The types of embankment damage during earthquakes are crest or slope tension cracking and circular sliding. However, it remains unclear which damage occurs during which earthquake. We conducted a crack propagation analysis using peridynamics (PD) to study type of damage of embankments. The results showed that the type of damage varies with maximum acceleration and frequency. However, the analysis was limited to 2D. Therefore, a 3D seismic response PD is developed and compared with the 2D PD to demonstrate the validity of the code. We also investigate the influence of maximum acceleration and frequency on the damage.

The sheet pile with drainage ability installed at embankment toes is a liquefaction countermeasure technique that had been extensively employed for river levees. Combined effects of providing lateral confinement to liquefied sand below the levee and drainage ability that accelerates the excess pore pressure dissipation are expected to reduce levee settlement. Since the L2 earthquake was stipulated in the design standards, the technique has not been used because of the difficulties to restrain excess pore pressures below the liquefaction level. However, case histories were reported where deformation was smaller for ground with drains implemented even though the ground liquefied. In this study, a series of centrifuge tests was conducted to investigate the effects of the drainage ability attached to sheet pipes to reduce levee subsidence due to foundation liquefaction. It is confirmed that the effectiveness of the drainage ability in reducing settlement depends largely on the hydraulic conductivity of sand, and that there is a range of hydraulic conductivity within which the effectiveness of the countermeasure increases rapidly. The drainage members on the sheet piles significantly reduce shear deformation around sheet pipe and levee toes even though the soil liquefied.

This study focuses on the influence of stiffness and softness of supporting ground on the seismic displacement of embankments, and the verification of its evaluation method. Conventionally, the seismic displacement of embankments has been calculated using the Newmark's sliding block analysis method, comparing it with the displacement limit in a design code to evaluate the seismic performance of the embankments. On the other hand, previous studies have pointed out that the observed seismic displacement of the embankments can be different from that calculated by the Newmark's sliding block method for embankments on soft supporting ground. Therefore, a series of shaking table experiments was conducted using a 1/10 scale model of an embankment on supporting ground with different total densities to confirm the influence of stiffness and softness of the supporting ground on the seismic displacement of embankments. Furthermore, verification analyses were performed using both the Newmark's sliding block analysis method and the mesh free method. As a result, it was found that the softer the supporting ground, the larger the deformation of the embankment becomes during an earthquake, leading to an increased displacement. This caused that the Newmark's sliding block analysis method can particularly underestimate the seismic displacement of embankments on the soft supporting ground. In addition, based on the experimental results and analytical results using the mesh free method, the mechanism behind the occurrence of the seismic displacements was discussed.

In the 2018 Hokkaido Eastern Iburi Earthquake, 28 residential lots facing the Omagari River collapsed in the Omagari Namiki 3-chome district of Kitahiroshima City. The main damaged residential area was located in a corner of a long and narrow town block facing the right bank (east side) of the Omagari River. In this paper, we analyzed the collapsed embankment damage in the Omagari Namiki 3-chome district of Kitahiroshima City, and verified the effectiveness of the countermeasure against sliding collapse using the groundwater level lowering method.

The "Guide to Measures against Liquefaction of River Embankments" lists "compaction method" as one of the liquefaction countermeasures. Among compaction methods, the sand compaction pile (SCP) method is the most typical method and can be classified into three types: the "SCP method for vibratory type (vibratory SCP)”, the "Static compaction sand pile method for non-vibratory type (non-vibratory SCP)”, and the "Static compaction method for sand injection type with small machine (sand- injection type SCP). In this paper, we report on examples of river embankments where the SCP method was used for restoration work and seismic countermeasures improved just below and at the bottom of slope, and on the improvement effects of the method. In recent years, it has become possible to apply the slanting improvement method using a small machine, and the influence and factors of the improvement location (just below, at the bottom of the slope, or at an angle) on the amount of settlement of the embankment top are discussed based on the results of static deformation analysis (ALID) when the compaction improvement is applied to liquefaction countermeasures for embankments.

In recent years, reinforcements of railway embankments have been conducted for increasing the seismic resistance. Reinforcements of embankment body using soil nails are often adopted. For the prevention of seepage and erosion to rainfall, slope protection works are also constructed. The works can also contribute to the increase of seismic performance by connection with soil nails. However, these effects have not been studied clearly. In this paper, series of shaking table tests of model embankments with slope protection works and soil nails were conducted. From the series of shaking table tests, it was revealed that the seismic resistance of the embankment was increased by the slope protection works due to increasing the extension force of soil nails by connecting with the works. Furthermore, the design method of reinforcement of embankment was developed and validated.

Deformation analysis of embankments is often performed under small deformation conditions because the displacement is assumed to be controlled against a specific external force. However, considering the increasing severity of external seismic forces, large deformations/geometrical nonlinearities must be considered in deformation analysis. In this paper, we report the applicability of the particle method that can be applied to the analysis of the earthquake response of embankments considering slope failures, and the differences in response characteristics depending on whether geometric nonlinearities are considered. The experimental and analytical results were consistent in terms of soil mass formation and slope failure modes, indicating that the proposed method that considers geometric nonlinearity and material softening is applicable to the seismic response analysis of embankments considering slope failures.

We conducted a seismic response analysis focusing on seismic duration and its periodic characteristics. It is shown that when the long period component of the input earthquake motion is dominant, not only liquefaction in sandy layers but also disturbance in clayey layers, which are conventionally considered to be less susceptible to seismic damage, is caused by strong shaking due to resonance. In addition, the earthquake motion for designing river levees is often specified by the seismic response spectrum and the effect of seismic motion duration is not explicitly taken into account, but in soft ground with strong elasto-plastic non-linearity, the effect of the duration becomes significant.

The procedures of the assessment of the seismic safety of agricultural reservoir embankments and implementation of countermeasures are described. The slip analysis by Newmark-D method and the residual deformation analysis by non-linear FEM, both accounting for significant effects of compaction on undrained shear strength of saturated soil and its reduction during seismic loading, are reported. By these methods, the collapse of a reservoir embankment by strong seismic loads was successfully simulated, while a high stability against level 2 seismic load of the restored embankment was confirmed. The new dam was constructed by effective compaction controlling the degree of saturation in addition to the dry density and water content.

The Fukushima-oki earthquake of March 16, 2022 (M7.4) caused damage to port facilities of Soma Port. Soma Port has a large number of sheet pile quaywalls, and the residual displacement of the sheet piles was measured by a diving survey after the earthquake. It is important to evaluate the deformation patterns of sheet piles in order to assess the stress state of the structural members and to determine whether the facility can be used after the earthquake. This report summarizes the identified deformation patterns of sheet pile quaywalls and discusses factors that led to each deformation pattern.

A reproductive case study was conducted using a simple stability computation by the seismic coefficient method based on the time history of the excess pore water pressure ratio and the response acceleration obtained from reproductive FEM analysis of residential land embankments where residual deformation occurred. Based on the results, parameters used in the stability computation such as strength parameters, horizontal seismic coefficient, and pore water pressure that can adequately reproduce the occurrence of residual deformation were examined.

Three tailings dams failed during the 2011 Tohoku Earthquake. The failed tailings dams had been investigated before the earthquake and judged to be stable. Then, it was considered necessary to inspect the tailings dams deemed susceptible to damage by very strong level 2 earthquake motion. And, it was considered necessary to introduce a new design concept based on the likely degree of damage from sliding. Then, it was decided to analyze the amount of deformation using a dynamic analysis method by considering liquefaction, and seismic inspections began to be carried out based on the amount of slip displacement.

On August 11, 2009, an earthquake centered in Suruga Bay caused the collapse of the embankment of the Tomei Expressway. The reason for the embankment collapse was that the mudstone used for the lower part of the embankment had lost its strength and permeability due to the action of water over many years, causing the groundwater level in the embankment to rise. The collapse was estimated to have been caused by seismic shaking. Following this disaster, inspections of embankments under similar conditions were carried out, and it was confirmed that the strength of embankments where spring water was confirmed was low. This paper describes the transition of seismic countermeasures for expressway embankments and design criteria for mudstone embankments and introduces a series of efforts from inspection to evaluation and implementation of countermeasures. It also discusses issues regarding ensuring the seismic resistance of existing embankments using mudstone.