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Yuan, Chaozhe (National Engineering Research Center of Dredging Technology and Equipment) | Wang, Feixin (National Engineering Research Center of Dredging Technology and Equipment) | Tao, Runli (National Engineering Research Center of Dredging Technology and Equipment)
ABSTRACT In order to solve the problem of large error between the coase sand pipeline transportation resistance calculated by Durand Formula and the measured value, a field test was carried out in a certain project. Based on the measured data, combined with the mathematical statistical analysis method, the optimization of Durand formula has been realized. The conclusions are given: the optimized formula can well characterize the pipeline transportation characteristics of the coarse sand, achieve high-precision & real-time prediction on the construction site, and the calculation method of the critical flow velocity with minimum friction is given. INTRODUCTION In the land reclamation engineering, CSD and TSHD are mainly used to the filling construction. And the pipeline transmission is an important link, and the loss of pipeline pressure is an important research content of pipeline transportation characteristics. The current methods used for pipeline transportation resistance prediction is mainly based on three different theories (Fei, 1994, Fei, 1986): diffusion theory, gravity theory and energy theory. The representative empirical formulas based on the above methods are Durand formula, Wasp formula, Wilson formula, Fei Xiangjun formula, Wang Shaozhou formula, Chen Wenguang model, etc., and all have certain limitations and scope of application (Li, 2014, Durand, 1952, Wasp, 1977, Wilson, 2004, Wei, 2015). Among them, the classic Durand formula has been tested by years of construction experience (Ministry of Transport of the People's Republic of China, 2012), and it can basically predict the transportation resistance of common materials such as silt, silt and fine sand in large-diameter pipelines (such as DN750 and DN850). At the same time, some scholars have carried out a series of studies on the influence of different particle shapes on the transportation resistance of straight pipelines and vertical pipelines (Chung, 1998, Chen, 2020). In recent years, the filling medium in the expansion projects of Xiamen Airport and Hong Kong Airport is mainly medium and coarse sand. According to the situation of on-site construction, the pipeline transportation resistance is greater. However, the Durand formula in the dredging specification is mainly obtained through theoretical analysis and experimental data with small diameters, and cannot very accurately represent the characteristics of pipeline transportation under the conditions of large diameters, large flows and high concentrations. Therefore, it is not suitable for DN850-Q235 pipeline transportation of coarse sand, which brings difficulties to the friction size, row spacing and output of coarse sand in pre-side pipeline transportation.
Lin, Meihong (CCCC Fourth Harbor Engineering Institute Co., Ltd) | Su, Linwang (CCCC Fourth Harbor Engineering Institute Co., Ltd) | Ying, Zongquan (CCCC Fourth Harbor Engineering Institute Co., Ltd) | Wang, Xuegang (CCCC Fourth Harbor Engineering Institute Co., Ltd)
ABSTRACT A tension leg mooring system based on the three-dimensional potential flow and dynamic mooring theories is proposed to improve the hydrodynamic performance of a submerged platform. Frequency-domain and time-domain analyses are conducted using ANSYS AQWA while considering the shallow water effect, the draft of the submerged platform, and the mooring line and construction-related parameters. The response amplitude operators (RAOs) of the submerged platform are obtained. As the platform is submerged into the water, the heave and roll responses and their natural motion periods decrease, improving the wave stability and adaptability of the platform. The dynamic responses of the submerged platform during the working condition are analyzed, focusing on the motion of the platform at different locations. Time-domain simulations of the tension leg mooring system are conducted, considering the coupling effect of the heave and roll. The maximum heave values are obtained for different wind, wave, and current conditions to reduce the heave and roll motion of the platform. When the leveling machine is located at the corner of the platform, the limit conditions of the environmental parameters must be considered to meet the leveling accuracy requirements. Parameter optimization is conducted for the draft of the platform and the pretension force of the tension leg under different conditions to improve the leveling accuracy. The optimized mooring has a leveling accuracy of ± 40 mm. This study provides an approach to determine the parameters of the tension leg mooring system for the design of shallow water construction platforms for water transportation engineering. INTRODUCTION Immersed tunnel engineering is used in road construction to cross rivers and straits. It has been used since the beginning of the last century and is widely applied (Lunniss and Baber 2013). Due to the advantages of a shallow buried depth, low foundation requirements, and a short construction period, immersed tunnel design has been used by many developed countries globally. This technology has high design and construction requirements. The foundation is a crucial aspect of immersed tunnel construction because it affects the deformation stability during construction and operation. An increasing number of tunnels have been constructed using the pre-bedding method (Hu, Xie et al. 2015). This method was used in combination with a specially designed ship to install the foundations of the Busan-Geoje Link (Janssen, de Haas et al. 2006) and Hong Kong-Zhuhai-Macao Link (Hussain, Wong et al. 2011). Leveling ships are designed to reduce the impact of the wind, waves, and current on the leveling accuracy of the foundation and are used for three reasons: installing the pile legs, lifting the leveling structure above the water surface during construction, and reducing the impact of waves (Hu, Xie et al. 2015). The feeding structure and leveling structure are separated, and leveling is achieved by the underwater leveling equipment to reduce the influence of waves and improve the leveling accuracy. Leveling platforms with a semi-submersible hull are required to reduce the influence of waves.
Li, Gang (Engineering Company, Offshore Oil Engineering Co. Ltd) | He, Ning (Engineering Company, Offshore Oil Engineering Co. Ltd) | Fan, Yuyang (Engineering Company, Offshore Oil Engineering Co. Ltd) | Liu, Lixin (Engineering Company, Offshore Oil Engineering Co. Ltd) | Zhang, Rubin (Engineering Company, Offshore Oil Engineering Co. Ltd)
ABSTRACT The SSIVs were located on the pontoon of SEMI, which shall be towed to site offshore by wet-tow method, and which case was the first-of-its-kind in China. the SSIVs shall moving up and down near the sea surface, so all the SSIV related facilities would be exposed to severe environmental conditions. This paper presents the system design of SSIV, the protection method and shows the analysis process against the challenge mentioned above. This can provide a good reference to the similar projects INTRODUCTION Lingshui17-2 (hereinafter referred to as LS17-2) gas field is located in the northern part of the Qiongdongnan Basin in the western continental shelf of the northern South China Sea, with water depth of 1220m to 1560m. LS17-2 gas field is approximately 149km away from Sanya, Hainan Province, about 160km southeast from existing Yacheng 13-1 gas field, and about 90 km from gas export pipeline (YC13-1 to Hong Kong). The distance between LS17-2 gas field and the nearest onshore terminal (Nanshan terminal of YC13-1 gas field) is approximately 156km. The development of LS17-2 gas field consists of subsea production system, one SEMI and subsea pipelines. The subsea production system comprises one west manifold and three east manifolds. The SEMI platform is located near Manifold EAST1. Well fluid from west production loop will be transported to LS17-2 SEMI for process through two 10" pipelines and two 10" SCR risers. Well fluid from all east manifolds will converge at Manifold EAST1 and then be transported to LS17-2 SEMI for process through two 12" SCR risers. After processing, qualified natural gas shall be pressurized and transported to subsea pipelines from YC13-1 platform to Hong Kong through a 18" subsea export pipeline. Condensate oil shall be sent to the storage tank on LS17-2 SEMI and be exported by DP Shuttle oil tanker.
Amanda Tay is an analyst at Douglas-Westwood's Singapore office, focusing on the offshore sector, liquefied natural gas (LNG), and floating LNG. Before joining the company, she worked in finance, having spent several years in the investment banking and wealth management divisions at UBS and HSBC in Singapore and Hong Kong. Tay holds a bachelor of business degree in banking and finance from the Nanyang Business School of the Nanyang Technological University in Singapore.
Asia is the largest and the most populous continent in the world covering an area of 44,579,000 sq. Its 4.5 billion people form roughly 60% of the world's population. To understand the intricacies of this vast and diverse continent, it is a common practice to categorize the constituting countries as per the subject--economic development--under discussion. One such categorization is "Tiger Economies." It is the nickname given to the economies of Southeast Asia. The tigers are South Korea, Taiwan, Hong Kong, and Singapore.
Liuhua4-1 (LH4-1) oil field is located 215 km southeast of Hong Kong in the South China Sea. The field was first discovered in 1987, but because of economic and technical challenges, it was not until 2012 that the development of this field became a reality. The 300-m-water-depth oil field was successfully tied back to an existing oil field [Liuhua11-1 (LH11-1)] through subsea pipeline, power cable, and multiplex control umbilical. The project executions included disconnection, life extension, and reconnection to the existing oilfield floating-production system (FPS). It was also China's first tieback subsea development project.
To further reduce backpressure on low-pressure gas wells and increase reserves in a mature gas field, a gas-ejector project was evaluated and proposed. Following on-site tests on several gas wells, the gas ejector was put into service successfully. Reservoir simulation estimates that 6.4 Bcf of incremental reserves will be achieved through gas-ejector installation by decreasing inlet pressure to 50 from 100 psi. The application of the gas ejector during a 2-year period to reduce backpressure has helped to improve economics in a mature gas field. The YC13-1 gas field commenced sales from offshore platforms to Hong Kong and Hainan Island in 1996.
Cao, Hao (College of Water Conservancy and Hydropower Engineering, Hohai University) | Yuan, Saiyu (State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University) | Tang, Hongwu (State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University) | Lee, Joseph Hun-wei (The Hong Kong University of Science and Technology)
ABSTRACT In coastal waters, algal blooms (the rapid growth of microscopic phytoplankton) are often observed. The resulting oxygen depletion and even poisoning make local fisheries suffer severe damages. The dynamics of harmful algal blooms (HABs) are poorly understood. Novel models applying unstructured grids, e.g. Delft3D Flexible Mesh (Delft3D-FM), offer a good tool for a better representation of the hydrodynamics of coastal waters. In this paper, the performance of Delft3D-FM in hydrodynamic simulation of coastal waters was examined by a series of benchmark tests. At the end, the simulated tidal flushing processes in Hong Kong harbours were compared with previous studies. INTRODUCTION In subtropical coastal waters around Hong Kong of China, algal blooms are often observed. Harmful effects caused by algal blooms include dissolved oxygen depletion, fish kills, shellfish poisoning, and beach closures. In April 1998, a devastating red tide initiated in Mirs Bay resulted in the worst fish kill in Hong Kong's history - over 80% (3,400 tones) of fish stocks in HKSAR were wiped out, with an estimated loss of over HK$312 million. More recently, a severe algal bloom event started in Tolo Harbour in December 2015 and lasted for two months, resulting in fish kills and threats of spreading to outer Mirs Bay and Southern Waters. Despite significant upgrades of the water pollution control infrastructure over the past two decades, red tides and HABs still occur frequently in Hong Kong and present formidable challenges to fisheries management. The team is working on setting up an early warning system for HABs. As the core of the forecast and management system, the tidal circulation and transport of pollutants are determined by hydrodynamics. A 3-D hydrodynamic model using structured grids, i.e. Delft3D, has been applied and validated for Hong Kong waters before (Lee and Qu, 2004). To provide a better representation of the irregular coastlines including that of islands, an unstructured-grid model (Delft3D-FM) is attempted to be adopted. In this paper, the performance of Delft3D-FM in hydrodynamic simulation of coastal waters was examined by a series of benchmark tests. The computational results were compared with analytical solutions or laboratory findings. At the end, the simulated tidal flushing processes in Hong Kong harbours were compared with previous studies using Delft3D.
Zhang, Jiaying (CCCC Tianjin Port Engineering Institute Co., Ltd. of CCCC First Harbor Engineering Co., Ltd., Key Laboratory of Port Geotechnical Engineering of Ministry of Communication, Key Laboratory of Geotechnical Engineering of Tianjin / CCCC First Harbor Engineering Company Ltd.)
ABSTRACT At present, there is no ripe experience of settlement characteristics and calculation of soft foundation in offshore immersed tube tunnel. In this paper, rebound and recompression modulus of the natural foundation of immersed tube tunnel are studied by laboratory consolidation and rebound test. The law of soil rebound and recompression deformation changing with loading is revealed. INTRODUCTION With the rapid development of port engineering and construction technology, the immersed tube tunnel will become the main way of cross-river and cross-sea project. To ensure the construction quality and operation safety of immersed tube tunnel, the requirements of installation precision and settlement control are very strict. Normally, the tunnel is placed in the excavated foundation trench, then, the trench is backfilled and the tunnel is locked. The foundation soil experiences the process of unloading and reloading. Therefore, the accurate calculation and characteristic analysis of rebound and recompression settlement of tunnel foundation are very important to ensure the safety of immersed tube tunnel. In recent years, many scholars have carried out research on the resilience of foundation excavation. Duncun (1970) carried out the finite element calculation of foundation heave by using the curve model. S.K.Bose.N.N.Som (1998) used two-dimensional finite element method to simulate excavation process by steps of foundation and the change of support mode. Pan Linyou and Hu Zhongxiong (2002) put forward the concept about the range of rebound area and strong rebound area. Li Jianmin and Teng Yanjing (2010) proposed the concepts of reloading ratio and recompression ratio through the rebound and recompression test and model test of a large number of soil. And they also obtained the basic law of soil recompression deformation. Xv Gancheng and Li Yongsheng (1995) calculated the rebound deformation caused by excavation with different formulas. Although the above scholars have carried out the systematic study on the soil rebound and recompression problem, however, there are few studies on the rebound and recompression of immersed tube tunnel foundation soil under special working conditions. Because of the regional difference of foundation soil, this paper is based on the immersed tube tunnel foundation of the Hong Kong-Zhuhai-Macao bridge. And the study on deformation characteristics and law of soil rebound and recompression are carried out.
Wei-guo, Duan (Weinan Normal University) | Zi-shang, Li (Northwestern Polytechnical University) | Jie-qiong, Zhang (Northwestern Polytechnical University) | Zi-hao, Yang (Northwestern Polytechnical University / CCCC Submerged Floating Tunnel Technical Joint Research Team) | Wei, Lin (CCCC Submerged Floating Tunnel Technical Joint Research Team / CCCC Highway Consultants Co. Ltd.)
ABSTRACT Deflection of the tube of submerged floating tunnel (SFT) under environmental loading such as current, long crest wave or even sea density variation as well as its vibration characteristic are of great interest to engineering researchers. In this paper, the simplified two-dimensional SFT mathematical models are expressed by a set of partial differential equations, including four partial differential equations and four boundary conditions, totally 16 combinations. Each represents a type of SFT with a specific way by which the tube connects to the shores. They are SFT with or without cables, SFT with or without axial compression or tension, SFT with two fixed or pinned ends and SFT with only one pinned or fixed end. And the last one stands for the constructional stage. The analytical solutions to the simplified two-dimensional SFT models are obtained by using the method of variables separation. And these solutions apply to the tether type SFT in both operational stage and constructional stage, where the cable mass must be negligibly small compared to the tube mass, tube section must be constant along its length and the cable is idealized by continuous springs. Finally, the examples of application are given. The research results provide a theoretical reference for further study and construction of the SFT. INTRODUCTION The SFT was proposed more than 150 years ago. Norway, Turkey, Italy, Japan and China have all studied it at different times, but it has never been built . The Hong Kong-Zhuhai-Macau bridge islandtunnel project has built the longest highway immersed tube tunnel in the world, overcoming a series of difficult problems such as the installation of complex sea conditions, deep burial, siltation, abnormal waves and plume. Today, immersed tube tunnel technology has been developed into the third generation, and the next breakthrough should be the realization of SFT technology . After the completion of the Hong Kong-Zhuhai-Macau bridge island-tunnel project in 2018, China Communications Construction Company Limited has set up the Joint research group of suspended Tunnel Engineering Technology with 11 research directions , and the model of education, research and production has also been established. Participating organizations include Northwestern Polytechnical University, Dalian University of Technology, Dutch TEC company, Delft University of Technology, etc. The research team of structure and design method was established in 2019. And this paper is one of the research achievements of the project team.