Numerical study for wave-induced oscillatory pore pressures and liquefaction around impermeable slope breakwater heads

Liao, Chencong; Tong, Dagui; Jeng, Dong‐Sheng; Zhao, Hongyi

doi:10.1016/j.oceaneng.2018.03.058

Cited by 44 publications

(12 citation statements)

References 46 publications

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“…The evaluation of the wave-induced soil response in marine sediments is particularly important for the design of foundations of offshore installations such as wind turbine foundations (Cuéllar, 2012;Lin et al, 2017), platforms (Bea et al, 1983;Zhang et al, 2017), pipelines (de Groot and Meijers, 1992; Zhou et al, 2015) and breakwaters (Oumeraci, 1994;Zhang and Ge, 1996;de Groot et al, 2006;Liao et al, 2018aLiao et al, , 2018b. Therefore, it is necessary to have a better understanding of the wave-induced pore-pressure in marine sediments.…”

Section: Introductionmentioning

confidence: 99%

Combined wave-current induced excess pore-pressure in a sandy seabed: Flume observations and comparisons with theoretical models

Jeng

et al. 2019

Coastal Engineering

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Waves are coexisting with currents in coastal zones; nevertheless, previous experimental studies for excess pore-pressure responses in a porous seabed were predominantly limited to the wave-only condition. In this study, the combined wave-current induced excess porepressures in a sandy seabed were experimentally simulated with a specially-designed flume, which can concurrently generate periodic waves and a following/opposing co-directional current. The effect of a current on the wave profile is firstly examined. The wave steepness is decreased by a following current, but enhanced by an opposing current. Flume observations indicate that, under combined wave-current loading, the wave-induced pore-pressure is increased for the following-current case, but reduced for the opposing-current case. Such wave-current combination effect becomes more significant for shorter wave periods. The variation trend of the excess pore-pressure distribution in the present flume observations is consistent with that of the existing analytical solutions. Nevertheless, due to the existence of wave and/or current boundary layer and non-lineartiy of wave-current interactions as indicated by the flume observations, certain deviations exist between the flume results for excess pore-pressure and the analytical solutions, which can not be ignored especially for the opposing-current case. The effects of the boundary layer on the combined wave-current induced pore-pressures in the seabed are further highlighted by supplementary numerical simulations. A favorable prediction by the analytical solution would be expected for following-current cases and smaller pore-pressure amplitudes would be obtained for opposing-current cases.

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Section: Introductionmentioning

confidence: 99%

Combined wave-current induced excess pore-pressure in a sandy seabed: Flume observations and comparisons with theoretical models

Jeng

et al. 2019

Coastal Engineering

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“…An integrated numerical model proposed by Liao [23] is set up to calculate the wave-induced seabed response around a mat foundation numerically. This numerical model has been employed and verified repeatedly in previous researches [3,[23][24][25], and it consists of two sub-models: The flow sub-model and the seabed sub-model. For the flow sub-model, the finite volume method (FVM) is employed to solve the Reynolds-averaged Navier-Stokes (RANS) equation in FLOW3D ® .…”

Section: Numerical Verificationmentioning

confidence: 99%

Experimental Study on the Distribution of Wave-Induced Excess Pore Pressure in a Sandy Seabed around a Mat Foundation

Yuan

Liao

Zhou

2019

JMSE

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Mat foundations are widely used in jack-up offshore platforms to support and transfer loads. Regarding mat foundations working on the seabed, the excess wave-induced pore pressure is critical to seabed stability, which may finally cause structural failure. Therefore, it is important to investigate the distribution of the excess pore pressure in the seabed around the mat foundation. In this study, experiments were performed to study the excess pore pressure distribution around a mat foundation in scale considering the true load state by recording wave profiles and pore pressures inside a sandy seabed. To guarantee the reliability of experiments, a numerical study was conducted and compared with the experimental results. Experimental results indicate that with the existence of the mat foundation, the excess pore pressure is higher at the region, the range of which is the width of the model mat (Wm) before the structure. The maximum pore pressure appears at 0.55 Wm in front of the center of the mat foundation. In addition, the current significantly increases the range of high pore pressure area and the amplitude of the excess pore pressure. As the mat orientation changes, the position of the maximum pore pressure changes from the front to the edge of the mat.

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“…Tidal-scale processes in fresh-salt water mixing are well understood through in situ observations, laboratory experiments and numerical simulations, however, relative little is know about the hydrodynamic processes on intra-tidal time scales. These small scale flow structures, such as turbulence and instabilities, are the dominant mechanism for the transition from organized flow to turbulence, which is critical to the understanding of the hydrodynamics and mass transport in estuarine areas [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Kelvin-Helmholtz Billows Induced by Shear Instability along the North Passage of the Yangtze River Estuary, China

Shi

Tong

Zheng

et al. 2019

JMSE

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Kelvin-Helmholtz (K-H) instability plays a significant role in mixing. To investigate the existence of K-H instability along the North Passage of the Yangtze River Estuary, the non-hydrostatic model NHWAVE is utilized to simulate the fresh-salt water mixing process along the North Passage of the Yangtze River Estuary. Using high horizontal resolution, the structure of K-H billows have been successfully captured within the Lower Reach of the North Passage. The K-H instability occurs between the max flood and high-water slack. The duration and length scale of the K-H billows highly depends on the local interaction between fresh-water discharge and tide. The horizontal length scale of the instability is about 60 m, similar to the observations in other estuaries. In the vertical direction, the K-H billows exist within the pycnocline with length scale ranging from 6 to 7 m. The timescale of the billows is approximate 6 min. By analyzing the changes of potential energy during the mixing process, results show that the existence of K-H instability induces intense vertical mixing, which can greatly increase mixing efficiency in the North Passage of the Yangtze River Estuary.Miles [10] and Howard [11] showed that a necessary condition for K-H instability in a parallel, stratified, inviscid flow, is that the gradient Richardson number (Ri = N 2 /S 2 , where N = −(g/ρ)(∂ρ/∂z) is the Brunt-Väisälä frequency, S = du/dz is the velocity shear, g is the gravity acceleration, ρ is density and u is a representative flow speed) is less than 0.25 somewhere in the flow. However, it has been demonstrated this criterion is not sufficient [12], because it is possible to have a stable shear layer when Ri < 0.25 at the pycnocline. Fringer and Street [13] found the interfacial wave can be stable with Ri < 0.25, but unstable perturbations occurred when Ri < 0.13. Barad and Fringer [14] used an adaptive numerical method to evaluate the critical Ri for instability, and the result showed a similar value of Ri < 0.1 is required for instability. Based on laboratory experiments, Fructus et al. [15] proposed a new criterion for instability, which is L x /λ > 0.86, where L x is the length of the region with Ri < 0.25 and λ is the wave width. Another alternative criterion for instability is based on the linear stability analysis with the Taylor-Goldstein equation. Troy and Koseff [16] used the equation to derive the criterion for instability, which requiresσ i T w > 5, where T w is the time the fluid spends in region with Ri < 0.25 andσ i is the averaged growth rate of the instabilities in the region.

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Numerical study for wave-induced oscillatory pore pressures and liquefaction around impermeable slope breakwater heads

Cited by 44 publications

References 46 publications

Combined wave-current induced excess pore-pressure in a sandy seabed: Flume observations and comparisons with theoretical models

Combined wave-current induced excess pore-pressure in a sandy seabed: Flume observations and comparisons with theoretical models

Experimental Study on the Distribution of Wave-Induced Excess Pore Pressure in a Sandy Seabed around a Mat Foundation

Kelvin-Helmholtz Billows Induced by Shear Instability along the North Passage of the Yangtze River Estuary, China

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