Seismic activity often triggers liquefaction in sandy soils, which coupled with initial vertical tensile loads, poses a significant threat to the stability of suction bucket foundations for floating wind turbines. However, there remains a notable dearth of studies on the dynamic response of these foundations under combined seismic and vertical tensile loads. Therefore, this study developed a numerical method for analyzing the dynamic response of suction bucket foundations in sandy soils under such combined loading conditions. Through numerical simulations across various scenarios, this research investigates the influence of key factors such as seismic intensity, spectral characteristics, as well as the magnitude and direction of tensile loads on the seismic response of suction buckets. The results revealed that the strong earthquake may cause the suction bucket foundation of floating wind turbines to fail due to excessive vertical upward displacement. This can be attributed to that the accumulation of excess pore water pressure reduces the normal effective stress on the outer wall of bucket, and consequently decreases the frictional resistance of bucket-soil interface. Additionally, the above factors significantly influence both the vertical displacement of the suction bucket and the development of pore pressure in the surrounding soil. The findings can provide valuable insights for the seismic safety assessment of suction bucket foundations used in tension-leg floating wind turbines.

Three simplified models for the analytic determination of the dynamic response of a crossanisotropic poroelastic half-plane to a load moving with constant speed on its surface are presented and compared against the corresponding exact model. The method of analysis of the exact and approximate models uses complex Fourier series to expand the load and the displacement responses along the horizontal direction of the steady-state motion and thus reduces the partial differential equations of the problem to ordinary ones, which are easily solved. The three simplified models are characterized by reasonable simplifying assumptions, which reduce the complexity of the exact model and facilitate the solution. In the first simplified model all the terms of the equations of motion associated with fluid acceleration are neglected. In the second simplified model, solid displacements are assumed to be equal to the corresponding fluid ones, while the third simplified model is the second one corrected with respect to the fluid pressure at the free boundary (top) layer. All three simplified models are compared with respect to their accuracy against the exact model and the appropriate range of values of the various significant parameters of the problem, like porosity, permeability, anisotropy indices, or load speed, for obtaining approximate solutions as close to the exact solution as possible is thoroughly discussed.

Research on conductive models of damaged soil that consider the effect of microcrack expansion (the degree of saturation and suction) is weak. By assuming an equivalent conductive path a unit series-parallel conductive model of damaged soil under environmental loads was proposed. This model shows the change in soil porosity and fractal dimension. To verify that, the soil was damaged by rainfall cycles (simulated natural drying and rainfall). Electrical measurements and X-ray microscopy tests were performed to obtain the damaged soil resistivity, porosity, and fractal dimension variation. The resistivity was calculated based on the conductive model, and the error was approximately 7.9% compared with that of the test. In addition, the soil damage variable related to soil porosity and fractal dimension was introduced, and it exhibited a logarithmic relationship with soil resistivity. Variations in soil damage during the rainfall cycles were observed. In the top layer, the soil porosity increased and the fractal dimension decreased owing to microcrack expansion, resulting in an increase in soil damage. In contrast, in the bottom layer, the soil porosity decreased and the fractal dimension increased, resulting in a decrease in soil damage due to particle migration from the top area and pore fill.

This study investigates the underlying causes of pier displacement and cracking in a highway link bridge. The initial geological assessment ruled out slope instability as a contributing factor to pier movement. Subsequently, a comprehensive analysis, integrating in situ soil investigation and finite element modeling, was conducted to evaluate the influence of additional fill loads on the piers. The findings reveal that the additional filled soil loads were the primary driver of pier tilting and lateral displacement, leading to a significant risk of cracking, particularly in the mid- of the piers. Following the removal of the filled soil, visual inspection of the piers confirmed the development of circumferential cracks on the columns of Pier 7, with the crack distribution closely aligning with the high-risk zones predicted by the finite element analysis. To address the observed damage and residual displacement, a reinforcement strategy combining column strengthening and alignment correction was proposed and validated through load-bearing capacity calculations. This study not only provides a scientific basis for analyzing the causes of accidents and bridge reinforcement but, more importantly, it provides a systematic method for analyzing the impact of additional filled soil loads on bridge piers, offering guidance for accident analysis and risk assessment in similar engineering projects.

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.

This study introduces a novel methodology to address consolidation under long-term cyclic loading. The approach simplifies analysis by neglecting cyclic load induced fluctuations and by decomposing the cyclic load into a static load and a vibratory load without net tensile or compressive tendency over time. One-dimensional vibration consolidation tests are proposed to investigate the consolidation behavior of normally consolidated soil under vibratory loading. These tests yield a normal vibration consolidation line, which visually represents the consolidation effect of a given vibratory load on normally consolidated soil under different consolidation pressures. Based on these test results, a mathematical model is developed. This model incorporates a constitutive relationship that accounts for both the decrease in effective stress due to the structural damage caused by the vibratory load and the increase in effective stress due to the compression of the soil skeleton. The governing equation, with void ratio and effective stress as dependent variables, comprehensively describes the state change process of soil elements during vibration consolidation. Numerical solutions are then employed to analyze this process in detail.

Seismicity resulting from the near- or in-field fault activation significantly affects the stability of largescale underground caverns that are operating under high-stress conditions. A comprehensive scientific assessment of the operational safety of such caverns requires an in-depth understanding of the response characteristics of the rock mass subjected to dynamic disturbances. To address this issue, we conducted true triaxial modeling tests and dynamic numerical simulations on large underground caverns to investigate the impact of static stress levels, dynamic load parameters, and input directions on the response characteristics of the surrounding rock mass. The findings reveal that: (1) When subjected to identical incident stress waves and static loads, the surrounding rock mass exhibits the greatest stress response during horizontal incidence. When the incident direction is fixed, the mechanical response is more pronounced at the cavern wall parallel to the direction of dynamic loading. (2) A high initial static stress level specifically enhances the impact of dynamic loading. (3) The response of the surrounding rock mass is directly linked to the amplitude of the incident stress wave. High amplitude results in tensile damage in regions experiencing tensile stress concentration under static loading and shear damage in regions experiencing compressive stress concentration. These results have significant implications for the evaluation and prevention of dynamic disasters in the surrounding rock of underground caverns experiencing dynamic disturbances. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

This paper presents a comprehensive on-site decision-making framework for assessing the structural integrity of a jacket-type offshore platform in the Gulf of Mexico, installed at a water depth of 50 m. Six critical analyses-(i) static operation and storm, (ii) dynamic storm, (iii) strength-level seismic, (iv) seismic ductility (pushover), (v) maximum wave resistance (pushover), and (vi) spectral fatigue-are performed using SACS V16 software to capture both linear and nonlinear interactions among the soil, piles, and superstructure. The environmental conditions include multi-directional wind, waves, currents, and seismic loads. In the static linear analyses (i, ii, and iii), the overall results confirm that the unity checks (UCs) for structural members, tubular joints, and piles remain below allowable thresholds (UC < 1.0), thus meeting API RP 2A-WSD, AISC, IMCA, and Pemex P.2.0130.01-2015 standards for different load demands. However, these three analyses also show hydrostatic collapse due to water pressure on submerged elements, which is mitigated by installing stiffening rings in the tubular components. The dynamic analyses (ii and iii) reveal how generalized mass and mass participation factors influence structural behavior by generating various vibration modes with different periods. They also include a load comparison under different damping values, selecting the most unfavorable scenario. The nonlinear analyses (iv and v) provide collapse factors (Cr = 8.53 and RSR = 2.68) that exceed the minimum requirements; these analyses pinpoint the onset of plasticization in specific elements, identify their collapse mechanism, and illustrate corresponding load-displacement curves. Finally, spectral fatigue assessments indicate that most tubular joints meet or exceed their design life, except for one joint (node 370). This joint's service life extends from 9.3 years to 27.0 years by applying a burr grinding weld-profiling technique, making it compliant with the fatigue criteria. By systematically combining linear, nonlinear, and fatigue-based analyses, the proposed framework enables robust multi-hazard verification of marine platforms. It provides operators and engineers with clear strategies for reinforcing existing structures and guiding future developments to ensure safe long-term performance.

To quantify the influence of basic physical properties and cyclic loading conditions on the liquefaction properties of sandy soils, this study uses a combination of physical experiments and numerical simulations to investigate the liquefaction behavior of saturated sandy soils under undrained conditions and their relationship to physical property parameters and external loads. A numerical model with discrete elements was created based on cyclic triaxial tests. A numerical study and predictive analysis of liquefaction of common bulk samples were carried out in conjunction with a PSO-BP neural network prediction model. Using a multivariate analysis of variance and a random forest model, the complexity of the influence of physical parameters and external loads on soil liquefaction was investigated. Quantitative results indicate that particle size distribution, external loads and effective internal friction angle have a significant influence on the liquefaction of saturated sandy soils. In summary, the results of this study provide new insights into understanding the liquefaction behavior of sandy soils.

This paper presents an upgraded nonlinear creep consolidation model for VDI soft ground, incorporating a modified UH relation to capture soil creep deformation. Key novelties also include considering linear construction loads, TDP boundary conditions, and Swartzendruber's flow in the small strain consolidation domain. The system was solved using the implicit finite difference method, and numerical solutions were rigorously validated. A parametric analysis reveals that soil viscosity causes abnormal EPP increases under poor drainage conditions during early consolidation. Meanwhile, neglecting the time effect of the secondary consolidation coefficient delayed the overall EPP dissipation process and overestimated the settlement during the middle and late consolidation stages. Furthermore, TDP boundaries, Swartzendruber's flow, and construction processes significantly influence the creep consolidation process but not the final settlement. These findings offer fresh insights into the nonlinear creep consolidation of VDI soft ground, advancing the field.