In recent large-scale earthquake events, such as the 2011 off the Pacific coast of East Japan Earthquake, large foreshocks and aftershocks as well as the main shock had been observed at short interval. For instance, the following key factors can be considered in the soil liquefaction under multiple earthquakes: 1) intensity and interval of earthquake ground motions, 2) drainage capacity of the ground, 3) residual pore water pressure, 4) soil properties during water pressure dissipation process and after liquefaction, 5) damage status of pile foundation and embedded pipeline due to previous large motion. Soil liquefaction and associated damage from a single earthquake can be assessed by using existing assessment approach and the initial conditions, such as investigation results. However, for liquefaction caused by multiple earthquakes, it is important to estimate the ground properties including recovering due to pore water dissipation and damage status of foundation at the time of the next large earthquake motion. Because soil conditions are considerably different at each site, it is significant to collect any kind of data including experiments, numerical analysis, soil investigation, reconnaissance results under various conditions to make comprehensive estimation. To develop their dataset available for various purposes, National Research Institute for Earth Science and Disaster Resilience are planning to perform participatory research project. In this project, one of the core works is E-Defense large-scale shaking table test and the test data will be available for any participant and for any kind of researches. In this paper, contents, schedule of this project are described.

Subduction motions typically exhibit lower amplitudes, longer durations, and lower frequencies compared to crustal motions. This paper initiates the assessment of how these ground motion characteristics impact liquefaction-induced responses in sloping ground by presenting a numerical study that isolates these effects. In an initial endeavor to dissect and understand the effects of these variables, single-frequency sinusoidal ramp waves with varying amplitudes, durations, and frequencies are used in this study for fully coupled nonlinear dynamic analysis of a mildly-sloping liquefiable soil column. The analyses are carried out in OpenSees using the SANISAND-MSf v2 soil constitutive model. The simulation results indicate that increasing the maximum amplitude of the base excitation leads to a decrease in the number of cycles required to trigger liquefaction, while simultaneously increasing the end-of-motion surface lateral displacement. Increasing the number of cycles with the maximum amplitude would not affect the pre-liquefaction response if the triggering happens in the early loading cycles, but can increase the surface lateral displacements as the soil remains in the post-liquefaction stage for a longer duration. Both pre- and post-liquefaction soil responses under various motion frequencies can exhibit distinct patterns depending on the intensity of the motion and the natural frequency of the soil column.

This research conducts undrained ring shear tests with a transparent acrylic shear box, and video analysis based on videos of sand particles in the upper shear box taken from the side to evaluate sand particle behavior during liquefaction. In this test, silica sand No. 2 with large grain size (D50=1.98mm) was used to facilitate video analysis. Undrained cyclic loading tests are performed, followed by undrained monotonic loading tests at a constant shear rate by speed control while maintaining undrained conditions and constant normal stress control. After the cyclic shear test and monotonic shear test, drainage and reconsolidation under drained conditions are performed while maintaining constant normal stress. This series is one stage, and three stages of testing are performed on a single specimen. In this study, the behavior of sand particles during loading was captured by a digital video camera, and the horizontal displacement, vertical displacement, and rotation angle of the sand particles were derived. The video analysis revealed differences in the behavior of sand particles when cyclic mobility occurred and when it did not occur. During cyclic mobility, the horizontal displacement and rotation angle vibrate larger near the shear plane, indicating that the particles near the shear plane not only experienced horizontal movement but also rotational motion. On the other hand, the vertical vibrations are nearly uniform regardless of the vertical location. Therefore, uniform vertical vibrations and dilatancy could be induced by the overtaking or rotational motion of particles near the shear plane.

The increased availability of high quality data from post disaster field reconnaissance, enabled the use of deep learning algorithms in the field of geotechnical earthquake engineering. The 2010-2011 Canterbury earthquake sequence in New Zealand caused significant damage due to abundant manifestation of liquefaction induced lateral spreading. The data available from this sequence is an ideal case study for deep learning analyses due to the amount and quality of information available through the New Zealand Geotechnical Database (NZGD). A dataset of about 7500 datapoints was collected and organized by the authors to develop a new Graph Neural Network (GNN) algorithm for lateral spreading in the Canterbury area. The comparison between predicted and observed data is performed using feed forward Neural Network. Several GNN models with different hyperparameters are explored and the best model is presented in this paper, and Explainable Artificial Intelligence is applied to the model that provides the best performance. These computationally expensive analyses were carried out utilizing cloud based computing capabilities offered by the Texas Advanced Computing Center (TACC) available to the natural hazard community through the cyberinfrastructure DesignSafe.

Recently, numerous geological hazards induced by soil liquefaction have been reported in areas not traditionally considered alert zones. The multiple shocks resulting from a significant earthquake, specifically the dynamic shear history, influence the behavior of liquefaction resistance—a key factor in understanding these occurrences. Despite its significance, there is currently a lack of research aimed at determining the liquefaction behaviors subjected to dynamic shear history. This study conducted a series of cyclic triaxial tests using fine silica sand and explored the behaviors encountered during the dynamic shear history of the cyclic loading-reconsolidation progress. The results reveal that, with the maximum excess pore water pressure (EPWP) occurring during cyclic loading, liquefaction resistance undergoes two phases: an initial increase followed by a subsequent decrease compared to virgin liquefaction. The increasing phase occurs within the EPWP ratio range of 0–0.8. Notably, the maximum EPWP, rather than residual strain, governs the accumulated anisotropy and reliquefaction behaviors.

Under the actual condition of frequent earthquakes in a short time, there will be different dissipation conditions of excess pore water pressure in sand after earthquakes. Considering the different time intervals between earthquakes in a short time, this paper studies the liquefaction strength of sand under residual excess pore water pressure after earthquakes. In this paper, dynamic triaxial tests are carried out for saturated sand, and the effect of residual excess pore water pressure on liquefaction strength of sand is investigated by using the "seismic loading-interval-seismic loading" cyclic loading model. The test results show that the liquefaction strength of sand decreases, even though the sand become denser due to re-consolidation after liquefaction. Liquefaction history is the dominant factor affecting liquefaction strength of sand compared with residual excess pore water pressure induced by earthquake.

It has been reported that the liquefaction resistance of sand is largely influenced by cyclic shear history as well as the density. There are several studies proposing that dissipated energy during cyclic shear can be associated with the liquefaction resistance at next undrained cyclic shear. These previous studies only considered experimental conditions equivalent to horizontal ground where cyclic shear is symmetric. However, sloped soil or soil near structure is subjected to static shear stress and cyclic shear the soil experience during an earthquake is biased to one direction. In this study, analysis of the multiple liquefaction resistance under initial static shear was newly conducted based on dissipated energy. Experimental data by Morimoto et al. (2019a), who conducted multiple liquefaction tests on Toyoura sand using stacked-ring shear apparatus, were used. Dissipated energy is calculated by integrating the shear stress - shear strain curve during the cyclic shear. In addition to the traditional dissipated energy, the normalized dissipated energy, which uses the shear stress normalized by the mean effective stress instead of the shear stress, is also analysed as Wahyudi and Koseki (2015) and Aoyagi and Koseki (2017) did. The relationship between the liquefaction resistance of Toyoura sand and the dissipated energy (or the normalized dissipated energy) applied during previous cyclic shear is analyzed.

At 23:59 of December 18, 2023, a strong earthquake with a magnitude of M6.2 struck Jishishan county with a focal depth of 10km, in Gansu province, China. A large-scale liquefaction-triggered mud flow in loess deposit on the secondary terrace with a gentle slope of 2o-3.5o of the Yellow River, which buried 51 houses in two villages and killed 20 people. Based on a joint reconnaissance field investigation on the mud flow, the characteristics of extraordinary ground motion amplification and the large-scale mud flow were introduced. The mechanism of the liquefaction-triggered mud flow in loess deposit was analyzed. Lessons learned from the rare disasters were shared in this paper.

Pumice rich soils are found across large areas of the North Island of New Zealand. In many cases, these deposits are derived from recent volcanic eruptions in the Taupo Volcanic Zone. Pumiceous soils are characterized by their vesicular nature, which leads to the grains being lightweight, crushable, and having an extremely rough and angular surface texture. These properties give pumiceous soils particular engineering properties which are distinct from more commonly encountered hard-grained materials and make them problematic for engineers interested in assessing the risk and potential consequences of liquefactions. Natural pumice-rich soils are found with varying amounts of pumice; however, it remains unclear on how the amount of pumice present in a soil mixture alters the behavior. In this paper, three materials, obtained from the same parent material, are considered: a hard-grained sand, a pumiceous sand, and a mixture of the two. These materials were tested using a cyclic triaxial apparatus to determine the features of liquefaction resistance. It is shown that a reduction in cyclic resistance was observed due to the presence of pumice. Moreover, the majority of this effect appears to occur a relatively high portions of pumice in the soil.