Coastal Engineering Construction Research Articles

Simplified models of wind-wave relationships in China's shallow-water coasts based on SWAN+ADCIRC simulations

The study of the shallow-water wind-wave relationship holds considerable importance in the realm of coastal engineering construction. However, existing empirical formulas for China's coastal areas face predictive accuracy challenges due to the discontinuity and insufficient temporal and spatial resolution of conventional observations, such as buoy and satellite data. Therefore, this study emphasizes two representative shallow-water areas along China's coast, the Pearl River Estuary and Bohai Bay. Based on the advanced SWAN + ADCIRC wave-current coupling model, numerical models for calculating wave evolution are established, calibrated and validated by real observation data. From these numerical foundations, a new model capturing shallow-water wind-wave relationship is proposed, demonstrating substantive applicability specifically tailored to the estuary and bay regions. The accuracy and applicability of the model are validated by comparing with real observation data. In addition, probabilistic models are introduced in this study accounting for the randomness of the significant wave height. These enhancements allow for refined quantification of significant wave height occurrence probabilities relative to specified wind speeds, offering informed predictive parameters, including upper and lower limits.

Undrained dynamic behavior of geogrid-reinforced coral sand

In this research, the reactions of geogrid reinforcement on the dynamic performance of medium-dense coral sand with various cyclic stress ratios were investigated using stress-controlled undrained dynamic triaxial tests. The results indicate that the insertion of geogrid decreases the dynamic deformations, and pore pressure build-up rate, and impeded the liquefaction of coral sand. The liquefaction resistance of coral sand increases with the increase in the number of reinforcement layers. The liquefaction resistance of coral sand reinforced with three-layer and two-layer geogrid increases by 333% and 6% compared to unreinforced ones. The geogrid reinforcement layers can effectively resist the complete stiffness degradation of coral sand under cyclic loading. The coral sand stiffness decays at an accelerated rate as the cyclic stress ratio increases, whereas increasing the number of reinforcement layers reduces the coral sand stiffness degradation rate, especially for three-layer geogrid reinforced coral sand at low cyclic stress ratios. Generally, the geogrid as a reinforcement material to coral sand is considered a better alternative to enhance the engineering properties of coral sand and offers significant prospects in coastal and marine engineering construction with coral sand.

On the Legal Liability of Coastal Engineering Construction Projects not Conducting Environmental Impact Assessment by the Law of Marine Environmental Protection

On the Legal Liability of Coastal Engineering Construction Projects not Conducting Environmental Impact Assessment by the Law of Marine Environmental Protection

Assessment of Ocean Circulation Characteristics off the West Coast of Ireland Using HF Radar

Research on coastal ocean circulation patterns over long time periods is significant for various marine endeavors: environmental protection, coastal engineering construction, and marine renewable energy extraction. Based on sea surface current data remotely observed using a shore-based high frequency radar (HFR) system for one year (2016), spatiotemporal characteristics of surface flow fields of sea surface flow fields along the west coast of Ireland are studied using harmonic analysis, rotary spectral analysis and representative flow fields over different seasons and the whole year. Coastal surface currents in the study area are strongly affected by tidal dynamics of the M2 constituent, showing significant characteristics of regular semidiurnal tide, such as M2 and S2. The energy spectrum distribution indicates that the tidal constituents M2 and S2 are the dominant periodic energy constituents in a counterclockwise spectrum, which mainly presents rotating flow; the representative diurnal tidal constituents is the constituent K1, and its energy spectrum distribution is mainly clockwise. A comparison between probable maximum current velocity (PMCV) and measured maximum current velocity (MMCV) is presented. It shows that although tidal current characteristics in the study area are significant, the main driving force of the currents at the time of the maximum currents is wind energy. These results provide new insights into a region of huge societal potential at early stages of sustainable economic exploitation where few data currently exist.

Research on the breakage and fractal characteristics of calcareous sand

Calcareous sand is widely used in coastal engineering and island construction, which has the characteristic of easy crushing. A series of ring shear and one-dimensional compression creep tests were carried out for the crushing evolution under the influence of large deformation and time length effects. The mechanical characteristics and deformation properties of the single-graded specimens were analyzed, focusing on the crushing characteristics, and fractal properties under the action of different shear displacements, stress levels, initial gradations and creeping motion effects. The results show that the fractal dimension is positively correlated with crushing, the increase of shear displacement, stress level, and initial mean particle size has a facilitating effect on crushing. Under large deformation conditions, this promoting effect gradually tends to slow down, and the characteristic of limit fractal exists. The creep behavior reflects the continuous deformation characteristics of calcareous sand, and the specimen as a whole is still in the stage of crushing development, and the effect of time duration on the fractal is limited.

Assessing the liquefaction potential of seabed soils based on ocean ambient noise in the Yellow River Delta

Seabed soils can undergo liquefaction under cyclic loading, resulting in a rapid decrease in strength and stiffness, which may lead to the destruction of offshore structures. Therefore, the assessment of seabed soil liquefaction will become an important factor in disaster prevention and risk analysis in coastal and offshore engineering construction. In this study, the ocean ambient noise with low-frequency, long-wavelength, and wide-band characteristics was used to conduct and analysis noise based on the horizontal-to-vertical spectral ratio method. The shear wave velocity of the seabed soil was obtained by inverting the ocean ambient noise dataset. Then, we proposed a shear wave velocity threshold that can be used for liquefaction assessment of Holocene unconsolidated fine-grained soils by statistical analysis, and the liquefaction potential of the soils was evaluated according to 1-D shear wave velocity structures and 2-D shear wave velocity profiles. The results showed that the distribution of the shear wave velocity obtained by inverting ocean ambient noise was generally consistent with the measured shear wave velocity in the field, indicating that the inversion results have a certain degree of accuracy. A shear wave velocity threshold of 200 m/s was proposed for liquefaction assessment, determining that the soils within 0-10 m depth in the coastal area of Yellow River Delta have liquefaction potential. This result is in accordance with the assessment based on the critical shear wave velocity, indicating that this threshold is applicable to the assessment of seabed soil liquefaction in the Yellow River Delta. The in-situ observations of ocean ambient noise provide a more convenient, economical, and environmentally friendly method, which can help to investigate marine geology disasters and serve marine engineering construction.

Direct shear behavior of dredged soil under dynamic normal load conditions

Dredged soil is commonly encountered in estuarine and coastal engineering constructions; however, its dynamic frictional behavior is still unclear. In this research, DJZ-500 shear apparatus was utilized for conducting direct shear test on the dredged soil. The periodic normal stress was employed in the vertical direction of soil sample, and simultaneously, shear stress was applied in the horizontal direction to supply a constant speed. The influences of different shear rates, dynamic normal stress frequencies, and dynamic normal stress amplitudes on the shear properties of the dredged soil under dynamic normal stress conditions were explored. It was found that shear stress periodically varied with the periodic normal stress, characterizing a phase lag with the peak shear stress. The dynamic normal stress manifested an enhancement effect and also a weakening effect on the shear strength. Generally, a small dynamic normal stress frequency, a high shear speed, and an appropriate dynamic normal stress amplitude induced frictional strengthening, whereas a small shear speed, a large dynamic normal stress frequency, and a very large or small dynamic normal stress amplitude caused frictional weakening. Therefore, the dynamic frictional behavior of the dredged soil depended on shear velocity and the frequency and amplitude of dynamic normal stress. The results of this paper provide technical support to improve the resistance of coastal constructions to dynamic disturbances, such as earth tides, ocean waves, earthquakes, typhoons, and traffic loads.

Advances in Marine Engineering: Geological Environment and Hazards

With the continuous advancement of coastal, offshore, and deep-sea engineering construction (e [...]

End-member characteristics of sediment grain size in modern Yellow River delta sediments and its environmental significance

IntroductionThe sediments of the Yellow River delta record the environmental changes in the Yellow River basin on a long time scale and are sensitive to the river diversion and sedimentary environment evolution.MethodsIn this study, cores YDC and YDG in the delta near the estuary of the Yellow River since 1976 were taken as the research object, and the parameterized end-member analysis model was used to analyze the grain-size data of the cores.ResultsThe results show that: The main sediments were silty and sand (58% and 77.9%). The grain-size parameters showed opposite changes with wide grain-size ranges and mixed sizes obviously. End member 1 (EM1) and end member 2 (EM2) were composed of clay and fine silt with fine particle sizes of 0.04 mm and 9.8 mm, respectively, and were deposited under weak hydrodynamic conditions during long-distance transport along the Yellow River. End member 3 (EM3) and end member 4 (EM4) were coarse silt with mode particle sizes of 40.14 mm and 66.89 mm, respectively. These were deposited by waves and tidal currents under strong dynamic conditions.DiscussionAccording to the channel changes and the sedimentary facies data of the modern Yellow River delta, before the Yellow River was diverted in 1996, the cores YDC and YDG were both in the estuary-front bar sedimentary environment. In 1996, the Yellow River was diverted to the Qing 8 course. Subsequently, the core YDC changed to the delta-plain sedimentary facies, and the core YDG changed to the delta-front facies. The sediment sources of the two cores changed from the Yellow River sediments to coastal sediment erosion and resuspension. The sedimentary environment changed from siltation to erosion. The results of this study are of great practical significance for estuary management and coastal engineering construction in the modern Yellow River delta and can provide a scientific basis for ecological protection and high-quality development of the Yellow River basin.

In situ observation of wave-induced deformation of submarine landslides in tidal channel areas

Landslides often occur in land slopes, estuaries, fjords, and intertidal zones in the marine environment, while landslides in tidal channels have not been systematically reported. The Zhoushan sea area is dotted with islands and crisscross tidal channels, which is a typical tidal channel development area. The data from the coastal zone and island survey, offshore engineering site selection, and environmental survey show that landslides are very common in tidal channel areas. The detailed study of this kind of landslide will enrich the research theory of submarine landslide and have important guiding significance for marine planning, development and site selection, and construction of coastal engineering in coastal areas. First, the submarine landslide in southwest of Zhujiajian Island in Zhoushan is investigated in this study. It is found that the sliding zone is parallel to the island coastline, with a length of about 250 m and an extension of 2 km, and the buried depth of the sliding surface is generally 8–10 m; then, through the self-developed seabed deformation observation system, combined with the hydrodynamic observation system, the landslide was observed in situ for 75 days. The observation results showed that the landslide slides at a constant speed along the sliding surface under the action of weight; the slides accelerate under the action of waves, and multiple sliding surfaces are generated in the landslide body at the same time. Finally, the genetic mechanism of submarine landslides in tidal channel areas is put forward.

Spatial and temporal characteristics analysis for land subsidence in Shanghai coastal reclamation area using PS-InSAR method

In recent decades, large-scale reclamation projects have been performed in the intertidal flat area of Shanghai, China. Due to the self-weight consolidation of the foundation and dynamic load caused by human activities, the newly reclamation area will sink within a period of time after the land is formed. Therefore, it is necessary to carry out surface deformation monitoring for taking preventive measures in advance. In this research, the PS-InSAR technology, mostly used for urban subsidence monitoring, was applied to obtain the ground deformation information of Shanghai coastal area based on ENVISAT/ASAR (2007.07-2010.02) and Sentinel-1A (2017.07-2020.02) datasets. The results showed that: 1) Compared with ASAR data, the Sentinel-1A data could distinguish more coherent points and get more comprehensive deformation distribution characteristics. 2) Most high-coherent points were detected in artificial objects, especially airport runways, buildings, roads and seawalls. 3) There was obvious uneven land subsidence in the study area during the two monitoring periods, the PS points with high subsidence rates (<-20 mm/a) mainly distributed around Dishui Lake and artificial seawalls. 4) The ground subsidence velocity of the newly formed land gradually slowed down over times, with the average subsidence rate decreased from -10.45 mm/a to -4.94 mm/a. Our study proved that remote sensing monitoring for ground subsidence in reclaimed land could be realized based on PS-InSAR technology, which could provide the spatial distribution characteristics of subsidence in large-scale and long-term series and help the sustainable development of coastal engineering construction.

The spatio-temporal distribution and transport of suspended sediment in Laizhou Bay: Insights from hydrological and sedimentological investigations

Suspended sediment transport and deposition are crucial physical processes controlling the geomorphological evolution of estuaries and bays. Specially, under the context of worldwide coastal erosion, knowledge of the spatio-temporal distribution of suspended sediment concentration (SSC) and its associated sediment load have become increasingly important for bay management. However, our understanding of the mechanisms of suspended sediment dynamics continues to be hampered by the lack of high-resolution observations. Here, we present a study of the transport mechanisms and controlling factors of suspended sediment over Laizhou Bay. For this, we conducted continuous measurements of SSC, salinity, temperature, and flow velocity at nine stations throughout Laizhou Bay for one 25-h period during each of the spring and moderate tides. Based on these data, residual current, gradient Richardson numbers, and suspended sediment flux were calculated. Our results indicate that a strong current field occurs near the Yellow River mouth, corresponding to the zone with high SSC. The overall diffusion characteristics of suspended sediment are controlled by the tidal current field. Furthermore, our findings suggest that different degrees of stratification occur in the water column, which inhibit the effective vertical diffusion of suspended sediment; Higher water temperature was the main cause of stronger water column stratification of spring tide than moderate tide. Finally, our results reveal that the type of seabed sediment is an important factor controlling SSC by influencing resuspension flux. We conclude that the primary mechanisms controlling suspended sediment transport in Laizhou Bay are advection and tidal pumping, especially advection. Our research provides both a foundational reference for the sediment source-to-sink process from the Yellow River to the sea, as well as guideline implications for coastal engineering construction and channel dredging.

Wave Dissipation and Sediment Transport Patterns during Shoreface Nourishment towards Equilibrium

Implementing shoreface nourishment is an effective method to protect sandy beaches. A better understanding of the equilibrium mechanism of shoreface nourishments is necessary for coastal engineering designs and constructions. Two experiments on the beach profile equilibrium of the shoreface nourishment are carried out under mild wave conditions on the reflective and intermediate beach. It is observed that the shoreface nourishment increases local wave height and strengthens wave nonlinearity by its shallow water depth. The most intense wave breaking dissipation has been found on the crest of the shoreface nourishment, and the distribution of wave energy dissipation rate is more uniform on the quasi-equilibrium profile than that on the initial profile. A process-based numerical model is used to reproduce bed profile evolution successfully. On that basis, it is found that onshore bedload transport is the primary cause for the onshore migration of the shoreface nourishment. The magnitude of bedload transport decreases during the evolution of the shoreface nourishment towards equilibrium. The most intense sediment transport rate occurs over the shoreface nourishment or in front of the shoreline, depending on the ’lee effect’ of the nourishment. Furthermore, the effects of incident wave height, wave period, and sea-level rise on the equilibrium profile of the shoreface nourishment under mild wave conditions are analyzed.

Effect of waste rubber particles on the shear behaviour of bio-cemented calcareous sand

Calcareous sand, a special type of sand commonly used for the construction of coastal engineering in tropical coasts, is usually required to be strengthened due to its poor engineering mechanical properties. Microbially induced carbonate precipitation has been proved to be a promising method for this purpose. A higher cementation level generally leads to a greater strength enhancement, but tends to cause brittle failure of bio-cemented calcareous sand, which in turn brings great potential risks for the coastal engineering. Therefore, the shear behaviour, especially the brittle behaviour, of bio-cemented calcareous sand needs to be understood properly, and taking some measures to improve its brittle behaviour is also necessary. In this regard, a series of triaxial compression tests were conducted to study the shear behaviour of bio-cemented calcareous sand with various cementation levels, and the waste rubber particles are used to improve the brittle behaviour of bio-cemented calcareous sand. The test results show that the shear strength of bio-cemented calcareous sand increases with the increase in cementation level, and the brittle behaviour is significant gradually. The waste rubber particles contribute to improve the brittle behaviour of bio-cemented calcareous sand, reducing the dilation of bio-cemented calcareous sand and slowing the changes in dilatancy with the increment of stress.

A Spatiotemporal Change Detection Analysis of Coastline Data in Qingdao, East China

This study focuses on the coastal features, environments, and dynamics to accurately describe and regularly monitor the Qingdao shoreline in eastern China. It collects categorical ETM+ and OLI data from 2000, 2010, and 2019 on the mainland coastline and explores the characteristics and spatiotemporal differences across the past 19 years by using remote sensing and geographic information system (GIS) technologies. The results show that the length of the Qingdao coastline has increased continuously over the last two decades, for a total increase of 18.14 km. There are different natural and artificial coastlines that have undergone major changes. The human-induced deterioration of coastlines has gradually and substantially risen from 53.63% in 2000 to 68.40% in 2019, while the length of the natural coastlines has decreased dramatically. Jiaozhou Bay focuses on areas with significantly changing coastlines, and major changes have occurred in the west and east of the Qingdao coast. The coastline has largely expanded seaward because of the comprehensive impact of natural and anthropogenic factors. The leading factor in coastal evolution is coastal engineering constructions. In addition, the top three other construction activities are the restoration of the aquaculture pond, salt field, and harbor edifices. The driving force that triggered the shift in the coastline reveals significant temporal heterogeneity.

Consolidation and Deformation Characteristics of Soft Rock Foundation in Hydrological Wetland Environment

The widespread distribution of soft rock and soft soil in hydrological wetland environment is a common geotechnical engineering problem encountered in coastal engineering construction. To solve this problem, a study method for consolidation and deformation characteristics of soft rock and soft soil foundation in hydrological wetland environment is proposed. Taking K9+280-K11+120 section along Fu-Nehe section of National Highway 111 as the research object, the consolidation and deformation characteristics and loading conditions of soft soil foundation under embankment filling load, treatment methods of soft rock foundation, stratum conditions, temperature changes and time effects are analyzed. The results show that although the wetland soft rock and soil layer is not thick, the settlement of soft rock and soil accounts for more than 80% of the total settlement. Negative temperature has a certain influence on the consolidation settlement of soft rock foundation, which is mainly manifested in the difference between the settlement process of the central separation zone and the roadbed soft soil foundation; the pore water pressure of soft rock foundation dissipates to varying degrees. According to the monitoring results of settlement and pore water pressure, bagged sand wells are more suitable for soft rock foundation engineering treatment in hydrological wetland. The research results can provide a reference for the study, calculation and design of consolidation and deformation of soft rock foundation in hydrological wetland.

Retrieval of Nearshore Bathymetry around Ganquan Island from LiDAR Waveform and QuickBird Image

Optical remote sensing is an effective means of water depth measurement, but the current approach of mainstream bathymetric retrieval requires a large amount of onsite measurement data. Such data are hard to obtain from places where underwater terrains are complicated and unsteady, and from sea areas affected by issues with rights and conflicts of interest. In recent years, the emergence of airborne light detection and ranging (LiDAR) provided a new technical means for field bathymetric survey. In this study, water depth inversion was carried out around an island far from the mainland by using remote sensing images and real LiDAR waveform data. Multi-Gaussian function fitting was proposed to extract water depth data from waveform data, and bathymetric values were used as control and validation data of the active and passive combination of water depth inversion. Results show that the relative error was 5.6% for the bathymetric retrieval from LiDAR waveform data, and the accuracy meets the requirements of ocean bathymetry. The average relative error of water depth inversion based on active and passive remote sensing was less than 9%. The method used in this study can also reduce the use of LiDAR data and the cost, thus providing a new idea for future coastal engineering application and construction.

Dynamic Prediction Method for Slope Slip Rate of Geotechnical Engineering in Coastal Zone

Zhang, H., 2019. Dynamic prediction method for slope slip rate of geotechnical engineering in coastal zone. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 512–517. Coconut Creek (Florida), ISSN 0749-0208.The characteristics of slope slip rate of coastal geotechnical engineering are extracted and analyzed in different environments, the geological characteristics of coastal geotechnical are reconstructed, and the prediction of slope slip rate of coastal geotechnical and the construction of coastal geotechnical engineering are realized. A prediction method for slope slip rate of coastal geotechnical engineering based on fuzzy C-means clustering method is proposed to identify the lithologic characteristics of coastal rock and soil. Firstly, the spatial triangulation method is used to extract the scattered data of the geological layer of the rock and soil in the coastal zone, and the data fitting model of the slope slip rate interpretation of the lithology of the rock and soil in the coastal zone is constructed. The improved FCM method is used to classify the extracted data of slope slip rate of geotechnical engineering in coastal zone, so as to realize the adaptive clustering of lithologic properties of rock and soil in different coastal zones. According to the environmental change, vector cutting is carried out on the regional layer surface of the coastal rock and soil, and the dynamic prediction of the slope slip rate of the geotechnical engineering in the coastal zone is realized. The simulation results show that this method has high accuracy in classification of soil slip rate and prediction of slope slip rate in coastal zone geotechnical engineering, and can realize the construction of geotechnical engineering and landslide control in coastal zone.

Modeling Study on the Hydrodynamic Environmental Impact Caused by the Sea for Regional Construction near the Yanwo Island in Zhoushan, China

Waves are one of the most important factors affecting offshore marine engineering. Accurate calculation of wave distribution is an important prerequisite to ensure the safety of coastal engineering construction. Due to the influence of complex topography, hydrological conditions, and marine structures on the propagation of waves offshore, slowly varying topography, refraction, diffraction, reflection, shallowness, and other phenomena may occur. This article combines the MIKE21 Spetral Waves (SW) wave model and the MIKE21 Boussinesq Waves (BW) wave model which are developed by Danish Hydraulic Institute (DHI) for a joint application (SW–BW nested model). It simulates the hydrodynamic environment of the Yanwo Island scenic area, located in Zhoushan, in both large and small ranges. In addition, wave height distribution and berthing stability of different breakwater planning schemes are calculated to optimize the layout of the breakwater. Through the analysis of simulation results, it is concluded that the hydraulic performance of Scheme 2 (the broken line section on the west side is 100 m long, and that on the east is 1200 m long, and the breakwater is rotated 8 degrees counterclockwise along the axis on the basis of Scheme 1) is better than that of Scheme 1 (the broken line section on the west side is 100 m long, and that on the east is 1100 m long), which can provide a more reliable construction reference for the construction of the Yanwo Island scenic area.

Acoustic Emission and Force Drop in Grain Crushing of Carbonate Sands

AbstractThe crushing behavior of carbonate sand, due to its porous and fragile structure, exerts a significant influence on the construction of coastal engineering. The collapse of porous material ...