| With the continuous development of economic growth and scientific and technological levels,humans need more transportation methods to adapt to the rapidly developing society.Canals are one of the most important engineering projects in human history,with important economic,cultural,and strategic significance.They are still the main transportation method between regions today.Pinglu Canal is an important carrier for the construction of the Western Route of the Land-Sea New Channel,which is an important channel for the comprehensive opening-up of the Western Region.The construction of Pinglu Canal is an important step and also relevant to the long-term development plan of Guangxi,which is an indispensable important support for Guangxi to achieve its development goals.With the construction of Pinglu Canal Project,it is inevitable to cause changes in water dynamics,suspended sand diffusion and so on,which will lead to changes in the water environment within Pinglu Canal,thus affecting the changes in the sea environment and ecological environment in the area.In recent years,the protection of mangroves has become an indispensable focus of the coastal economic development policy of Guangxi.The Beibu Gulf of Guangxi has rich mangrove resources,so exploring the impact of the construction process of Pinglu Canal on the water dynamics and suspended sand diffusion of Qinjiang River Navigation Channel and the mangroves around Qinzhou bay has great significance.This article focuses on the changes in hydrological conditions before and after the construction of Pinglu Canal and the underwater geography changes during the operation stage,and studies the impact of the construction process of Pinglu Canal on the water dynamics,suspended sand diffusion,and ship traffic during operation of Qingjiang River Navigation Channel and the mangroves around Qinzhou bay,providing data support and technological support for the construction of the canal and the utilization of ocean resources.This article based on the collected site information,hydrological data,engineering reports,and other sources,used a two-dimensional mathematical model to calculate the changes in hydrodynamics before and after the construction of the Pinglu Canal engineering project,the degree of diffusion of suspended sands under different source strengths and locations,the thickness of sand deposition,and the height of ship-borne waves during operation.The article also explored the impact of the surrounding Mangrove forest on these phenomena,and the main conclusions are as follows:(1)Based on the results of calculating and measuring the tidal level,current velocity and phase,the numerical tidal flow model and selected parameters are considered to be suitable,which can reflect the flow propagation process and flow movement law of the sea area near the project area,and provide necessary conditions for further analysis of the flow field and sediment transport simulation after the project.(2)The tidal current field in Qinzhou Bay and Qinzhou River Basin changed to varying degrees after the project.The tidal current movement in Qinzhou Bay was mainly in the form of re-current,and the flow field in the waterway area was basically consistent with the trend of the waterway.Only the velocity increased in some areas,and the closer to the project area,the more obvious it was.(3)Before the implementation of the project,the distribution of surge and fall jet fields is basically the same as before.The basic characteristic is that the ebb tide velocity is higher than the ebb tide velocity.After the implementation of the project,it mainly affects the local sea area where the project is located.The overall tide and ebb trend of the sea area are not changed,and the overall flow field of the sea area is basically unchanged before and after the implementation of the project.(4)In this study,the suspended sediment with a concentration increment of 2mg/L basically reached the maximum area of the mangrove forest within 15 tidal cycles after construction,in which the source intensity was 8.79 kg/s and the position D1 reached the maximum area in the 17th tidal cycle due to the obstruction of the bed width and island in the Qinjiang River basin.The working condition with position D2 reaches the maximum value in the 6th tide cycle,and the remaining working conditions all reach the maximum value in the 12th～13th tide cycle.(5)Under different source intensification conditions based on location D3,when the concentration increment is 10 mg/L of the four types of water quality,the maximum area of mangrove affected is 8.79 kg/s 0.1405 km~2)>5.4 kg/s(0.002km~2)>2.32 kg/s(0 km~2),and when the concentration increment is 2 mg/L,The maximum area of mangrove was 8.79 kg/s 0.3 038 km~2)>5.4kg/s(0.2 796 km~2)>2.32kg/s(0.2 193 km~2).According to the results,the area of mangrove affected by suspended sediment diffusion was positively correlated with the intensity of source intensity.(6)Results of scouring and silting in this study through calculation and analysis of predicted results,it can be concluded that suspended sediment deposition under all working conditions is not enough to cause mangrove death,but attention should be paid to D1 position closest to mangrove.(7)Based on the experimental data,it is concluded in this study that the propagation of ship traveling waves near the shoreline has attenuated,and the sedimentation rate of suspended particles in water is fast.Suspended particles caused by ship traveling waves are difficult to be transported to other sea areas,and will not have a significant impact on the sedimentation of coastal mangrove areas. |
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