Spatio-temporal variation of subtidal macrobenthic fauna and the ecological assessment of Longkou Artificial Island construction in Bohai Sea, China

To evaluate the status and changes of macrobenthic communities related to the construction of the Longkou Artificial Island(LAI)in the Bohai Sea,China,four annual surveys were conducted from 2010 to 2013.Significant changes on environmental variations and macrobenthic communities were observed in 2013 after the LAI construction a couple of years later.The changing environment was primarily presented by lower values of pH,dissolved oxygen(DO),organic material(OM)percentage,and higher salinity,suspended particulate matter(SPM)concentration and oil concentration.The main dominant species shifted from Polychaeta taxa in 2010 to Mollusca taxa in 2013 due to the changes of environmental variables.An apparent miniaturization tendency in body size of macrobenthic species was presented from 2010 to 2013.The biodiversity indices increased yearly from 2010 to 2013.However,inter-site homogenization was observed in both the community structure and health status.Multivariate AZTI Marine Biotic Index(M-AMBI)analysis showed that the health status of stations changed depending on its original status and distance to the LAI.However,no significant differences were found in the spatial distribution of either environmental variables or abundance,biomass and biodiversity of macrobenthic communities.All the results will provide a basis for the long-term ecological assessment of reclamation.

Effects of offshore artificial islands on beach stability of sandy shores:case study of Hongtang Bay,Hainan Province

Artificial island-type reclamation often exerts certain impacts on near-shore sandy shoreline resources and coastal ecological landscapes.The relationship between artificial islands and offshore beach evolution has attracted considerable attention in coastal protection and engineering construction.In this study,we consider Hongtang Bay in Hainan Province,China,as the research object.We adopted the Gao-Collins model to investigate the substrate transport trend in this sea area based on the analysis of the measured hydrologic and sediment data.The shore section from Nanshanjiao to Hongtangling(Taling),including the flat and straight shore sections,is dominated by the lateral transport trend of the vertical shore.The near-shore water has a strong lateral sediment transport capacity,while the outer deep-water area exhibits a sediment transport trend consistent with the tidal current movement.Using multi-year topographic data,the shoreline and seabed alterations in Hongtang Bay were analyzed,and the LITLINE beach evolution model was adopted to simulate the effects of three artificial island layouts with different island filling areas,offshore distances,and plan forms on the near-shore shoreline deformation.The results obtained indicate that the artificial island arrangement with a large offshore distance and a small area has relatively substantial advantages,such as minimizing the adverse effects of artificial island implementation on the near-shore beach.

Drivability of Large Diameter Steel Cylinders During Hammer-Group Vibratory Installation for the Hong Kong–Zhuhai–Macao Bridge

The Hong Kong–Zhuhai–Macao Bridge(HZMB)involved the installation of 120 mega-cylinders with a diameter of 22 m,weights up to 513 t,and penetration depths up to 33 m using an eight-vibratory hammer group.Due to the lack of engineering experience on the drivability of large-diameter cylinders under multiple vibratory hammers,predicting the penetration rate and time of steel cylinders is an open challenge that has a considerable impact on the construction control of the HZMB.In this study,the vibratory penetration of large-diameter steel cylinders in the HZMB is investigated based on geological surveys,field monitoring,and drivability analysis.The vibratory penetration rate,installation accuracy,and dynamic responses of the steel cylinders at both the eastern and western artificial islands are analyzed.The dynamic soil resistance has a great influence on the cylinder drivability.However,the current design methods for estimating the vibratory driving soil resistance are proven inaccurate without considering the scale effects.Therefore,a modified method with a normalized effective area ratio A_(r,eff)is proposed in this study to calculate the vibratory soil resistance for open-ended thin-wall cylinders under unplugged conditions.Considering the scale effects on the vibratory driving soil resistance,the proposed method leads to closer results to the measured data,providing a reference for future engineering practice.

NUMERICAL SIMULATION AND EXPERIMENTAL STUDY OF THE FLOW FIELD AROUND A CIRCULAR CYLINDRICAL ARTIFICIAL ISLAND UNDER THE ACTION OF WAVES AND VISCOUS CURRENT

Experimental study and theoretical research were described in the paper on the characteristics of the flow field around a vertical circular cylindrical artificial island under the . action of waves and viscous current. Flow field and hydrodynamic coefficientS of an artificial island under the action of waves and viscous current were computed and compared with those for the cases of pure viscous current and pure incident waves and those of measured resultS with good agreement.