Search Results (28)

Landslide impacts into water generate impulse waves that, in confined basins and along steep coasts, escalate swiftly into hazardous near-shore surges. In this study, we present a scenario-aware workflow using gradient boosting and k-means clustering, and explain them using Shapley additive explanations (SHAPs). Two cases are addressed: forecasting at water entry (Scenario I) with predictors Froude number $Fr$, relative effective mass M, and relative thickness S; and pre-event assessment (Scenario II) with predictors Bingham number $Bi$, relative moving length L, and relative initial mass $Mi$. Using 270 controlled physical-model experiments, we benchmark six learning algorithms under 5-fold cross-validation. Gradient boosting delivers the best overall accuracy and cross-scenario robustness, with XGBoost close behind. Scenario I attains a coefficient of determination $R^2$ of 0.941, while Scenario II achieves $R^2=0.865$. Residual analyses indicate narrower spreads and lighter tails for the top models. SHAP reveals physics-consistent controls: M and $Fr$ dominate Scenario I, whereas initial mass and the $Bi$ dominate Scenario II; interactions $Fr\times S$ and $Mi\times Bi$ clarify non-linear amplification of wave amplitude and height. The cluster–predict–explain framework couples predictive skill with physical transparency and is directly applicable to coastal hazard screening and integration into shoreline early-warning workflows. Full article

Harmonic summation and amplification by winds blowing contrary to currents are known contributions to rogue waves in the region of the Agulhas current, but the causes of the observed wave steepness, asymmetric form, and non-breaking are poorly understood. The potential effect of bathymetric and meteorological features has not been addressed. Vortex theory was applied to develop a theory of wave formation, based on conceptual reasoning. Rogue wave formation is attributed to the following: (1) wind lee vortices causing steepening of a wave’s leeward face, and suppressing wave breaking; (2) boundary layer vortices from the meteorological cold front transferring energy to the wind lee vortices thereby sharpening the wave; (3) Agulhas current boundary layer vortices interacting with water lee vortices to accelerate a jet of water between them, thereby steepening the wave and enhancing the preceding trough; (4) bathymetric topology, especially a canyon on the continental slope, generating a vortex in the Agulhas current. This vortex is detached from the canyon by prising of the coastal downwelling current (induced by the meteorological cold front) and combines with the water lee vortex to heighten the wave, and (5) jetting, which arises when the canyon vortex and the Agulhas current boundary layer vortices pass each other, thereby accentuating wave height, steepness, and asymmetry. Full article

As a key transportation infrastructure, it is of great significance to ensure the seismic safety of the high-speed railway hub station. Taking Changde high-speed railway hub station as background, a comprehensive 3D numerical model of the high-speed railway station structure is proposed to consider the engineering geological characteristics of the site, soil nonlinearity, and pile-soil interactions. The results show that the hub station structural system, considering pile-soil interaction, presents the ‘soft-upper-rigid-down’ characteristics as a whole, and the natural vibration is lower than that of the station structure with a rigid foundation assumption. Under the action of three strong seismic motions, the nonlinear site seismic effect is significant, the surface acceleration is significantly enlarged, and decreases with the buried depth. The interaction between pile and soil is related to the nonlinear seismic effect of the site, which deforms together to resist the foundation deformation caused by the strong earthquake motions, and the depth range affected by the interaction between the two increases with the increase of the intensity of earthquake motion. Among the three kinds of input earthquake motions, the predominant frequency of the Kobe earthquake is the closest to the natural vibration of the station structure system, followed by the El Centro earthquake. Moreover, the structures above the foundation of the high-speed railway hub station structural system are more sensitive to the spectral characteristics of Taft waves and El Centro waves compared to the site soil. This is also the main innovation point of this study. The existence of the roof leads to the gradual amplification of the seismic response of the station frame structure with height, and the seismic response amplification at the connection between the roof and the frame structure is the largest. The maximum story drift angle at the top floor of the station structure is also greater than that at the bottom floor. Full article

During a seismic movement, each wave field incoming to a foundation by reflecting from the surroundings causes amplification. Therefore, the seismic response of any building is affected by both the topography and the adjacent building. In this study, the effect of the adjacent building on the seismic performance of a building located near a shallow slope is numerically assessed. In the adopted three-dimensional finite element simulation, nonlinear variation of soil stiffness and hysteretic damping, elastoplastic behaviour of the superstructure frame system showing significant deviations from linear behaviour beyond the limits of elastic behaviour and varying distances between the foundation edge and the adjacent building were employed. Two identical 10-storey moment-resisting buildings, 40 m thick dense clayey sand, and a 5 m high shallow slope were considered as a reference model and simulated using the direct method in the time domain. The seismic performance of the building was studied at a distance equal to the height of the slope from the crest. The results of the analyses represent an interaction in which both shallow slope and adjacent building effects are observed together. Incremental structure–soil–structure interaction effect, on the one hand, created additional shear stresses on the shallow slope and enhanced the foundation rocking of the building. On the other hand, as a natural result of dynamic cross-interaction, it resulted in a reduction in the maximum acceleration value captured at the foundation, a drop in the base shear demand, and a large change in the maximum storey displacements at the lower floors. As a result of these cases, storey drifts increased. The results highlighted that the structure–soil–structure interaction cannot be neglected in the presence of a slope. Full article

The conversion of abandoned butted well salt cavities into underground storage facilities holds immense significance for safeguarding energy security and improving the ecological environment. A significant barrier to the reconstruction of these old cavities is the limited comprehension of their complete morphology, caused by residue coverage. The three-dimensional seismic techniques excel in identifying complex geological structures but have a limited understanding of underground old salt cavity morphology, thus the seismic forward simulation method is utilized to study their seismic response patterns. Based on 3D seismic data, well logging data, and measured cavity shape parameters from the Yexian salt mine region in Henan Province, China, a geological model and observation system were established. The seismic response characteristics of the butted well salt cavern model, encompassing five distinct morphological attributes such as cavity spacing, cavity diameter, cavity height, sediment height, and horizontal connection channel height, were thoroughly investigated. The findings show that the cavity roof exhibits a distinctive “two peaks sandwiching a strong valley” feature, with the positions of the valley and roof remaining aligned and serving as a reliable indicator for identifying the cavity’s top surface. The width of the roof waveform exhibits an exponential amplification effect relative to the cavern width. The residue’s top surface presents an “upward-opening arc” wave peak with a downward shift that diminishes as the residue’s height increases. This peak forms a circular feature with the cavity roof reflection waveform, and the residue’s top surface is always located in the upper half of this circular waveform. The horizontal connection channel’s top and bottom surfaces exhibit contrasting reflection patterns, with the top position aligning with the reflection trough and the bottom reflection waveform shifting downward as the channel height increases. The brine cavern, residue, and bottom of the salt cavern mainly exhibit chaotic reflections. There are distinct identification characteristics on the cavity top, residue top, and connecting channel top in forward simulation. The research findings provide valuable guidance for identifying the morphology of the underground real butted well salt cavity based on 3D seismic data and accelerating the construction of underground energy storage facilities. Full article

The suction bucket foundation equipped for offshore wind turbines was a promising solution for sandy seabed locations. However, its typically short embedment depth presented additional challenges when installed in seismic zones. These challenges pertained not only to structural response but also to the seismic motion itself, which was strongly influenced by soil characteristics. This study examined the uncertainty of equivalent shear-wave velocities to explore the variability in input seismic motion characteristics and investigated their impact on the structural response in terms of tower-top displacement, mudline displacement, and acceleration amplification factor at the hub height of 3 MW and 5.5 MW suction bucket-supported offshore wind turbines (OWTs). Additionally, the influence of equivalent shear-wave velocities on the exceedance probabilities of various damage states, using fragility curves for tower-top and mudline displacement, was analyzed. The results indicated that equivalent shear velocities of soil significantly impacted the seismic performance of suction bucket-supported offshore wind turbines. These effects were closely related to the intensity of the seismic motion, highlighting the importance of carefully considering the correlation between site-specific shear velocities and earthquake intensities. Full article

CFD-based numerical wave tank models are valuable tools for analyzing the nonlinear interaction between waves and structures. This paper aims to examine the deformation of high-order free surfaces near a vertical, surface-piercing fixed cylinder with various cross-sections under regular head waves, assuming no wave breaking. Additionally, the study investigates the effects of wavelength on wave evolution, nonlinear wave amplification, and the harmonics around the cylinder. The numerical analysis is performed using the CFD toolbox OpenFOAM. The comparison of numerical results for different cross-sections reveals the influence of corner ratio on lateral edge waves and highlights its significant impact on the nonlinear wave field around the cylinder, particularly for short incident waves. The numerical results indicate the important contribution of the cross-section shape together with the corner effect on the lateral edge waves and accordingly the nonlinear wave field surrounding the given column, which involves high harmonics wave amplification up to fourth. The reduction in corner ratio results in a reduction in maximum run-up height from 2.57 to 2.2 in short waves, while for the long waves, it is from 1.61 to 1.45. This research not only enhances our understanding of fluid–structure interactions but also has implications for the design and safety of hydrogen storage and transportation systems. Understanding dynamic pressures and structural responses is crucial for these applications. CFD simulations of wave–cylinder interactions are essential for designing and optimizing offshore hydrogen infrastructure. These simulations model how waves interact with cylindrical structures, such as wind turbine foundations, hydrogen production platforms, and storage tanks. Understanding these interactions is vital for ensuring the structural integrity, efficiency, and sustainability of offshore hydrogen facilities. Full article

Numerical simulations were generated to investigate the response of a very large floating airport to an airplane takeoff, using the set of nonlinear shallow water equations of velocity potential for water waves interacting with a floating thin plate. We have proposed two methods to reduce persistent airport vibration: reflectance reduction by decreasing the flexural rigidity in airport edge parts and amplification reduction by decreasing the still water depth partially under airport runways. First, when the flexural rigidity is uniformly decreased in an airport edge part, the reflectance of the floating body waves due to a B737 was reduced because of the multiple reflections. However, the wave reflectance for a B747 increased, depending on the conditions. A too-long edge part was not effective in reducing the wave reflectance. Conversely, when the flexural rigidity is linearly decreased in an airport edge part, the wave reflectance was reduced for both airplanes. Second, when the still water depth under an airport runway is partially reduced at the location where floating body waves are amplified, the wave heights of floating body waves tended to decrease as the still water depth in the shallower area decreased. Full article

Earthquakes are one of the main causes of bedding slope instability, and scientifically and quantitively evaluating seismic stability is of great significance for preventing landslide disasters. This study aims to assess the bedding slope stability under seismic loading and the influences of various parameters on stability using a pseudo-dynamic method. Based on the limit equilibrium theory, a general solution for the dynamic safety factor of bedding slope is proposed. The effects of parameters such as slope height, slope angle, cohesion, internal friction angle, vibration time, shear wave velocity, seismic acceleration coefficient, and amplification factor on stability are discussed in detail. To evaluate the validity of the pseudo-dynamic solution, the safety factors are compared with those given by early cases, and the results show that the safety factors calculated by the present formulation coincide better with those of previous methods. Moreover, a two-dimensional numerical solution of bedding slope based on Mohr–Coulomb’s elastic–plastic failure criterion is also performed by using the finite element procedure, and the minimum safety factor is essentially consistent with the result of the pseudo-dynamic method. It is proved that the pseudo-dynamic method is effective for bedding slope stability analyses during earthquakes, and it can overcome the limitations of the pseudo-static method. Full article

The southwestern region of China is close to the Eurasian earthquake zone. Many engineering areas in southwestern China are affected by earthquakes and are close to the epicenter of earthquakes that occur in this region. During earthquakes, slopes with weak interlayers are more likely to cause large-scale landslides. In response to the low stability of slopes with weak interlayers in reservoir dam areas, the dynamic response law and failure mechanism of weak interlayered slopes under the combined action of reservoir water and seismic forces were studied through shaking table model tests and finite element numerical simulation software. The height of the water level and the size of the seismic waves were changed during these tests. The research results indicate that seismic waves are influenced by weak interlayers and are repeatedly superimposed between the weak interlayers and the slope surface, resulting in an acceleration amplification effect that increases by approximately 1.8 times compared to homogeneous slopes. Vertical earthquakes have a significant impact on the dynamic response of slopes, and their peak acceleration amplification coefficient can reach 0.83 times the horizontal peak acceleration. The stability of weak interlayers during earthquakes is the worst within the range of the direct action of reservoir water. The failure mode of a slope is as follows: earthquake action causes cracking in the upper part of the slope, and as the earthquake increases in intensity, and the infiltration of reservoir water intensifies, the cracks expand. The soft and muddy interlayer in the front section of the slope forms a sliding surface, and ultimately, the sliding failure forms an accumulation body at the foot of the slope. In reservoir dam areas, the stability of a slope is closely related to the engineering safety of the reservoir dam. Therefore, when a strong earthquake and the water level in a reservoir jointly affect a weak-interlayer slope, the slope is in the stage of plastic deformation and instability. The stability of the slope may be overestimated, and the slope is likely vulnerable to sliding instability, which needs to be monitored and treated. Full article

The dynamic response characteristics of a two-dimensional submerged floating tunnel (SFT) under random and freak waves were investigated in the present study. The results demonstrate that (1) the dynamic responses of the SFT under the freak wave are significantly larger than those under the largest wave in the wave train excluding the freak wave, particularly for the motion response. The maximum values of the motion responses induced by the freak wave were several times larger than those induced by the largest wave in the wave train excluding the freak wave, far exceeding the proportion of the corresponding wave height. (2) The freak wave parameter α₁ has a significant effect on the amplification coefficients of surge, heave and pitch; all increase nonlinearly as α₁ increases. Within α₁ = 1.90~2.59, the amplification coefficients of the surge, heave and pitch vary in the ranges of 1.91~6.46, 1.53~3.87 and 1.73~5.32, respectively. (3) Amplification coefficients of tension increase almost linearly as α₁ increases. Additionally, the amplification effect of the freak wave on the mooring tension is much smaller than that on motion responses. Within α₁ = 1.90~2.59, the amplification coefficients of tension vary from 1.15 to 1.35. (4) Generalised amplification coefficients of motion responses increase as α₁ increases and are all greater than 1.0, indicating that growth rates for motion responses under the freak wave exceed the growth rates for maximum wave height. Moreover, motion responses show a significantly nonlinear growth as maximum wave height increases. The generalised amplification coefficients of the mooring tension decrease as α₁ increases, and are all less than 1.0, indicating that the dynamic amplification effect of the freak wave on the mooring tension is much smaller than that on motions. On the other hand, growth rates of the mooring tension under freak waves are smaller than the linear growth rate of the height of freak waves. Full article

Numerical simulations were generated to investigate the response of a floating airport to airplane movement using the nonlinear shallow water equations of velocity potential for water waves interacting with a floating thin plate. First, in the 1D calculations, the airplanes were B747 and B737. At touch-and-go, when the airplane speed is closer to the water wave speed, even B737 produced large waves based on the resonance. The impacts due to both the touchdown and leaving of the airplanes generated other forward and backward waves. At landing, when the airplane speed approached the water wave speed, a forced wave was generated and amplified, with many free waves ahead. At takeoff, a wave clump, generated shortly after starting to run, propagated in front of the airplanes. Although the wave height increased from superposition with the reflected waves, the wave reflectance was reduced by lowering the flexural rigidity near the airport edge. Second, in the 2D calculations, B787 performed landing and takeoff. When the still water depth is shallower, a grid-like pattern was formed at the floating airport and appeared more remarkably in landing than in takeoff. The effective amplification occurred from a sufficient load applied when the airplane speed approached the water wave speed. Furthermore, the maximum upslope gradient beneath the airplane increased as the still water depth decreased, and it was larger in takeoff than in landing. Full article

Fluid resonance may occur in a narrow gap between two side-by-side vessels under wave actions, which can cause significant wave height amplification inside the gap and further induce large wave loads and motion responses of the vessel. Based on an open-sourced computational fluid dynamics (CFD) package, OpenFOAM, the steady-state gap resonance phenomenon formed in between two side-by-side boxes and triggered by the incident regular waves is simulated, where the upriver box keeps fixed and the downriver one heaves freely under wave actions. This article comprehensively investigates the influence of the vertical degree of freedom of the downriver box on the wave loads exerting on both boxes and further reveals how the relative position of the heaving box with respect to the incident wave direction affects the characteristics of wave loads during the steady-state gap resonance. The results show that both the normalized largest wave loads and the dimensionless wavenumber where the normalized largest wave loads occur are significantly affected by both the incident wave heights and the relative position of the heaving box to the incident wave direction. Full article

The jacket is the most widely-used fixed foundation for offshore wind turbines due to its superior strength and low installation cost in relatively deep waters. Floating crane vessels are commonly used to install jacket foundations. However, the dynamic coupling between the jacket and the floating vessel might generate complex dynamic responses under wave action. The complexity of the multi-body system requires comprehensive time-domain simulations and statistical analysis to obtain reliable results, especially for the evaluation of the operational safety of offshore lift installations of a jacket foundation. In this context, this study performs numerical simulations and statistical analyses to predict the extreme responses and the preliminary allowable sea states for guiding the lowering operation of a jacket using a floating crane vessel. First, ANSYS-AQWA is used to obtain the hydrodynamic coefficients of the vessel in the frequency domain. A nonstationary time-domain simulation of jacket lowering with winches is performed to identify several preliminary critical vertical positions of the jacket from the time series in an irregular wave. The extreme responses of a target probability are evaluated by the extreme distribution model after a large number of steady-state time-domain simulations of the critical vertical positions in irregular waves. The most critical vertical position is determined from three preliminary critical vertical positions by comparing the extreme responses. Eigenvalue analysis and spectrum analysis of the most critical vertical position of the jacket are carried out to find the natural periods of the system and the dynamic coupling characteristics between different components. The influence of wave direction, significant wave height, and spectrum peak period on the dynamic responses are also analyzed in the most critical vertical position. Furthermore, the optimal wave direction is determined as the head sea. Preliminary allowable sea states are derived by comparing the calculated dynamic amplification coefficient with the defined operational criteria. Full article

The Akhmediev breather (AB) solution of the nonlinear Schrödinger equation (NLSE) shows that the maximum crest height of modulated wave trains reaches triple the initial amplitude as a consequence of nonlinear long-term evolution. Several fully nonlinear numerical studies have indicated that the amplification can exceed 3, but its physical mechanism has not been clarified. This study shows that spectral broadening, bound-wave production, and phase convergence are essential to crest enhancement beyond the AB solution. The free-wave spectrum of modulated wave trains broadens owing to nonlinear quasi-resonant interaction. This enhances bound-wave production at high wavenumbers. The phases of all the wave components nearly coincide at peak modulation and enhance amplification. This study found that the phase convergence observed in linear-focusing waves can also occur due to nonlinear wave evolution. These findings are obtained by numerically investigating the modulated wave trains using the higher-order spectral method (HOSM) up to the fifth order, which allows investigations of nonlinearity and spectral bandwidth beyond the NLSE framework. Moreover, the crest enhancement is confirmed through a tank experiment wherein waves are generated in the transition region from non-breaking to breaking. Owing to strong nonlinearity, the maximum crest height observed in the tank begins to exceed the HOSM prediction at an initial wave steepness of 0.10. Full article