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In tunnel construction in gravel-mixed ground, it is extremely important to predict the risk of gravel dropout and the accompanying large deformation of the substrate ground. The distribution and shape of gravel vary, and it is difficult to reproduce the situation depending on the individual site. Therefore, in this study, we created a model of the gravel-mixed ground using the Voronoi partition model. Then, by mathematical analysis, the gravel shape that appears in the actual phenomenon could be reproduced in consideration of randomness and inhomogeneity. In addition, it was clarified that the gravel extrusion phenomenon and the large deformation of the ground can be expressed.

Abstract Graphite whiskers (GWs) are obtained from coffee grounds (CGs) treated at 2500 °C for 1 h in the presence of Ar gas at 1 atm. The majority of the GWs formed inside the CGs shell are rod‐like with a conical tip with diameter and length in the range between 1 to 3 µm and 4 to 10 µm, respectively. At first, the carbon layer might be grown in a turbostratic manner, and then progressively graphitized at higher temperature. The strong G′ peak intensity might be induced by the disclination of graphitized carbon layers.