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This study investigates the reinforcement effects of the roots of three herbaceous plants--Kentucky bluegrass, Red fescue, and Hard fescue--on the shear strength of fine-grained soil. A series of direct shear tests were conducted to evaluate how root penetration influences the shear behavior and structural stability of root-soil composites. Results indicated that root-reinforced specimens demonstrated greater ductility, with shear stress increasing in later stages of shearing, thereby contributing to soil stability. Quantitative analysis revealed that Kentucky bluegrass roots increased cohesion by 2.29 kPa and the internal friction angle by 2.6°, while Red fescue roots increased cohesion by 2.84 kPa with a slight reduction in the internal friction angle by 0.35°. For Hard fescue, cohesion increased by 3.03 kPa, with the internal friction angle decreasing by 1.54°. These findings showed that root reinforcement varied significantly under different vertical stress conditions, emphasizing the importance of environmental factors in soil behavior assessment. Comparative analysis demonstrated that each plant species exhibited unique reinforcement effects under both low and high vertical stress, providing valuable insights for designing ecological slope stabilization solutions aimed at enhancing soil stability and promoting environmental sustainability. [ABSTRACT FROM AUTHOR]

In recent years, earthquakes have caused several types of damage to residential embankments. To assess the integrity of residential embankments and ascertain necessary countermeasures following ground disasters, it is crucial to accurately define the boundary of cutting and filling. Although surface wave methods nondestructively unveil the S-wave velocity VS across a broad spectrum, there are currently no methods available to predict the boundary of cutting and filling based on VS. In this investigation, surface wave measurements were conducted in an area thought to be an embankment, according to aerial topographic interpretation. The acquired VS data were used to ascertain the soil characteristics of the unaffected residential embankment. Furthermore, the applicability of a method for predicting the boundary of cutting and fillings was examined. When the mode value of VS within the embankment was selected as the threshold for the boundary of cutting and filling, some agreement was confirmed with the outcomes calculated through aerial topographic interpretation. In addition, a straightforward technique for calculating ground subsidence based on VS was considered. It was found that it may be feasible to determine the estimated seismic settlement of residential levees swiftly and nondestructively throughout a sizable region. These results indicate that the use of the surface wave method has the potential to advance residential embankment health assessment systems. [ABSTRACT FROM AUTHOR]

In snowy cold regions such as Hokkaido, slopes can collapse owing to the frost heave phenomenon, freeze-thaw actions in winter, or snowmelt in spring. Kitami City in Hokkaido recently suffered from such slope failures when the extremely shallow layer eroded and slid after snowmelt in the early spring of 2020. The depth of this slope failure was about 0.20 to 0.25 m, which was very shallow compared with general surface failures. In this research, we conducted a site investigation of the road slope and collected undisturbed soil samples from a non-collapsed area near the slope failure to conduct a constant pressure direct shear test. For the direct shear tests, specimens with natural water content at the time of sampling and forcibly saturated specimens were used. The results of the slope stability analysis with the strength parameters obtained from the direct shear test showed that the slope failure was caused by snowmelt penetration, mainly due to a decrease in cohesion. [ABSTRACT FROM AUTHOR]

This paper aims at developing a technique for observing the frost heaving process in soil nondestructively and microscopically using an industrial micro-focus X-ray CT scanner. For this purpose, a compact frost heaving apparatus that could freeze the soil in one dimension inside the X-ray CT scanner was developed. This experimental method made it possible to observe the process of ice lens formation in the soil and the shape of the ice lens in detail. In highly frost susceptible weathered volcanic ash, ice lenses like multiple cracks were observed to develop in the early stages of the experiment. When the freezing front was stagnant and the heat was balanced, thick and well-developed ice lenses could be observed. The shape of the ice lens observed in the weathered volcanic ash without gravel was relatively flat. In the terrace deposits containing gravel, ice lenses were observed to be formed from around the larger particles. Furthermore, the formed ice lenses were more uneven in shape than weathered volcanic ash. In the case of volcanic ash sand composed of coarse grains that do not have frost susceptibility, no frost heaving occurred and no ice lenses were observed. The gray levels of the frozen areas of the weathered volcanic ash and terrace deposits with frost susceptibility were found to decrease. This is thought to be because the precipitation of ice lenses in the soil pushed the soil particles apart and reduced their density relatively. [ABSTRACT FROM AUTHOR]

In this paper, the effects of compaction method on deformation and strength properties of a sandy soil were examined by means of triaxial and unconfined compression tests and bender element test. A X-ray CT scan was also employed for providing us with image of structure of two sandy soils (n.b., sample A and B). The undrained shear strength and dilatancy characteristics were seemingly affected by the compaction method employed, and also the aspect depended on the soil type. The Ghh/Gvh -value of sample A was larger than that of sample B. The result would mean that the Ghh/Gvh -value reflecting soil anisotropy is strongly related to the shear strength and dilatancy characteristics. In addition, the variation of pd and Dc of the statically compacted specimens is more significant than that of the dynamically compacted specimens. These variations in terms of pd and Dc may also affect the deformation and strength characteristics. [ABSTRACT FROM AUTHOR]