There is a ground improvement technology called the permeation grouting method, which is used as a liquefaction countermeasure for sandy ground. The ground improved by the permeation grouting method, has a large spatial variability in material property such as shear strength compared to natural soil deposits. The spatial variability in the strength property of the improved ground is anticipated to affect the deformation property under seismic loading. Therefore, a seismic deformation evaluation based on the performance specification is required considering the spatial variability of the ground. In this paper, a random field theory is used to represent the spatial variability of shear strength of the improved ground, and a seismic response analysis is conducted by Monte Carlo simulation using the dynamic finite element method. The effect of spatial variability of the improved ground on the seismic deformation of quay wall is discussed stochastically and statistically.

 If scouring occurs around the bottom of a monopile type offshore wind power facility due to waves or current, it may seriously affect the safety of the facility. The foot protection bag is a material in which rubble stones are unitized with a fiber net. It has been put to practical use as a countermeasure against erosion of breakwaters and coastal levees. In this study, we investigated the on-site applicability of scour prevention work using a foot protection bag and the optimum laying structure. The hydraulic model experiment was performed at 1/60 scale. In the unmeasured experiment, the maximum scour amount equivalent to that in the previous studies was confirmed. The scour prevention work examined the presence or absence of a filter layer and multiple laying structures. As a result, we proposed a circular arrangement with 1st layer-4row and 2nd layer-2row as the optimum structure. This arrangement can suppress the scouring near the monopile most, and the wave resistance stability of the foot protection bag itself is also improved. The maximum scouring depth in this arrangement was 0.2 m or less at the prototype.