It can often be seen that trees and roots intrude fractures at rock slopes. Under these situations, it is expected that the rock slope can gradually become unstable with the growth of the trees and roots, and eventually, rockfall may occur. In this study, fracture displacements were measured in-situ for three and a half years at a rock slope in Hakodate, Japan, facing the Pacific Ocean. As a result, an apparent long-term fracture opening was observed during the tree growth period from spring to summer. There are also small disturbances in the displacement with shorter periods. Comparison with weather data suggests that the fractures tended to open slightly due to rainfall and when the wind blew from the ocean. A slight opening caused by an M5.3 earthquake was also observed.

 This paper proposes a method for calculating the earthquake damage probability of railway embankments based on seismic hazard information and a newly developed fragility curve estimation equation. Assuming that the fragility curve of the railway embankment is a cumulative lognormal distribution, a quasi-Monte Carlo simulation of permanent seismic displacements using the Newmark method was conducted to develop an estimating equation for the fragility curve. Using the proposed method, a nationwide earthquake damage probability map of railway embankments was created, and the seismic performance of railway embankments was probabilistically evaluated.

 Sediment runoff at steep slopes is one of the serious problems about sediment disasters caused by heavy rains. Establishing proper methods for its risk assessment has today become an urgent issue to combat the problem. This study, by conducting a field survey and topographic reading in three locations affected by Heavy Rain in July 2018 and with different foundation geology, investigates how different topographic characters and different foundation geology of zero-order basins are related to sediment runoff from them. As a result, we find that sediment runoff from zero-order basins is closely related to the development of basins. It tends to occur at zero-order basins which have a loose sediment layer with less than 20 N_d and more than 1.1m depth. We observe no correlation between sediment runoff and foundation geology or ground material. Zero-order basins with a high risk of sediment runoff can be extracted by topographically monitoring the total valley length and the maximum b/a which increases with the development of valleys.

 Slope protection frames are indispensable to prevent local disasters in Japan where torrential rains and earthquakes occur frequently. Conventional slope protection frames, which are typically constructed by shotcreting using low-slump mortar delivered by air, often face a problem of inadequate strength due to separation of aggregates. We developed a material delivery system in which a typical concrete pump for civil works is used to deliver the material and air is injected at the end of the delivery pipe. With this system, a high-slump material can be delivered over a long distance to a high-altitude site without causing material separation and can be placed in formwork at a steep slope using compressed air. Blowing air into the material reduces the slump and enables the material to be placed without causing separation or flow-out. When air is added to the material, water droplets are scattered at the nozzle. We focused on this phenomenon and developed measures to control the slump after placement. Moreover, addition of sepiolite improved separation resistance and flow-out resistance of the mortar after placement, which led to an improvement in the product quality of the slope protection frames.

 A series of numerical analyses of singular ground deformation is carried out, focusing on the relation between the rate dependent property of the ground and the velocity of forced sharing displacement. We modeled the ground by the generalized Maxwell model, and we set a potential discontinuity in the ground and modeled it by the X-FEM. Then, for various speeds of the uplift of the base rock we examined whether a shearing failure would occur along the potential discontinuity or, instead, a viscoelastic deformation would dominate. The results show that if the ground is subjected to a forced displacement of a half of its thickness, a sharing failure probably occurs when the displacement is applied with a speed that takes time equal to or shorter than the relaxation time, and that a continuous viscoelastic deformation would dominate only when the forced displacement is applied with more sufficiently slow speed.

 The purpose of this study is to clarify the relationship between the light intensity measured by a plastic optical fiber moisture detection sensor (RR sensor) and the volumetric moisture content measured by a soil moisture meter. The results of watering experiments using an optical information processing application for portable devices and soil columns indicate that the progression of the ground from a quasi-saturated state to a saturated state can be determined by measuring the light intensity. The rate of decrease in light intensity was found to increase near the point where the quasi-saturated volumetric water content was exceeded. These results suggest that the results of light intensity measurements in the ground by the RR sensor can be used to evaluate the risk of slopes.

 Twin large shield tunnels for highway services were excavated above and below an existed shield tunnel. The deformations of the existing tunnel were measured during nearby shield tunneling. The vertical and horizontal inner deformations of the existing tunnel were measured by specific fiber optics being called BOTDR. The deformations of the cross-section of the existing tunnel were detected with an accuracy of 0.05 mm. This paper is described remarkable knowledge of the vertical and horizontal deformations of the cross-section of the existing tunnel being influenced by upper and lower parallel shield tunneling. The authors also proposed the simple 2D FEM with the inclusion of the self-weight of the shield machine in the simultaneous excavation of vertical parallel shield tunnels. The construction data being corresponded to the shield tunneling are applied to analyze the changes of the deformations of the existing tunnel and nearby ground stresses. The results of the calculation showed good agreement with the deformations of the cross-section of the existing tunnel. As the result, we could propose a predictive calculation method for vertically parallel shield tunneling.