ABSTRACT

The layout of the sludge discharge pipeline is an important part of the dredging project. The commonly used floating pipes are often subject to wind and sun erosion during use, and the use of floating pipes for dredging operations in navigable waters can affect the normal navigation of other ships. Most of the existing sinking pipes are used in shallow inland waterways.. Therefore, this study proposes the feasibility of laying and construction of a large water depth (50 m) pipe sinking in view of the shortcomings of the existing dredging pipe technology. In this paper, theoretical analysis and numerical simulation were mainly used to analyze and calculate the laying and construction stages of a large deep water sinking pipes. The results showed that the error between the numerical simulation results and the theoretical analysis results was small, indicated that the calculation results had certain reliability; The sinking pipe slowly sinks during the laying process, and the pipelines at the bottom successively sink to the bottom, and finally become stable; The maximum stress point of the whole pipeline was located at the connection between the floating pipe and the transition pipe section; According to the maximum stress of relevant components at key parts of the pipeline transition section during pipe sinking and construction, further stress and strength analysis of materials were carried out, and the maximum yield stress and tensile stress of bolts were 34.72 Mpa and 58.18 Mpa respectively, and the maximum stress of rubber pipes was 6.45 Mpa, both within the limit stress range of materials. It shows that the 50 m deep water pipe can run normally under the design condition and can be used in practical projects.

INTRODUCTION

In the dredging and reclamation project, the sludge discharge pipeline is an important part of the dredging construction process. According to the location and basic functions of the dredged sludge pipes, Zhang(2020)had compared the differences of hydraulic reclamation pipelines used by dredging companies in China and Europe, mainly could be divided into floating pipes, sinking pipes and onshore pipes. In addition to the laying form of the dredge pipe, Yan(2014) thought that the material selection of the dredge pipe was also crucial. Yang(2021) and Qin(2002) have studied the floating pipe through numerical simulation and test, and found that the stability and anti-wind and wave capacity of the self-floating mud pipe are better than those of the pontoon mud pipe. But there were two main structural forms of floating pipes, one is to wrap plastic floating sheets on the outside of the steel sludge discharge pipe, the second is to float on the water surface after being connected in series with steel pipes through steel pipes and armored pipes or rubber floating pipes. When dredgers or trailing suction dredgers carry out reclamation construction in navigable waters, the floating pipes used will hinder the normal navigation of ships. At present, most of the underwater sinking pipelines used are only applicable to shallow river courses, flat river beds, slow flow areas with little scouring and silting. However, with the development of social economy, the throughput of wharves built by countries around the world is increasing, and the corresponding ships are also increasing, and the draft is getting deeper and deeper. The existing underwater sinking technology can not meet the current requirements for normal navigation of ships in large seaports and deep-water channel areas. In combination with the existing construction ships and project projects, Xiong(2015), Lv(2021) and Feng(2020) had established a slurry pipeline transportation model to provide guidance for the route planning and hydraulic characteristics analysis of similar long distance hydraulic fill pipelines. According to the two laying schemes of immersed pipe crossing the channel, Lu(2022), Feng(2018) and Hu(2014) putted forward the key points of the construction technology of immersed pipe laying through comprehensive analysis and comparison, providing reference experience for the optimization and selection of immersed pipe laying schemes and the construction technology of immersed pipe laying in similar projects.

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