Wave propagation in an ocean site is an essential research topic in various scientific fields, such as offshore geotechnical engineering, ocean seismology, and underwater acoustics. Previous studies have considered the seabed soil as elastic or poroelastic, ignoring the viscoelastic characteristics of its solid skeleton. Based on the fractional-derivative viscoelastic theory and the modified Biot theory, considering the flow-independent viscosity related to solid skeleton, this paper proposes a generalized viscoelastic wave equation for a fluid-saturated porous medium. The equation has a flexible mathematical form to describe soil rheological properties more accurately through fractional order. On this basis, the total wave field equation of an ocean site, modeled as the fluid-poroviscoelastic-solid media, is established. Then an analytical solution for wave propagation in an ocean site subjected to obliquely incident P and SV waves is obtained, and its degeneration and extension are studied. The proposed method is comprehensively validated through experiment, analytical, and numerical methods. Finally, a parameter analysis is performed to investigate the effects of water depth, seabed properties (including viscoelastic parameters, fractional order and permeability), and incident angle on the seismic response of a poroviscoelastic seabed.

In the numerical simulation of wave problems, it is often necessary to truncate the unbounded computational domain at a finite distance to reduce the requirement of computational resources. To manage this truncation, artificial boundaries are introduced, among which the Scaled Boundary Perfectly Matched Layer (SBPML) is regarded as a reliable strategy. In this paper, we implement the SBPML element into the commercial software ABAQUS using the User-Defined Elements (UEL) subroutine. The key equations of the SBPML, the procedures of meshing for the SBPML domain, and the implementation workflow of the subroutine are given in details. Four benchmark examples of wave propagation problems in unbounded domains are presented to demonstrate the accuracy and effectiveness of the proposed method. Furthermore, the application of the UEL in nonlinear seismic soil-structure interaction analysis is demonstrated by evaluating the seismic response of a five-layer alluvial basin in a homogeneous half space and an aboveground-underground integrated structure-multilayer soil system under obliquely incident earthquake waves. Using the proposed UEL, all wave propagation analyses can be directly implemented in ABAQUS with a seamless workflow. To facilitate the use of the proposed approach, the codes of the UEL are published in an open-source format.

This paper aims to investigate the wave-induced evolution of small-strain stiffness and its effects on seismic wave propagation. To this end, an advanced numerical framework based on the dynamic porous media theory was developed, in which the Iwan multi-surface constitutive model was adopted to model the soil behavior during cyclic loading. Moreover, the numerical framework integrates key parameters such as ocean wave characteristics and depth-dependence seabed conditions to model the intricate interactions between waves and the seabed. Following model verification via analytical solutions and previous experimental data, comprehensive parameter studies are conducted, from which the effects of different wave conditions and seabed properties on the dynamic response of the seabed were obtained, revealing the wave-induced small- strain stiffness spatial and temporal variation. Subsequently, simulations of geophysical monitoring instants are conducted, assessing the impact of evolving small-strain stiffness on seismic wave propagation. The findings highlight the implications of stiffness changes on seismic wave propagation characteristics. The study provides valuable insights into the challenges and opportunities associated with interpreting geophysical data in dynamic submarine environments, offering implications for subsurface characterization and monitoring applications.

The damage effects of the earthquake on tunnels crossing faults are categorized into two types: inertial forces generated by ground motions and permanent stratigraphic deformations caused by fault dislocations. A seismic dynamic analysis method of tunnel considering coseismic dislocation is proposed by introducing the numerical simulation of seismic wave propagation into the soil-structure dynamic analysis research field. First, seismic waves are simulated according to the finite-difference method. The stress, displacement, and velocity of nodes on the truncated boundary of the soil-structure model can be calculated according to the seismic wave propagation simulation method. Then, the seismic waves and dynamic dislocation load are simulated in the finite element model by the viscous-spring boundary. Based on the free-field model, the reliability of the presented method is validated in simulating coseismic deformation and seismic waves. In the case of the 2022 MS 6.9 Menyuan earthquake and the Daliang tunnel, which was severely damaged by this earthquake, the deformation of the tunnel simulated based on the presented method is consistent with the previous method. The proposed method can offer guidance for the seismic fortification of tunnel engineering.

To design a suitable dynamic wave propagation model to portray the wave dispersion law in fluid-containing granular materials, we consider the effects of the particle geometry and frequency on the dynamic tortuosity and construct a branching function to solve the degradation of the potential energy function of granular materials. Then, the stress-strain relationship between fluid and solid materials is resculpted using the viscoelastic constitutive relationship containing the relaxation state, and a new dynamic wave propagation model, SRVE (wave propagation with shape and stress relaxation related viscoelastic), which is capable of encompassing the integrated dissipation mechanism of frictional, viscoelastic, and relaxation dissipation, is obtained. Finally, the reliability of the SRVE model was verified by carrying out wave velocity tests on calcareous sand granular materials in the South China Sea. The results show that the main dissipation mechanisms of fluid-containing granular materials are assumed to be frictional dissipation, viscoelastic dissipation and relaxation dissipation in order of increasing frequency values, with different dissipation mechanisms assuming the main roles at different eigenfrequencies. The frictional dissipation eigenfrequency, viscoelastic dissipation eigenfrequency and relaxation dissipation eigenfrequency of the P-wave of the calcareous sand are 0.5 Hz, 30 Hz and 100 Hz, respectively, whereas those of the S-wave are 0.5 Hz, 12 Hz and 80 Hz, respectively.

Reservoir geologic fluid-bearing granular materials are characterized by multiscale nonuniformity and coupled multiphysical mechanisms, for which conventional poroelastic theory cannot accurately portray wave dispersion and attenuation characteristics. To design a suitable dielectric wave propagation model to characterize the dispersion and attenuation laws of dynamic waves in geologic reservoirs, first, the branching functions of frequency-dependent dynamic permeability and dynamic tortuosity are derived by considering the effects of the geometry and fractal structure of fluid-bearing granular materials on the high-frequency properties of permeability and tortuosity. Second, the stress-strain relationship of the fluid-particle system is redrawn by the viscoelastic-plastic constitutive relation, and the dynamic wave propagation model of fluid-containing granular materials at a unified frequency is constructed by an integrated dissipation mechanism including frictional dissipation, internal dissipation, and plastic energy dissipation-wave propagation model based on viscoelasticplastic constitutive relation and dynamic permeability (WVPDP model). Finally, the reliability of the WVPDP model is verified by carrying out wave velocity tests on saturated dolomite and sandstone, and the effects of different parameters on the wave velocity dispersion amplitude and attenuation peak are analysed. The results show that the WVPDP model can accurately characterize the dispersion and attenuation of dynamic waves in granular media under uniform high and low frequencies and can invoke different dissipation mechanisms at different excitation frequency intervals, which is shown by the fact that internal dissipation and the plastic mechanism play the main role in the low-frequency interval, and frictional dissipation gradually replaces internal dissipation and plastic dissipation to become the main dissipation mechanism with increasing excitation frequency. Parameters such as fluid viscosity, reference angular frequency and reference quality can have different effects on the dispersion amplitude and transition band range of the fast P-wave and S-wave, the two mechanical response mechanisms in the medium of fluid-containing granular materials.

Geophysics and Geotechnical Engineering commonly use 1-D wave propagation analysis, simplifying complex scenarios by assuming flat and homogeneous soil layers, vertical seismic wave propagation and negligible pore water pressure effects (total stress analysis). These assumptions are commonly used in practice, providing the basis for applications like analysing site responses to earthquakes and characterizing soil properties through inversion processes. These processes involve various in situ tests to estimate the subsurface soil's material profile, providing insights into its behaviour during seismic events. This study seeks to address the limitations inherent to 1-D analyses by using 3-D physics-based simulations to replicate in situ tests performed in the Argostoli basin, Greece. Active and passive source surveys are simulated, and their results are used to determine material properties at specific locations, using standard geophysical methods. Our findings underscore the potential of 3-D simulations to explore different scenarios, considering different survey configurations, source types and array sets.

In the context of soil-structure interaction analysis, the deconvolution process for computing effective earthquake loads within rock profiles holds significant importance. This study explores the implications of this process on structures founded on rock with linear response and high shear wave velocity. The structures are subjected to both real ground motions and intensifying artificial accelerations (IAA). By employing detailed nonlinear finite element simulations on a concrete dam with a massed foundation, two distinct scenarios are explored. In the first scenario, all selected motions are deconvolved to the specified depth, and the resultant equivalent nodal forces are used. The second scenario involves treating the input excitations as outcrop motions, with corresponding effective earthquake loads directly applied to the depth. The outcomes underscore that neglecting the deconvolution process for real ground motions leads to an overestimation of structural responses. The magnitude of this discrepancy remains uncertain and is influenced by ground motion aleatory variability and damping ratio. Concurrently, this paper introduces a practical framework that circumvents the deconvolution process for IAAs, while upholding an acceptable level of accuracy. The deconvolved IAAs offer simplicity of use and expedite the risk assessment process for complex geostructures.

Rapid changes in geotechnical and geological ground conditions lead to significant ground motion variability. This condition mainly occurs at the so-called basin edges, where there is an abrupt transition between soft highly compressible soils and stiffer materials. This problem becomes more relevant in areas where ground subsidence drastically changes the dynamic response of high plasticity clay deposits, such as those found in Mexico City, due to fundamental site period evolution with time. This paper presents site response analyses at an abrupt transition area in the southeast Mexico City region, along the edges of the Xochimilco-Chalco lakes. Considerable damage associated with three-dimensional wave propagation effects was observed in this zone during the September 2017 Puebla-Mexico earthquake. A series of three-dimensional finite difference numerical models of the basin edge were developed to evaluate ground motion variability, considering topographic effects and soil non-linearities. Good agreement between the computed response and the observed damage during the 2017 Puebla-Mexico earthquake reconnaissance was found. In addition, several normal and subduction events with a return period of 250 years were considered to evaluate the effect that frequency content, and strong ground motion duration have on the soil response variability. From the results gathered here, it was established the relevance of accounting for three-dimensional wave propagation fields to assess site effects at basin-edge zones properly and to be able to implement proper risk mitigation measurements at these zones.

Vibrations due to construction activities and the resultant oscillation and potential damage of adjacent structures is an important issue in soil dynamics. To prevent damage, the intensity of building vibration on the subsoil and also on the building must be predicted. In most application cases, empirical equations are used to estimate the intensity of vibration (in terms of peak vibration velocity). However, these equations normally do not take site-specific soil conditions into account, but consider an energy term dependent on the construction machine and the distance of the operating machine to the considered building. In the paper, building vibrations due to vibratory rollers are considered. First, empirical approaches from literature are described and compared. Then, a numerical simulation model is presented, which allows the determination of peak vibration velocities due to vibratory roller operation of the soil in the free field as well as of a footing. A parametric study is conducted which shows the effects of subsoil conditions (i.e. soil layering and soil stiffnesses) and footing dimensions on the vibration intensities at varying distances to the vibratory roller. From a comparison of free field and foundation peak velocities, also transmission coefficients from soil to footing are determined.