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In this study, the sediment transport two-phase flow model named SedFOAM is expanded to include soil cohesion, creating a new model named SedCohFOAM within OpenFOAM. The local scouring flume experiment involving a pile on silty seabed and sandy seabed is conducted in a curved flume. Due to the influence of cohesion, the scouring depth at different locations on sandy seabed is 15%–18% greater than that on silty seabed. Observations from this experiment informed the analysis of force balance, wherein the agglomerated silt particles are modeled as large singular entities and the cohesive force is treated as a downward influence that keeps the aggregated particles stationary. Meanwhile, the experimental outcomes are utilized to validate the accuracy of the SedCohFOAM model. The numerical findings demonstrated that SedCohFOAM can simulate the flow field distribution around the pile, variations in seabed shear stress, and alterations in seabed surface morphology. Compared with the SedFOAM model, the SedCohFOAM model has a significantly reduced simulation error in simulating scour on silty seabed. When comparing the cross-sectional profiles of the scour holes derived from the flume experiments with those simulated by SedCohFOAM, it was observed that the ultimate-equilibrium scour depth predicted by the model is consistently lower, but the scour radius in the numerical simulations is larger. The deviation from the experimental results is nearly within 8%, while when the flow velocity is high, the simulation error of the simulated scouring depth behind the pile and the scouring radius in front of pile is amplified. [ABSTRACT FROM AUTHOR]

Skirt–pile foundations have gained widespread attention in the field of offshore engineering due to their ease of installation and high bearing capacity. In this study, the ultimate bearing capacity, pile bending moment distribution and development, cumulative deformation characteristics, and cyclic stiffness development of skirt–pile foundations were investigated using physical model tests. The experimental results indicate that the ultimate bearing capacity and deformation resistance of the foundation can effectively be improved by increasing the skirt diameter. The cumulative deformation of the skirt–piles exhibited rapid development during the initial stages of cyclic loading, eventually stabilizing. Under long-term cyclic loading, the existence of the skirt can share the bending moment, which then affects the internal force distribution of the pile foundation along the axis. The pile foundation's cyclic stiffness reduces as the loading cycles increase and increases as the skirt diameter and length grow. Meanwhile, the horizontal cyclic stiffness decreases as the number of cycles increases, stabilizing after 3000 cycles. This study can not only deepen the understanding of the deformation laws of skirt–pile foundations in clay soil but also offers some references for the design of offshore pile foundations. [ABSTRACT FROM AUTHOR]

In this paper, a two-dimensional numerical model for wave-seabed-pipeline interaction is developed to examine the wave-induced uplift force onto pipelines buried in sloping seabeds. The Reynolds-averaged Navier stokes equation and the poro-elastic equation are used to simulate the wave motion and seabed response, respectively. Meanwhile, the pipeline is considered to be elastic. Firstly, three laboratory experiments are taken to verify the effectiveness of the numerical model. Then, the effects of pipeline characteristics, soil properties and wave parameters on the nonlinear wave-induced uplift force onto a pipeline buried in a sloping seabed are analyzed. Finally, an empirical formula for predicting the nonlinear wave-induced uplift force onto buried pipelines under different slope angles is proposed. It can be found that the slope angle can greatly affect the nonlinear wave-caused pore pressure response, as well as the uplift force onto the pipeline. Moreover, the simple method for predicting the uplift force proposed in this paper can facilitate engineering applications. [ABSTRACT FROM AUTHOR]

In order to investigate the cumulative deformation of the pile group in saturated clay under horizontal cyclic loading, a series of 1g model tests were conducted using the self-made loading equipment in this paper. Firstly, the loading equipment and testing procedure are introduced. Then, the cumulative deformation of the pile group, the dynamic response of the soil, and the bending moment of the pile shaft under horizontal cyclic loading are studied. Finally, the horizontal cyclic stiffness of the pile group is analyzed based on the experimental results. It can be found that the cumulative displacement, the rotation angle of the bearing platform, the pile shaft bending moment, and the pore water pressure can attain 90% of the peak values within the first 1000 cycles, and the growth rate slows down in subsequent loading cycles. Moreover, the bending moment of each pile increases with the burial depth and gradually decreases after the peak values. Notably, the horizontal cyclic stiffness of the pile group grows with the cycle loading times and decreases with the loading amplitude. [ABSTRACT FROM AUTHOR]

Based on a Wharf project in Chongqing, this paper carries out experimental research and nonlinear finite element analysis on the impact resistance of steel casing rock socketed pile of inland river frame Wharf under horizontal impact load. The results show that the impact force and its growth rate, the bending moment of concrete pile core, and the maximum lateral displacement of pile top increase significantly with the increase of impact energy, and the linear increase of the maximum displacement of pile top is better. Under the same impact energy, with the increase of impact mass, the maximum impact force decreases, the maximum bending moment of concrete pile core and its vibration center value (platform value) increase, and the maximum displacement of pile top and its vibration center value (platform value) increase. Based on the impact mass m threshold, the criterion of different dynamic response forms of pile body is proposed. The impact mass threshold corresponds to the development of plastic hinge at the root of pile body. Through the parametric analysis method, it is obtained that the impact mass, impact velocity, and the maximum displacement of pile top meet the parabolic spherical relationship. [ABSTRACT FROM AUTHOR]

To investigate the wave- and current-induced seabed response near a fully buried subsea pipeline, a two-dimensional coupled model for fluid-seabed-pipeline interaction (FSPI-2D) is developed within the framework of COMSOL multiphysics. Different from previous studies, both the wave-current interaction and the nonlinear pipeline-soil contacts are considered in the present model. In this paper, Biot's consolidation mode is used to govern the fluid-induced seabed response, and combined Reynolds averaged Navier–Stokes (RANS) equation with the k-ε turbulence model is employed to simulate the fluid propagation. Meanwhile, the pipeline is treated as a linear elasticity. Firstly, the effectiveness of the new model is verified by laboratory experiments from previous reports. Then, the numerical model is employed to examine the effects of nonlinear pipeline-seabed contacts and fluid characteristics on the seabed response around the structure. Finally, the momentary liquefaction near the fully buried pipeline is studied based on the 2D coupled model. [ABSTRACT FROM AUTHOR]

To explore the pile-soil interaction response in saturated sand under long-term horizontal cyclic loading, a series of indoor 1 g model tests were carried out with self-made loading equipment. In this paper, the self-made loading system and test program are introduced firstly. Then, the long-term horizontal cyclic loading-induced pile top cumulative displacement, the rotation angle, the mono-pile horizontal cyclic stiffness, the cyclic p-y curve, the pore water pressure, the soil settlement, and cracks around mono-pile are fully studied. Based on the experimental results, the pile-soil interaction response shows a two-stage characteristic with the change in cycle (N), and the short-term effects of horizontal cyclic loading are greater than the long-term effects. In the first 1000 cycles, the cumulative displacement of pile top, the rotation angle of mono-pile, and the pore water pressure could reach more than 90% of the final value. In addition, the cyclic p-y curve obtained by the test is generally smaller than the p-y curve calculated from the API specification, and the soil near the mono-pile will settle with annular cracks under the cyclic loading. [ABSTRACT FROM AUTHOR]

To obtain a better understanding of the oscillatory soil liquefaction around an offshore pipeline, a three-dimensional integrated model for the wave–seabed–pipeline interaction (WSPI) is proposed by combining the Reynolds-Averaged Navier–Stokes equations for flow simulations and the dynamic Biot’s equation (“ u - p ” approximation) for the poro-elastic seabed model. Compared with previous investigations, the wave–current interaction is included in the present WSPI system. At a given time step, the wave pressure extracted from the flow model is applied on the seabed surface to determine the corresponding oscillatory seabed response around an offshore pipeline. The integrated numerical model is first validated using previous laboratory experiments. Then, a parametric study is conducted to examine the effects of flow obliquity and pipeline burial depth on the soil response around an offshore pipeline. Numerical results indicate that the soil under the pipeline is more susceptible to liquefaction at a reduced flow obliquity and pipeline burial depth. Moreover, the liquefaction depth in the case where the wave travels along the current can increase by 10%–30% compared to that in the case where the wave travels against the current, when the magnitude of the current velocity is 1 m/s. [ABSTRACT FROM AUTHOR]

• A novel 3D numerical model for residual seabed response has been developed by redefining the source term of the governing equation. • The wave-current interactions are considered while studying residual soil response near a single pile. • Both the oscillatory pore pressure and the residual pore pressure are considered while determining soil liquefaction potential. The evaluation of seafloor stability is of vital importance for engineers involved in the protection of marine foundations. Hence, it has attracted considerable attention in the field of offshore geotechnical engineering. In this investigation, a novel three-dimensional (3D) numerical model of fluid–seabed-structure interactions (FSSI) is proposed within the framework of OpenFOAM to explore the residual soil dynamic response around a single pile. Different from previous studies, three new features are added in the present model. (i) The wave–current interactions are taken into consideration, (ii) the source term of pore pressure generations is redefined, and (iii) both the oscillatory pore pressure and residual pore pressure are considered while judging the soil liquefaction potential. After verified by previous laboratory experiments available in literature, the novel model is applied to investigate the residual soil response around the single pile induced by natural loadings. The numerical results confirm that the novel 3D model can provide sufficiently accurate predictions of fluid–seabed-structure interactions. Moreover, wave/current characteristics, soil properties, and pile diameter can significantly affect the fluid-induced residual pore pressures along the vicinity of the single pile. [ABSTRACT FROM AUTHOR]

In this paper, the results of a series of experiments on wave-induced pore-water pressures around a mono-pile are presented. Unlike the previous study, in which the mono-pile was fully buried, the mono-pile in this study was installed at 0.6 m below the seabed surface. In this study, we focus on the pore-water pressures around the mono-pile and beneath the pile. The experimental results lead to the following conclusions: (1) the seabed response is more pronounced near the surface (in the region above 30 cm deep), and the rate of pore pressure attenuation gradually slows down. For the region below 0.3 m, the response is much smaller; (2) in general, along the surface of the pile, pore pressures increase as the wave height and wave period increase; (3) the spatial distribution of pore pressure near the pile will vary with different wave periods, while the wave height only has a significant effect on the amplitude; and (4) At z = −0.15 m, the pore pressure in front of the pile is the largest, while at the point 0.1 m below the bottom of the pile, the largest pore pressure occurs behind the pile. [ABSTRACT FROM AUTHOR]

Background: Irrigation is considered to be a critical part of root canal treatment. However, little is known about the effect of needle movement on the irrigation process. Therefore, this study aimed to investigate the influence of the syringe and needle movement on root canal irrigation using a three-dimensional computational fluid dynamics (CFD) numerical model.Methods: The CFD codes Flow-3D was adopted to simulate the root canal irrigation process with the syringe and needle moving up and down in motions at different amplitudes and frequencies. One stationary needle was adopted to allow comparison with the needles in up-and-down motions. Six cases where the needles were moving up and down with different amplitudes and frequencies were used to investigate the relationships between the motion of needle and irrigation efficacy.Results: The stationary needle gained relatively higher flow velocity and apical pressure all through the irrigation process, while the needles in constant up-and-down motions exhibited lower mean flow velocity and apical pressure. The larger the amplitude, the less mean flow velocity and apical pressure were developed. In addition, the needles moving with different frequencies were similar in the terms of irrigant replacement and apical pressure.Conclusions: To avoid periapical extrusion accidents while obtaining adequate irrigant replacement, the needle should be moving up and down with a moderate amplitude during manual root canal irrigation; and the motion frequency was not highly relevant in terms of the irrigation efficiency. [ABSTRACT FROM AUTHOR]

• An integrated FEM model of wave-seabed interaction is used to investigate the effects of wave-current action on the slope instability for the foundation trench of immersed tunnel. • The wave and current induced seepage pressure in the seabed is determined by Darcy's law and considered as external load. • The consolidation status of foundation trench after excavation is obtained and set as an initial condition. • The factor of stability (FOS) for the slope depends on the relative distance between the wave crest and slope. • The minimum of FOS corresponding to the most dangerous situation is regarded as the stability index for the slope in the whole process of dynamic wave-current loading. The determination of stability for the submarine artificial slope is important in the construction of offshore structures such as immersed tunnels and embedded pipelines. Aimed at this issue, a two-dimensional (2D) integrated model is proposed to investigate the slope stability of the foundation trench for the immersed tunnel under the combined wave and current loading, as in the real marine environment. The Reynolds-Averaged Navier-Stokes (RANS) equations are solved to simulate the wave field, meanwhile the current is realized by setting boundary inlet and outlet velocity at both sides. The interface between water and air is tracked by conservative Level Set Method (LSM). The wave-current induced pore pressure in seabed is calculated by Darcy's law, and the shear strength reduction method is adopted to judge the damage of the elastic-plastic seabed slope which is described through Mohr-Coulomb constitutive model. The wave-current model is validated through comparing with experimental data and analytical solution. The consolidation status of foundation trench after excavation is obtained and set as the initial condition for analysis. The factor of stability (FOS) for the slope is demonstrated to depend on the relative distance between wave crest and slope. The minimum of FOS corresponding to the most dangerous situation is regarded as the stability index for the slope with specific slope ratio in the whole process of dynamic wave-current loading. Through the parametric analysis based on this new evaluation method, the effects of soil strength parameters, slope ratio and current direction on the slope stability are discussed in detail. [ABSTRACT FROM AUTHOR]

• Experimental study for random wave-induced soil response around a mono-pile. • The influence of wave height on the maximum pore-water pressure is significant in the region near seabed surface (| z | < 0.3 m). • Significant difference of pore pressure distribution around a mono-pile between regular wave and irregular wave loading. In this study, a series of physical model tests were carried out in a wave flume to study the pore pressures around a mono-pile under irregular waves. The mono-pile was installed to the position of 0.6 m below the seabed surface. The main purpose of this study is to analyze the distribution of pore-water pressure around and beneath the mono-pile under irregular waves. Five different wave spectra were used in the tests. The experimental results conclude that: (1) the pore-water pressure around the pile increases as the increase of significant wave height and period; (2) the maximum pore-water pressure decreases as the increase of seabed depth (z), this trend is significant near the seabed surface (z ≥ −0.3 m), and the influence is not obvious for the region below 0.3 m; (3) at the depth of 0.15 m below the seabed surface (z = −0.15 m), the maximum pore pressure occurs in front of the pile, and at the depth of 0.1 m below the bottom of the pile (z = −0.7 m), the maximum pore-water pressure occurs behind it; (4) the irregular wave-induced seabed response is larger than that of the representative regular wave; and (5) the irregular waves with Pierson–Moscowitz (P − M) spectrum introduce the most significant seabed response among various wave spectra. [ABSTRACT FROM AUTHOR]