrusion meter. The results show that coal gangue powder reduces the crack area ratio of expansive soil by 48.9%, and the crack initiation time is delayed by at least 60 min. Coal gangue powder can increase the internal roughness of expansive soil. The greater the roughness of the soil, the less cracks in the soil. After six dryingāwetting cycles, the porosity and average pore diameter of the improved and expanded soil are reduced by 37% and 30%, respectively, as compared to the plain expansive soil. By analyzing the cumulative pore volume and cumulative pore density parameters of soil samples, it is found that the macro-cracks are caused by the continuous connection and fusion of micro-voids in soil. Coal gangue powder can significantly reduce the proportion of micro-voids, cumulative pore volume, and cumulative pore density in expansive soil, so as to reduce the macro-cracks.
Highlights
Expansive soil is a type of high plastic clay rich in high hydrophilic montmorillonite, illite, and other clay minerals
Many scholars have begun to study the development of cracks in expansive soil, by using relevant computer technologies and image recognition technologies to extract cracks, and quantitatively analyzing the parameters of the extracted cracks, in order to obtain the related characteristics of soil crack development [6,7,8]
These results demonstrate that the crack area ratio increases rapidly between 120 and 960 min, and the increasing speed of the crack area ratio increases with the increase in the dryingāwetting cycles
Summary
Expansive soil is a type of high plastic clay rich in high hydrophilic montmorillonite, illite, and other clay minerals. Many scholars have begun to study the development of cracks in expansive soil, by using relevant computer technologies and image recognition technologies to extract cracks, and quantitatively analyzing the parameters of the extracted cracks, in order to obtain the related characteristics of soil crack development [6,7,8]. Li et al [22] improved the expansive soil with sand, and studied the effects of sand content and particle size on the development of expansive cracks. The results show that the crack rate of soil sample decreases gradually with the increase in sediment content and particle size. Most scholars have only studied the development of soil cracks, but there is still a lack of research on the micro-pore evolution mechanism of macro-crack development and the influence of crack surface roughness on crack development
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