Experimental dynamic sediment behavior under storm waves with a 50 year recurrence interval in the Yellow River Delta

The dynamic response of marine sediment from the Yellow River under extreme sea conditions is attracting increasing academic and engineering attention because of the high occurrence frequency of geologic hazards. To simulate the dynamic response process of sediment samples under waves with a 50 year recurrence interval, we collected undisturbed sediment samples from six sites on the intertidal flats of the Yellow River Delta and performed dynamic triaxial experiments to analyze the pore-water pressure and liquefaction process. The empirical patterns of pore-water pressure generation and ranges of sediment parameters were determined, and the factors affecting sediment liquefaction were discussed. Under the cyclic loading of waves with a 50 year recurrence interval, the pore pressure response of sediments at a depth of 4 m could be generalized into three stages: rapid growth, slow growth, and stable maintenance. Moreover, the build-up of pore-water pressure was effectively represented by a logarithmic growth model. The liquefaction characteristics of sediment in the Yellow River Delta were more related to its plasticity index, mean particle size, and clay, silt, and sand contents, as well as the sedimentary history. These factors should be considered in the development of disaster assessment models in coastal environments of the Yellow River Delta.


Introduction
The world's deltas, as the interface between the land and the ocean, nourish half a billion people worldwide and play a key role in global ecosystem by providing fertile soil and abundant natural resources (Syvitski 2008). As natural recorders of depositional conditions, deltas are sensitive to both human activity (e.g., damming, irrigation, water, oil, and gas mining) and global environmental changes (e.g., warming, aridification, acidification) (Milliman 1997;Bianchi and Allison 2009). Accordingly, deltaic depositions formed by sediment discharged from rivers have complex sedimentary structures and engineering characteristics that require careful consideration in human engineering projects (Amos et al. 1997). It is estimated that 85% of global river deltas have been subjected to the risk of erosion during the first decade of the 21st century, which has increasingly affected the safety of engineering facilities and people living on the deltas (Syvitski et al. 2009). Consequently, the manner in which the properties of deltaic sediment respond to alterations in the global environment is a topic of worldwide concern.
The Yellow River Delta, where Shengli Oil field is located, is a typical example of interactions between human activities and coastal environments. The sediment load delivered by the Yellow River to the sea decreased stepwise during the period of 1950-2005 primarily due to human activities, such as dam construction, water consumption, and soil conservation practices (Wang et al. 2007). This resulted in a deltaic deposition with complex engineering and geological characteristics, changing at different spatial and temporal scales under the influence of local sedimentary environment (Fan et al. 2006). The storm wave is one of the most frequently occurring and damaging natural hazard phenomena in the Yellow River Delta and has a significant impact on the sediment dynamic properties (Prior et al. 1989;Wang et al. 2017).
Studies of the sediment dynamics in the Yellow River Delta began in the mid-1980s when marine scientists in China, the United States, and Canada jointly conducted the project "Sedimentary Dynamics of the Huanghe (Yellow River) Delta and Neighboring Gulf of Bohai" . The project first determined the number of unstable geologic hazards on the seafloor of the Yellow River Estuary, including collapses and pits, silty flows, and submarine landslides ), which were considered to be closely related to extreme sea conditions (Prior et al. 1989). More recently, theoretical studies have been conducted based on a series of field investigations and drill-hole data by Chinese marine geologists (e.g., Li et al. 2000;Jia et al. 2011aJia et al. , 2011bWang et al. 2018). For instance, Sun et al. (2008) found that the residual liquefaction depth could reach 4.2 m, as induced by extreme sea conditions, such as storms, which could be considered as the main factor driving the large distribution of the disturbed sediment layer. Meanwhile, Liu et al. (2013a) found that strong wave action is crucial to sediment consolidation in the primary period and plays a decisive role in the development of a stiff stratum. Finally, Wang and Liu (2016) demonstrated that wave-induced scour-erosion, seepage instability, and shear slide are all possible instability modes under the 1 year storm waves, and scour-erosion is predominant for the 50 year storm waves.
A number of studies have analyzed sediment dynamics in response to waves under extreme sea conditions in offshore or coastal environments using numerical methods (Jeng and Hsu 1996;Ye et al. 2014;Liao et al. 2015;Yang and Ye 2017). However, numerical simulation results are often restricted by the complex interaction mechanism between wave cyclic loadings and sediment particles. To address this limitation, laboratory experiments, including shaking table test, resonant column test, dynamic triaxial test, and flume experiments, are widely used to study sediment processes under waves (Roulund et al. 2005;Ueng et al. 2006;Liu et al. 2017). Dynamic triaxial experiments are used most widely to study sediment dynamic characteristics, because they enable good control over the test conditions and have good repeatability (Seed and Idriss 1970;Saglam and Bakir 2014;Chen et al. 2016). Moreover, pore-water pressure variations and sediment liquefaction failure criteria of silty sediment under waves are more readily obtained via dynamic triaxial experiments to allow comparisons with numerical calculations (Prakash and Sandoval 1992;Guo and Prakash 1999;Chien et al. 2002). Although previous studies have focused on the sediment dynamic behavior in the Yellow River Delta and the relationship between the pore-water pressure development and particle content of silty sediment (Luan et al. 2008;Zeng et al. 2008;Xu et al. 2012), the temporal matching between the sediment characteristics and sedimentary periods of the Yellow River Delta were not fully taken into account, thus being a source of considerable error.
Therefore, in this study, we (i) performed dynamic triaxial experiments to simulate the interaction process between wave loading under extreme sea conditions with a 50 year recurrence interval using sediment samples from the Yellow River Delta and (ii) created a model of pore pressure. The pore-water pressure accumulation and sediment liquefaction processes were observed, and the influencing factors of the pore-water pressure accumulation model and sediment liquefaction properties were discussed.

Study site
The study area was located in the Yellow River Delta (Fig. 1), which is formed by the rapid deposition of a large amount of sediment carried by the Yellow River. It has been estimated that extremely high sediment loads (>1000 million tonnes per year, Mt/a) from the Chinese Loess Plateau have been transported by the Yellow River and deposited near the river mouth due to the low tidal range and slow rate of sea level rise (e.g., Ren and Shi 1986;Wang et al. 1992;Wang and Liang 2000).
The large annual sediment load combined with the dramatic changes over the course of the Yellow River has resulted in a complex and episodic deltaic history (Qin and Li 1983). Owing to natural and anthropogenic factors, the Yellow River has frequently changed its course and breached since it began to empty into the Bohai Sea in 1855 (Saito et al. 2000). There are eight lobe bodies in the modern Yellow River Delta (i.e., since 1855; Fig. 1). Seven of the lobes formed before 1976, when the Yellow River emptied into the Bohai Sea, representing a total run time span of 112 years, and the average active period of each lobe was 16 years, considerately shorter than the active period of 115∼175 years for the lobes of the

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Mississippi Delta (Wells and Coleman 1987). The cutting off of sediment sources to these abandoned lobes poses a serious threat and great economic loss on the construction of onshore and offshore oilfields and comprehensive management and exploitation of the Yellow River Delta (Bi et al. 2014;Zhou et al. 2015). The modern Yellow River Delta is composed of 11 sub-lobes deposited in different sedimentary periods (Chu et al. 2006), with sediment distributions showing different characteristics under different marine hydrodynamic conditions (Jia et al. 2011a). In this study, samples (i.e., at least five cores at each site) were collected from undisturbed silty sediment deposits from six of these sub-lobes. Figure 1 shows the distribution of the sampling sites (S1, S2, S3, S4, S5, and S6), and Fig. 2 presents photographs of the six sampling sites. Three sites (S3, S4, and S6) are adjacent to the impermeable groins that were constructed by the Shengli Oil Company to protect the safety of engineering activities in the Yellow River Delta from severe erosion (Figs. 2c, 2d, and 2f).

Sediment analysis
We conducted a number of conventional physical and mechanical property tests on the core samples collected from the six study sites. The surface sediment samples (50 cm in length and 75 cm in diameter) were collected with a PVC sampling tube for indoor tests following the standard for soil test method (GBT 50123-1999). The natural density and water content were tested using the cutting ring and drying methods. The undrained shear strength and penetration strength of surface sediments in the tidal flats were tested using a pocket vane shearing instrument with a range of 20 kPa (PS-VST-M, PENESON, Wuhan, China) and an electronic digital micro-penetration instrument with a range of 20 N (PS-MPT-A, PENESON, Wuhan, China), respectively. In addition, the plasticity index was determined with a liquid-plastic limit tester (LP-100D; SHANGYU GEOTECH, Shaoxing, China). Finally, compression tests were performed with a medium-pressure pneumatic automatic consolidation instrument (KTG-ZY; HUAKAN TECHNOLOGY, Beijing, China). Based on the knowledge of soil mechanics, the dry density, void ratio, and saturation were calculated. The particle-size composition was determined using conventional sieve analysis for the fraction of the sediment with a grain size greater than 0.063 mm, and the hydrosuspension method was used for the fraction of the sediment with a grain size less than 0.063 mm. For further details on the standard geotechnical tests, a soil mechanics book may be consulted (e.g., Bolton 1991).

Dynamic triaxial experiment
The Yellow River Estuary and adjacent Bohai Sea experience the most severe storm surges in the northern region of coastal China (Wang et al. 2012). The elements of waves with a recurrence interval of 50 years are often used for engineering analyses and calculations (Yang et al. 1995). However, the strong cyclic loading of waves with a 50 year recurrence interval is difficult to determine for the study area using general wave-generating experiments. Physical simulations mainly depend on dynamic triaxial experiments by setting the corresponding dynamic load amplitude and frequency. Here, we used the W3ZB-20 microcomputer-controlled hydraulic servo soil dynamic triaxial testing machine of the Ocean University of China (Qingdao, China) to conduct the dynamic triaxial experiments. This instrument uses stress-controlled vibrations and records the results (including dynamic stress, dynamic strain, and pore-water pressure) using photoelectric recorders. The size of the sample was 39.1 mm in diameter and 80 mm in height. The waveforms in the experiment included sine, triangular, square, trapezoidal, and random waves.
For each sample, we removed the original sample from the PVC sample tube and cut the sample into the required size. Then, the prepared sample was placed in a sample holder and fixed in a vacuum saturator for 1 h, after which water was added to the vacuum saturator until the triaxial experiment sample was covered, and the vacuum was applied for an additional 30 min. Finally, the vacuumed triaxial experiment sample was placed in water and let stand overnight.
The prepared saturated sample was placed in a three-axis pressure chamber for the loading consolidation experiment. This test used isostatic consolidation (i.e., consolidation stress ratio K c = 1.0). During the loading process, confining pressure (σ 1 = 45 kPa) and axial pressure (σ 3 = 45 kPa) were applied to simulate the stress environment of sediment at a depth of about 4 m. After completing the consolidation, the consolidation testing process was begun. In this test, we used drainage consolidation with a consolidation time of 2 h.
Next, a dynamic strength (i.e., liquefaction) test was performed. In this test, a cyclic dynamic load was applied to the sample. Waves act on the sea floor, producing a certain dynamic water pressure in the soil, which can be calculated with the following equations: where k is the wave number, ω is the wave angle frequency, H is the effective wave height, h is the water depth, and ρ ω is the sea water density (Yang et al. 1995). Based on the estimated wave elements of the Yellow River underwater delta with a 50 year recurrence interval (Table 1) (Jia et al. 2011b), the dynamic load amplitude σ d is 28 kPa to simulate the condition of waves with a 50 year recurrence interval in the experiments. The final conditions of dynamic triaxial experiment were a 5% double amplitude strain, dynamic load cycle period of 5 s, and vibration frequency of 0.2 Hz.

Data processing
Under the action of waves, the pore-water pressure of the seabed soil gradually increases, including the instantaneous pore pressure and the residual pore pressure. According to the way pore pressure is generated, the wave-induced soil response can be divided into two mechanisms: oscillatory and residual (Zen and Yamazaki 1990;Jeng 2018). The pore pressure obtained in this experiment is the sum of the cumulative pore pressure and the residual pore pressure, so when processing the pore pressure data, the maximum pore-water pressure and adjacent minimum pore-water pressure in each cycle were averaged, and plotted against the dynamic loading cycle number. In the analysis of axial deformation, the difference between the axial deformation corresponding to the maximum pore-water pressure and initial deformation value in each cycle was calculated. Thus, the curve of axial deformation against cycle number during the dynamic load action could be plotted, from which we determined the corresponding maximum axial deformation and minimum dynamic loading cycle number to the maximum pore-water pressure (u max ) of the original tidal flat sediment sample at each study site. In addition, the corresponding pore-water pressure and dynamic loading cycle number to the maximum axial deformation were determined.
Finally, the liquefaction degree (L d ) was defined as the ratio of excess pore pressure (u e ) to the final normal effective stress (P 0 ) under the dynamic load, where larger ratio values represent a higher degree of liquefaction. In the following equation: where P 0 was calculated using where γ′ is the submerged unit weight of sediments obtained from testing of soil samples, z is the depth of sediments where pore pressure was measured. In this test, the L d of a sediment sample under different test conditions was the ratio of the cumulative pore-water pressure of the sediment to the confining pressure (σ 3 ). The maximum L d of the sediment sample was defined as u max /σ 3 , where higher values represented greater sediment liquefaction.

Surface sediment properties
The conventional physical and mechanical properties of the sediment samples from the six study sites are shown in Table 2. The natural and dry densities were in the range of 1.89-2.01 g/cm 3 and 1.45-1.58 g/cm 3 , respectively, and the void ratios were 0.72-0.87, with small deviations. The natural water contents of the samples were 26.6%-33.0%. The saturations of the triaxial experiment samples were very high and similar (range: 96.34%-100%). Finally, the plasticity indices of the sediment samples were in the range of 5.3%-11.2%.
From basic mechanical property tests, the undrained shear strength and penetration strength were in the range of 3.2-8.8 kPa and 0.2-1.9 N, respectively, whereas the compression coefficients of the triaxial experiment samples were 0.120-0.169 MPa −1 , indicative of medium compressibility (Meckel et al. 2007).

Pore-water pressure response and sediment liquefaction
We collected samples from six sedimentary areas to conduct triaxial dynamic tests and study the sediment dynamic response in the deep layer (i.e., at 4 m). Notably, study sites S1 and S2 both formed during 1904-1929 but were in different erosional states, where S1 was slightly eroded and S2 severely eroded (Meng et al. 2012), with a rate of shore retreat of more than 56.6 cm/d (Jia et al. 2011b). These two study areas with distinguished erosion characteristics were chosen to study the erosion mechanism under extreme waves.
In the sediment samples from S1 and S2 (deposition period: 1904-1929), pore-water pressure increased rapidly during the initial stage of dynamic loading action and changed slowly for a short period, after which they remained stable (Fig. 3). Samples from S3 (deposition period: 1964-1976) and S6 (deposition period: 1947-1964) both showed three stages in their pore-water pressure curves. Samples from S5 (deposition period: 1929-1934) exhibited four variation stages in the pore-water pressure curve: a rapid increase, gentle increase, rapid increase, and stable period. In samples from S4 (deposition period: 1976-1996), pore-water pressure first rapidly increased, then slowly increased, and finally slowly decreased when the number of dynamic loading cycles exceeded 130, differing significantly from the other sample sites. Joint analysis of the deformation process of sediment samples under the dynamic loading action revealed consistent pore-water pressure variations that were closely related to the deformation process of the sediment dynamic response to wave loadings. For instance, pore-water pressure increased rapidly with minor deformation in the sediment samples collected from S5 within a load cycle number less than three, and the pore-water pressure increased slowly with very low deformation during load cycles 3-375; however, this slow rate of increase was still faster than the pore-water pressure growth rate during the second variation stage of the sediment samples from the other sedimentary lobes. At load cycles exceeding 375, pore-water pressure increased rapidly, reaching the confining pressure value at 650 load cycles, with a cycle period of 5 s, which indicated that sediment was completely liquefied under residual pore pressure. Therefore, seabed sediment at a confining pressure of 45 kPa could become completely liquefied under a wave load of 30 kPa for no more than 1 h, which could induce a fast linear increase in deformation with increasing numbers of cycles (Fig. 3e). Thus, widespread deformation failure of the seabed could occur under wave loading action of liquefied sediments. Xu et al. (2012) found a similar deformation pattern of the increase in sediment pore-water pressure for sediment deposited from 1929 to 1934 (site S5 in this study) under wave loadings based on dynamic triaxial experiments. Compared with the dynamic sediment responses at the other study sites in the present study, sediment deposited during 1929-1934 was unique in its characteristic of becoming completely liquefied under wave loading conditions. Therefore, the dynamic triaxial experiment results indicated that storm waves with a 50 year recurrence interval could completely liquefy the sediment to a depth of 4 m.
Comparing the pore-water pressure and deformation of samples S1-S4 and S6, the sediment at S2 ; without the influence of human activities) showed the lowest degree of deformation when the pore-water pressure increased to 4 kPa during the first stage of cyclic loading action, after which the deformation rate increased with increasing load cycles after 20 cycles; however, the deformation was still small at fewer than 250 load cycles. The deformation increased sharply when the pore-water pressure increased to 23 kPa, with the L d reaching 0.51. The variation in pore-water pressure and deformation indicated that the L d of sediment deposited at S2 at a depth of 4 m could exceed 0.5 under 50 year period storm wave conditions with continuous action of only 30 min. For comparison, deformation failure of the seabed with a sharp increase in sediment deformation can occur when 0.5 < L d < 1.0.
By contrast with S2, which was deposited in 1904-1929 and was not under anthropogenic influences, sediment at S1 was also deposited during 1904-1929 but was affected by human activities (e.g., dikes and dams). The pore-water pressure accumulation pattern and deformation process of S1 differed markedly from S2 but showed high similarity with S3 (deposition period: 1964-1976) and S6 (deposition period: 1947-1964). During the initial stage of dynamic loading action (<30 load cycles), pore-water pressure and deformation first increased rapidly and then gently, with minor pore-water pressure accumulation and a maximum L d of no more than 0.5 and maximum deformation of no more than 0.5000 mm within 700 load cycles. At S4 (deposition period: 1976-1996), the maximum L d was only 0.271. Overall, the results for these sediment deposits indicate that the seabed sediment at a depth of 4 m will not readily be eroded by waves from storms with a 50 year recurrence interval, with inconspicuous pore-water pressure accumulation for the sedimentary lobe deposited during 1904-1929 affected by human activities (i.e., site S1), and those deposited during 1964-1976 (S3), 1947-1964 (S6), and 1976-1996 (S4).

Discussion
Pore-water pressure model Based on the variations in pore-water pressure observed during the dynamic triaxial experiments on sediment samples collected from sedimentary lobes of the Yellow River Delta deposited during different periods, three general stages could be identified in the sediment pore-water pressure at a depth of 4 m under extreme sea conditions with a 50 year recurrence interval: a rapid increase, slow increase, and stable maintenance. Zeng et al. (2008) obtained a pore-water pressure accumulation model whereby sediment was fully liquefied during dynamic triaxial experiments based on the fitted normalized curve; however, this was not applicable to sediment with a low L d . Therefore, we created a new pore-water pressure accumulation model to describe the sediment dynamic response to wave loadings applicable to silty sediment in the modern Yellow River Delta.
In our model, the dynamic pore-water pressure (u) obtained in the dynamic triaxial experiments and the number of dynamic loading cycles (N) were normalized to construct the relation function of the ratio of dynamic pore-water pressure and confining pressure (u/σ c ) and the ratio of the number of dynamic loading cycles and the cycle number when the pore pressure is basically stable, which is obtained from experimental data (N/N s ) (see Table 3). Figure 4 shows the constructed pore-water pressure accumulation models that were applicable to the sediment dynamic response of the silty sediment deposited in different sedimentary lobes in the modern Yellow River Delta. The pore-water pressure accumulation curve is where a, b, and c are the test parameters, and are both dependent on the sediment type and properties. At the same time, the range of values of the variables in the equation depends on the triaxial test, N s > N > 0. Table 4 presents the values of a and b, as well as the standard error and squared correlation coefficient of the sediment pore-water pressure accumulation models for the six sampling sites in this study. From the results, the logarithmic curve model showed a good fit to the silty sediments in the modern Yellow River Delta, with a values of 0.34-0.63 and b values of 0.04-0.24 (except for study sites S4 and S5).

Influencing factors of sediment liquefaction
The maximum liquefaction index was used to numerically describe the degree of difficulty in achieving liquefaction for sediment under wave loading action, where larger values represent sediment that is more easily liquefied. Figure 5 shows the relationship between the maximum liquefaction index value and sediment parameters (i.e., sediment density, bulk density, water content, pore ratio, plastic index, average grain diameter, clay content, sand content, silt content, and sedimentary period) for seabed sediment at a depth of 4 m under storm conditions with a 50 year recurrence interval. Table 5 shows the Pearson correlation coefficient between the maximum liquefaction degree and the sediment parameters calculated using SPSS analysis software. The Pearson correlation coefficient is a statistic used to reflect the degree of linear correlation between two variables, indicating the degree of linear correlation between the maximum degree of liquefaction and sediment parameters.
Among the parameters, density, water content, and void ratio had relatively low influence on sediment liquefaction properties, as shown by the Pearson correlations, which are far less than one (Table 5) and the irregular curve describing their relationship with the maximum liquefaction index (Fig. 5). Sediment was more easily liquefied with increasing bulk density up to 1.55 g/cm 3 and less easily liquefied at bulk densities greater than 1.55 g/cm 3 . Similarly, the maximum liquefaction index values were observed at a pore ratio of 0.75 and plastic index of 8.3. Meanwhile, within the ranges tested in this study, the maximum liquefaction index was most affected by the average grain diameter, sand content, Maximum liquefaction degree = maximum pore-water pressure or confining pressure. and silt content, and clear monotone increases in the maximum liquefaction index were observed for average grain diameter and sand content and a monotone decreasing trend was observed with average grain diameter. Relatively speaking, the clay content and plasticity index have little effect, and both are negatively correlated with the maximum liquefaction index. Fig. 4. Mode of pore-water pressure accumulation for sediments collected from sampling sites S1-S6 in the Yellow River Delta under extreme sea conditions (i.e., waves with a 50 year recurrence interval). Solid blue circles, experimental results; red lines, fitted model. The influence of clay content showed two distinct stages on sediment liquefaction properties, where a clay content of 13% was the critical value, above which the maximum liquefaction index increased with increasing clay content. Xu et al. (2012) performed dynamic triaxial experiments on sediment samples with clay contents of 3%, 9%, 15%, and 21% and found an inflection point at a clay content of 9% on the development of pore-water pressure under dynamic loading actions; sediment with clay contents higher than 9% had a higher anti-liquefaction capacity (i.e., maximum liquefaction index) than sediment with a clay content lower than 9%, roughly consistent with the findings of a critical value at 13% clay content in this study. Meanwhile, in a flume experiment conducted by Liu et al. (2013b), waves had a high attenuation degree on seabed sediment with a high clay content     1904-1929 1929-1934 1947-1964 1964-1976 1976-1996  compared with sediment with a low clay content, which also indicated that sediment with higher clay contents liquefied less readily. In addition to the sediment's physical properties, sedimentary history (not considering human disturbance) was another important factor influencing sediment liquefaction properties. Sediments with an older deposition period had higher maximum liquefaction index values, the influencing mechanism of which could be jointly analyzed based on the influence of sediment particle size on sediment liquefaction and the evolution of sediment particle composition in the sedimentary history (Fig. 4). As shown by the close relationship between sediment particle composition and liquefaction, sediments with low clay contents could be more easily liquefied by wave loadings, while sediments with older deposition histories had lower clay contents due to the coarsening process of sediment under marine hydrodynamic conditions over time (Liu et al. 2013b(Liu et al. , 2017. Therefore, sedimentary history is an important factor in sediment liquefaction due to the resulting variations in sediment particle composition, which can directly affect sediment anti-liquefaction properties.

Conclusion
We conducted dynamic triaxial experiments on sediment samples collected from different sedimentary lobes with different deposition histories in the modern Yellow River Delta to study the sediment dynamic response to cyclic wave loading under extreme sea conditions with a 50 year recurrence interval. The following conclusions were derived.

1.
Sediments from different regions of the Yellow River Delta exhibit major differences in their dynamic response to extreme sea conditions. Although complete liquefaction of sediments could occur in the northern and southern delta regions (S2 and S5), the pore pressure would be unlikely to reach the confining pressure required for sediment deformation and destruction at the other study sites (S1-S4 and S6).

2.
The pore pressure response of sediments at 4 m to cyclic loading of waves with a 50 year recurrence interval could divide into three general stages: a rapid increase, slow increase, and stable maintenance. Thus, we proposed a logarithmic growth model of pore pressure, with parameters related to the sediment type and physical properties.

3.
Under extreme sea conditions with a 50 year recurrence interval, the plasticity index, mean particle size, and clay, silt, and sand contents of sediments in the Yellow River Delta have major effects on their liquefaction characteristics. In addition, the deposition history is an important natural factor in determining the resistance of sediments to liquefaction.
This study improved the existing prediction model for storm wave-induced liquefaction in a coastal seabed under anthropogenic effects. It is necessary to point out that the pore-water pressure response pattern proposed in this study is a simplified model that can be further improved in a more advanced field approach, although observing the pore-water pressure in situ under extreme storm sea conditions can be challenging. The preliminary findings presented in this paper can be further used in engineering analyses to assess the safety and support disaster prevention efforts in geotechnical engineering projects.