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This study presents a gradient damage model for ductile fracture, in which the damage hardening modulus is degraded by the accumulation of plastic deformation and the volume expansion caused by negative hydrostatic pressure. The proposed model fulfills the thermodynamic requirements, and the governing equations are derived from energy minimization principles. Two parameter studies are carried out to confirm the basic performance of the proposed model, in which some typical ductile fracture responses are demonstrated by changing parameters for degrading the damage hardening modulus. Also, a series of numerical experiments are presented to reveal the ability of the proposed model to successfully simulate the fracture tests of advanced high strength steel sheets with different tensile strengths. It is indeed confirmed by the close agreement with experimental results that the proposed model is capable of realizing the breaking elongation, the transitional behavior from unstable to stable crack propagations, and the corresponding load–displacement curves. Also, the model successfully reproduces and predicts the crack initiation positions in notched specimens with different notch radii. [ABSTRACT FROM AUTHOR]

This study presents a novel phase-field model for ductile fracture by the introduction of both the plastic driving force and the degrading fracture toughness into crack phase-field computations based on the phenomenological justification for ductile fracture in elastoplastic materials. Assuming that the constitutive work density consists of elastic, pseudo-plastic and crack components, we derive the governing equations from local and global optimization problems within the continuum thermodynamics framework. In addition to the elastic strain energy, the plastic strain energy also works as a driving force to sustain damage evolution. Additionally, we introduce a degrading fracture toughness to reflect the evolution of micro-defects and their coalescences into each other that are caused by accumulated plastic deformation. Equipped with these ingredients, the proposed model realizes the reduction of both stiffness and fracture toughness to simulate the failure phenomena of elastoplastic materials. Several numerical examples are presented to demonstrate the capability of the proposed model in reproducing some typical ductile fracture behaviors. The findings and perspectives are subsequently summarized. [ABSTRACT FROM AUTHOR]

The present study proposes an MPM (material point method)–FEM (finite element method) hybrid analysis method for simulating granular mass–water interaction problems, in which the granular mass causes dynamic motion of the surrounding water. While the MPM is applied to the solid (soil) phase whose motion is suitably represented by Lagrangian description, the FEM is applied to the fluid (water) phase that is adapted for Eulerian description. Also, the phase-field approach is employed to capture the free surface. After the accuracy of the proposed method is tested by comparing the results to some analytical solutions of the consolidation theory, several numerical examples are presented to demonstrate its capability in simulating fluid motions induced by granular mass movements. [ABSTRACT FROM AUTHOR]

By utilizing the Green-Ampt infiltration equation and the infinite slope stability model, a method for analyzing shallow slope failures caused by rainfall is developed. With rainfall intensity, soil characteristics, and topography, the modified Green-Ampt infiltration equation is used to estimate the rainfall infiltration capacity and depth of infiltration in a given slope. Assigning the calculated depth of infiltration as the depth of slip surface, the factor of safety of the slope is obtained through the infinite slope stability model. A time-series visualization map of the space-time varying factor of safety is generated when the method is implemented with the aid of Geographic Information System (GIS) software. The model is applied and validated with the landslides that occurred during the October 2019 Typhoon Hagibis in Marumori, Japan. The model results show good agreement with the reported time and depths of failure, and the analysis of the spatial distribution of predicted failures yielded receiver operating characteristic-area under the curve (ROC-AUC) value of 0.90. The applicability of the model can be extended for post-analysis, real-time, or projected assessment of slope stability, depending on the nature of input rainfall data (e.g., historical, real-time, forecast, hypothetical). [ABSTRACT FROM AUTHOR]

Massive quantities of alkaline rocks are excavated from urban coastal and mountain areas to make underground spaces available for infrastructure projects; however, such excavated rock often releases arsenic. In the present study, arsenic release from the excavated rocks with steel slag was investigated using dialysis and batch leaching tests to understand where arsenic is immobilized and which components in the steel slag suppress arsenic release from the excavated rock. Dialysis test indicated that the addition of steel slag at 10 wt% could suppress arsenic release at a level greater than 66%. The total arsenic content in the steel slag did not increase as compared with that before the test. Sequential extraction analysis indicated that the arsenic released during the dialysis test is mainly derived from arsenic fraction 1 (nonspecifically bound) due to the higher amount of this arsenic fraction in the excavated rock with the steel slag. Moreover, the steel slag extract could suppress arsenic release from the excavated rock and remove the arsenic from aqueous solution. The pH dependence test further indicated that the arsenic immobilized by the steel slag extract was stable under alkaline pH conditions. The levels of arsenic release decreased with increasing calcium release from the steel slag regardless of the type of excavated rock with an alkaline pH and were particularly seen at calcium released > 500 mg kg−1. These results indicate that the arsenic immobilization could be occurred not on the surface of steel slag, but on the excavated rock, and the calcium dissolved from the steel slag regulates the behavior of arsenic release from the surface of excavated rock. The findings of the present study suggest that the steel slag could be utilized to enable the reuse of excavated sedimentary and metamorphic rock of alkaline pH for the control of arsenic release. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to determine whether steel slag potentially could be utilized as an amendment for the reuse of excavated sedimentary rock naturally containing pyrite and the toxic metal cadmium. For this purpose, this study elucidated the mechanisms for simultaneous pH neutralization and cadmium immobilization of excavated sedimentary rock using steel slag under conditions of concurrent pyrite oxidation.Materials and methods: A batch leaching test was conducted using excavated sedimentary rock (mudstone) that was well mixed with steel slag in combinations ranging from 0 to 50 %wt to evaluate the relationship between the dosage of steel slag and both cadmium release and the pH value after 30 days of the treated rock. Another batch leaching test was performed using excavated sedimentary rock combined with steel slag from 0 to 1.5 %wt to monitor cadmium release and the pH as pyrite oxidation proceeded. Cadmium was sorbed onto the steel slag to evaluate cadmium sorption ability at pH values of 6.5 and 9.0. Using the cadmium-sorbed steel slag, the crystalline structure and the level of cadmium release from the steel slag at different pH values were determined.Results and discussion: The pH of excavated sedimentary rock without steel slag decreased, while that with more than 0.5 %wt steel slag remained within a neutral to alkaline pH range after 90 days, when potential pyrite oxidation was complete. The presence of steel slag did not inhibit the process of pyrite oxidation. These findings demonstrate that both pyrite oxidation and pH neutralization independently occurred in the excavated sedimentary rock, even in the presence of steel slag. The addition of more than 0.5 %wt steel slag maintained the level of cadmium released at less than 0.1 mg kg−1 throughout the 90-day period. The cadmium sorption test and X-ray diffraction analysis showed that cadmium immobilization using the steel slag was mainly governed by the (co)precipitation of carbonate minerals.Conclusions: This study indicates that an addition of 0.5 %wt steel slag to the excavated sedimentary rock can achieve pH neutralization and suppress cadmium release simultaneously, even with the occurrence of pyrite oxidation. Thus, this study suggests that steel slag potentially could be utilized as an amendment to allow the reuse of excavated sedimentary rock. [ABSTRACT FROM AUTHOR]

Post-earthquake debris flows that have occurred in Sichuan Province in southwestern China following the Wenchuan earthquake on May 12, 2008, have caused significant damage and casualties. Previous earthquake-induced landslides produced large amounts of loose material that remained on the steep slopes and in the gullies. As a consequence of heavy rainstorms during the rainy seasons, the existing loose material was transformed into numerous debris flows. Research has shown that the debris flows in the Wenchuan earthquake disaster areas have been characterized by their large scale, high speed, long run-out, and destructive impact. In order to identify the areas potentially at risk and to predict the flow severity, an accurate numerical method is needed to simulate these debris flows. In this paper, we have proposed a smoothed particle hydrodynamics (SPH) modeling technique-a meshfree particle method-to simulate the post-earthquake debris flows in the Wenchuan earthquake disaster areas. The SPH modeling technique introduces a Bingham model to analyze the relationship between material stress rates and particle motion velocity. Compared to traditional numerical methods, the SPH modeling technique is a true meshfree method of a pure Lagrangian nature. It can instantaneously track the motion of each particle, accurately predict the velocity, and naturally handle problems with extremely large deformations. In addition, the SPH method is based on continuum mechanics, and is therefore an efficient method to simulate large-scale debris flows. In this work, first, a viscoplastic fluid was simulated and verified with experimental results in order to evaluate the accuracy of the SPH model. Then propagation analysis of two typical post-earthquake debris flows in earthquake-hit areas was carried out, applying the SPH model. The simulation results showed good agreement with the limited field observation data. Our proposed SPH numerical modeling is able to capture the fundamental dynamic behavior of post-earthquake debris flows and can partially explain these complex phenomena. These simulation results can provide a preliminary scientific basis for hazard assessment and site selection for reconstruction in earthquake-prone areas. [ABSTRACT FROM AUTHOR]

Earthquakes can directly trigger multiple simultaneous slope failures in mountainous regions. Among these slope failures, flow-like landslides with high velocities and long run-outs can result in damage that is more destructive than other types of landslides. Timely and accurate recognition of the locations and magnitudes of flow-like landslides is essential for post-disaster relief. Synthetic aperture radar (SAR) sensors are suitable for deformation monitoring because of their capability to operate at day or night and in all weather conditions. Interferometric synthetic aperture radar (InSAR) is an advanced technique that extracts three-dimensional terrain and changes information from the radar images at a regional scale. The focus of this study is the Donghekou landslide-debris flow that was triggered by the 2008 Wenchuan earthquake. ALOS/PALSAR remote satellite images were interpreted by InSAR to generate digital surface elevation models. A comparison of data from a typical InSAR configuration with field survey data proves that the former is an effective method for rapidly detecting flow-like landslides in a mountainous area. The comparison also shows that the accuracy of the results is closely related to the correlation between the satellite radar images used, and further that the study accuracy would improve with the inclusion of better correlation. In this way, representations of pre- and post-landslide terrains could be generated for use in numerical simulations. The InSAR method has particular significance for areas without terrain data prior to slope failure, and can provide basic data for landslide hazard assessments. [ABSTRACT FROM AUTHOR]

Flowing sediments such as debris and liquefied soils could exert a tremendous amount of force as they impact objects along their paths. The total impact force generally varies with slope angle, velocity at impact, and thickness of the flowing sediment. Estimation of the impact force of flowing sediments against protective measures such as earth retaining structures is an important factor for risk assessment. In this paper, we conduct small-scale laboratory physical modeling of sand flow at different slopes and measure the impact force exerted by this material on a fixed rigid wall. We also conduct numerical simulations in the Eulerian framework using computational fluid dynamics algorithms to analyze and reproduce the laboratory test results. The numerical simulations take into consideration the overtopping of the wall with sand, which influenced the measured impact force–time history responses. In addition, the numerical simulations are shown to capture accurately the change of the impact force with slope angle. Finally, the modeling approach conducted in this study is used to estimate the quasi-static force generated by the sediment as it comes to rest on the wall following impact. [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: https://doi.org/10.1007/s10346-021-01642-4 [ABSTRACT FROM AUTHOR]

This study presents a method for constructing a surrogate localization model for a periodic microstructure, or equivalently, a unit cell, to efficiently perform micro-macro coupled analyses of hyperelastic composite materials. The offline process in this approach is to make a response data matrix that stores the microscopic stress distributions in response to various patterns of macroscopic deformation gradients, which is followed by the proper orthogonal decomposition (POD) of the matrix to construct a reduced order model (ROM) of the microscopic analysis (localization) with properly extracted POD bases. Then, response surfaces of the POD coefficients are constructed so that the ROM can be continuous with respect to the input datum, namely, the macroscopic deformation gradient. The novel contributions of this study are the application of the L2 regularization to the interpolation approximations of the POD coefficients by use of radial basis functions (RBFs) to make the response surfaces continuous and the combined use of the cross-validation and the Bayesian optimization to search for the optimal set of parameters in both the RBFs and L2regularization formula. The resulting model can be an alternative to microscopic finite element (FE) analyses in the conventional FE 2 method and realizes FE r with 1 < r < < 2 accordingly. Representative numerical examples of micro-macro coupled analysis with the FE r are presented to demonstrate the capability and promise of the surrogate localization model constructed with the proposed approach in comparison with the results with high-fidelity direct FE 2 . [ABSTRACT FROM AUTHOR]