This paper proposes a frequency wavenumber-finite element hybrid method with kinetic source model for dynamic analysis of pile founded nuclear island from fault to structure. This method benefits from the effective synthesis of broadband ground motions by the fault source model, the realism of frequency wavenumber for earthquake simulation from fault to the site and the mesh refinement capabilities of the finite element in modeling the nuclear structure and the near soil. This method achieves the expression of source rupture, wave propagation, site response, soil-structure interaction, soil nonlinearity and structure response accurately, which solves the multi-scale problem from crustal layer to nuclear structure. Under finite-fault excitation, the correctness of the proposed method is validated by comparing with the frequency wavenumber method. Then, a full process seismic simulation of a pile founded nuclear island built on a non-rock site is conducted. The influence of source parameter and soil-structure interaction is studied. Results indicate that the change of source parameter can lead to difference nuclear island failure direction. With the increase of dip angle, the appearance of maximum stress is in advance. The soil nonlinearity could greatly amplify the soil-structure interaction effect and the loads on piles. The connection between the containment vessel and the raft is vulnerable and the piles on the edge of the raft is prone to damage. This hybrid method could accomplish an appropriate seismic evaluation of the nuclear structures and the conclusions may provide reference for seismic design of nuclear structure.

As the monopile supported offshore wind turbine (OWT) is a dynamic sensitive structure, one of the major challenges in its design is the assessment of the natural frequency to avoid resonance during the lifetime. Since the characteristics of OWTs under dynamic loading and their long-term behavior are not fully understood, to study their natural frequency considering soil-monopile interaction, a series of scaled model tests in sand were performed. The first part was about the initial resonant frequency subjected to different forcing amplitudes and the second part was about the change of the natural frequency under long-term horizontal cyclic loadings. Based on the test results, the effects of pile-soil interaction, related to the loading amplitude, embedment depth, soil density, and cyclic numbers, on the natural frequency of OWTs are presented by a non-dimensional group based on the explanation of the governing mechanism. As the soil nonlinearity leads to a degradation in the natural frequency of monopile supported OWTs in the sand and the cyclic loading results in an increase, the choice of the natural frequency closer to the upper limit of the 1P band is suggested in practice based on the tradeoff of the two above effects.

This work proposes a novel plastic damage model to capture the post elastic flow-controlled damages in pavement-soil systems prescribed by the vibrations of moving load. Initially, the pavement structure has been modelled as a single-layer system resting on a spring-dashpot system representing soil mass. Then, multilayer modelling was adopted to analyze the post-elastic dynamic response in supporting plastic flow-controlled layers of geomaterial. Three mechanistic zones namely, elastic recoverable, transition, and post elastic zone have been conceptualized to identify the damage. The nonlinearity in stress and equivalent plastic strain has been observed for the set of selected velocities and load intensities specified in codal provisions. The variation in equivalent plastic strain is observed in the range of 10-16 to 10-3% in the granular base layer and 10-16 to 10-4% in the subgrade soil layer. The findings show that the equivalent plastic strain due to plastic flow prescribed by the vibrations of moving action of vehicular load at varied velocities is one of the root causes of permanent deformations. The propagation of dynamic load vibrations from the uppermost layer of pavement induces the generation of stress waves within distinct sub-layers of geomaterial. Hence, the observed behaviour leads to the generation of nonlinear stress waves prescribed by a vibrational mechanism of stress transfer (VMST). Therefore, the evaluation of the nonlinearities causing damage in pavement structure supported by flow controlled geomaterials has the potential to predict permanent deformations and its implications in the design of pavements supporting the transportation network.

The impact of site effects on ground motion is a critical factor for earthquake disaster prevention and mitigation, as these effects can amplify ground motion and affect building fragility. On February 6, 2023, southeastern Turkey was struck by two strong earthquakes, with magnitudes of Mw7.7 and Mw7.6, followed by numerous aftershocks. These events resulted in severe casualties and substantial economic losses. Field investigations revealed severe damage to mid-rise and high-rise buildings in Kahramanmara & scedil; and Antakya. Both cities are located in valley regions, which are particularly susceptible to earthquake damage due to the amplification of ground motion caused by soft soil conditions and valley topography. In this paper, Horizontal-to-Vertical Spectral Ratio (H/V) technique is used to decipher how site effects affect ground motion and damage using the strong motion records. The analysis revealed that the predominant frequency of ground motion decreases near the valley areas and increases toward the hill slopes. These spatial variations in predominant frequency have significant implications for building safety. Structures located in areas where the predominant frequency matches their natural frequency are more prone to resonance effects, significantly increasing the risk of damage during seismic events. Additionally, the study found that the nonlinearity of the site conditions amplified the acceleration response spectrum at a period of 1 s. This amplification exceeded the local structural design capacity. The findings indicate that site effects can significantly intensify earthquake damage in Kahramanmara & scedil; and Antakya by amplifying ground motion and increasing the vulnerability of mid-rise and high-rise structures.

Shallow failures often occur in earthen sites. The nonlinear strength criteria of silt and their correlation with dry-wet cycles are necessary for evaluation of failure problems of earthen site exposed to natural environments, such as rainfall and evaporation. Thus, in this study, a designed soil column and method in line with the natural environment characteristics of earthen sites were adopted to study the effects of the number of dry-wet cycles on the shear mechanical properties of the site silt under consolidated undrained triaxial conditions. The results show that the strength of silt and its parameter, cohesion c, do not monotonically decrease with the number of dry-wet cycles but exhibit a trend of initially increasing and then decreasing. The nonlinear characteristics of the strength of silt are remarkable, particularly in the range of small normal stresses. Based on Baker's generalized power law strength criterion, a nonlinear strength criterion considering the number of dry-wet cycles of silt was established with the parameter A of the strength criterion initially increasing and gradually decreasing and the value of N essentially unchanged. The improved Duncan-Chang model considering the dry-wet cycle effect and strength nonlinearity of silt in earthen sites was presented and verified. The research can offer significant theoretical support for the analyses of shallow collapses and other issues related to failure problems of earthen sites.

Expansive soils pose significant challenges due to their tendency to swell when wet and shrink when dry, causing ground instability. These volumetric changes can lead to structural damage, including foundation cracks, uneven floors, and compromised infrastructure. Addressing these issues requires proper soil evaluation and the implementation of stabilization techniques to ensure long-term safety and durability. The high degree of expansive, problematic soil is stabilized by cement, bitumen, lime, etc. This investigation predicts the unconfined compressive strength (UCS) of lime-treated soil using decision tree (DT), ensemble tree (ET), gaussian process regression (GPR), support vector machine (SVM), and multilinear regression (MLR). This research investigates the impact of dimensionality on the computational approaches. The variance accounted for (VAF), correlation coefficient (R), mean absolute error (MAE), root mean square error (RMSE), and performance index (PI) metrics have computed the model's performance. The comparison reveals that model ET5 has predicted UCS with an excellent performance in testing (RMSE = 368.06 kPa, R = 0.9640, VAF = 91.60, PI = 1.8077) and validation (RMSE = 508.41 kPa, R = 0.9165, VAF = 83.89, PI = 1.6337) phase. Also, model ET5 has achieved better score (total = 90), area over the curve (testing = 8.98E-04, validation = 1.56E-03), computational cost (testing = 0.1772s, validation = 0.1551 s), uncertainty rank (= 1), and overfitting (testing = 2.32, validation = 2.80), presenting model ET5 as an optimal performance model. The dimensionality analysis reveals that simple models like MLR, SVM, GPR, and DT struggle with high-dimensional data (case 5). Still, the ET5 model achieves high performance and reliable prediction with consistency, compaction and soil physical parameters. Conversely, the effect of multicollinearity has been observed on the performance of the MLR, SVM, and DT models.

Understanding the shear behaviors of expansive soils under a wide range of confining pressures 6 3 is crucial for effectively managing their shallow hazards, especially at low 6 3 values. The shear behaviors of expansive soils under the low 6 3 values exhibit significant differences with those under the high 6 3 values, which have been inadequately addressed in existing research. This paper investigated the shear behaviors of two expansive soils across a wide range of 6 3 values (i.e., 15-400 kPa) through consolidated undrained triaxial tests. The results showed a significant nonlinear relationship between the shear strength and 6 3 , particularly at the low 6 3 values. The nonlinearity of shear strength versus 6 3 in shallow expansive soils was described by a modified power function. As 6 3 decreased, both the brittleness index 7 and curvature K increased nonlinearly. Comparisons between the tangent method, based on the modified power function, and the K f method, based on the Mohr- Coulomb criterion, suggested that neglecting the nonlinearity of shear strength versus 6 3 led to overestimations of the cohesion and underestimations of the internal friction angle at low 6 3 values, and the reverse trend was observed at high 6 3 values. The magnitude of these deviations depended on both the shear strength nonlinearity and the selected 6 3 values. The findings presented herein are helpful for the mitigation of shallow hazards in roadbeds, slopes, and foundation engineering associated with expansive soils.

This study established a numerical model for soil-structure interaction (SSI) to examine the effects of the spatial incidence angle of SV waves and soil nonlinearity, utilizing viscoelastic artificial boundaries (VAB) and equivalent nodal force (ENF) method. Both the foundation's and superstructure's torsion and rocking responses were then analyzed. The findings indicate that subjected to spatially oblique incident SV waves, the rectangular foundation primarily has the rocking response while the torsional response is negligible. Furthermore, the maximum torsional and rocking angles about the x-axis at each frame floor are significantly enlarged by comparison with the perpendicular incident case. Moreover, the soil nonlinearity could increase the foundation's rocking angle and enlarge the maximum torsion and rocking responses of the structure's floors. Consequently, structural seismic damage assessment requires considering both the soil nonlinearity and incident seismic wave angles.

In soil mechanics, liquefaction is the phenomenon that occurs when saturated, cohesionless soils temporarily lose their strength and stiffness under cyclic loading shaking or earthquake. The present work introduces an optimal performance model by comparing two baselines, thirty tree-based, thirty support vector classifier-based, and fifteen neural network-based models in assessing the liquefaction potential. One hundred and seventy cone penetration test results (liquefied and non-liquefied) have been compiled from the literature for this aim. Earthquake magnitude, vertical-effective stress, mean grain size, cone tip resistance, and peak ground acceleration parameters have been used as input parameters to predict the soil liquefaction potential for the first time. Performance metrics, accuracy, an area under the curve (AUC), precision, recall, and F1 score have measured the training and testing performances. The comparison of performance metrics reveals that the model Runge-Kutta optimized extreme gradient boosting (RUN_XGB) has assessed the liquefaction potential with an overall accuracy of 99%, AUC of 0.99, precision of 0.99, recall value of 1, and F1 score of 1. Moreover, model RUN_XGB has a true negative rate of 0.98, negative predictive value of 1, Matthews correlation coefficient of 0.98, and average classification accuracy of 0.99, close to the ideal values and presents the robustness of the RUN_XGB model. Finally, the RUN_XGB model has been recognized as an optimal performance model for predicting the liquefaction potential. It has been noted that a low multicollinearity level affects the prediction accuracy of models based on conventional soft computing techniques, i.e., logistic regression. This research will help researchers choose suitable hybrid algorithms and enhance the accuracy of seismic soil liquefaction potential models.

Shallow sediments can respond non-linearly to large dynamic strains and undergo a subsequent healing phase as the material gradually recovers following the passing of seismic waves. This study focuses on the physical changes in the subsurface caused by the shaking from a buried chemical explosion detonated in a borehole in Nevada, USA, as a part of the Source Physics Experiment Phase II. The explosion damaged the shallow subsurface and modified the frequency content recorded by 491 geophones and 2240 Distributed Acoustic Sensing (DAS) channels within 2.5 km from surface ground zero. We observe a gradual shift of resonance frequencies in the 10-25 Hz frequency band in the hours following the explosion and develop a method to characterize the related logarithm-type healing process of the shallow (i.e., upper similar to 25 m) subsurface. We find that stronger levels of ground motion increase the relative degree of damage and duration of the subsurface healing; with the spall region exhibiting the largest degree of damage and longest healing recovery time. We observe coherent spatial patterns of damage with the region located to the southeast of the explosion exhibiting more damage than the southwest region. This study demonstrates that both DAS and co-located geophones capture similar temporal changes associated with the physical processes occurring in the subsurface, with the high-density sampling of DAS measurements enabling a new capability to monitor the fine-scale changes of the Earth's shallow subsurface following the detonation of a buried explosion. Strong seismic waves can damage the soft sediments that compose the shallow layers of the ground. A healing phase of the sediments generally follows the passing of the seismic waves as the medium gradually recovers with time. We study the spatio-temporal response of the subsurface in the vicinity of a large buried chemical explosion that was detonated in a borehole at the Nevada National Security Site, USA. The explosion, which was part of the Source Physics Experiment Phase II, was well instrumented along a surface fiber-optic cable with Distributed Acoustic Sensing (DAS) and hundreds of geophones. We find that the explosion, which generated a spallation of the shallow Earth, primarily damaged the upper similar to 25 m of the subsurface. We characterize the healing of the sediments and find a correlation between the duration of the healing phase and the level of maximum shaking. The high density of sensors also allows us to study spatial variations in the response of the shallow subsurface. This study demonstrates that both DAS and geophone continuous data similarly capture the spatio-temporal variations of the Earth's physical properties following strong ground motions, with DAS enabling meter-scale measurements of the subsurface changes. Shallow subsurface damage and subsequent healing caused by a buried chemical explosion are constrained with DAS and geophone data The explosion caused a relative drop of the average S-wave velocity in the Earth's shallow layers of a few percents The logarithm-type healing process of the subsurface exhibit a longer duration within the spall region