Applied Mechanics and Materials Vols. 256-259

Abstract: The observation wave induced setup can be separated from observed total water level which combines tide level, weather induced setup and wave induced setup. SandyDuck ’97 experiment provides lots of observation data. Separation of tide level form preliminary data is using the nearest tide station’s predicted tide. The weather induced setup is given by numerical model which includes the effects of air pressure and wind blows. The residual water level, wave induced setup, seems reasonable and available, and the time series trend match with wave high trend at same location.

Abstract: In order to study the working characteristics of high-pile wharf pile foundation under berthing load, our team conducted the field test and established the numerical models. Analyzing the data from the test and models, the relationship between load and displacement of piles was deduced primarily. It’s proven to be usability.

Abstract: The far-flung ocean has abundant resource and the exploitation area of ocean oil and gas is developing from offshore to deepwater and ultra-deepwater following the increase demand for oil and gas resource. Therefore, one of the floating structures for deepwater exploitation is FPSO. The yaw of FPSO is more important problem to solve. This paper use Hydrostar to compute the RAOs, 1st-order and 2nd-order force of FPSO. A comprehensive review is introduced about the research on FPSO hydrodynamic in the world, including the coupling hydrodynamic analysis of deepwater FPSO with the mooring system. The results indicate that the FPSO’s 1st-order force and moment is a little large, however, the RAOs and 2nd-order force and moment are good. The FPSO with single point mooring system can control the displacement of FPSO effectively.

Abstract: Jetting power has been applied more and more frequently to create trench in the seabed to bury cables or pipelines under a protective layer of sand in offshore engineering. However, there are still several key problems to be understood further and solved both in their design and operating. This study investigates the topographic deformation due to the scour of silt beds which lie below marine pipelines and are impinged by moving two jets in a model experimental system. The response of silty sea beds was also examined during the experiment. The important parameter that influences the trenching performance, the jet velocity, was studied. The speed of the jet horizontal motion was varied to examine its effect on the scour profile. By presenting the variation of a scour profile with time after impingement, the change process was analyzed. The asymptotic scour profiles were found to be very similar when made non-dimensional, and a function was employed to describe the non-dimensional profile. The results of the above work will permit a better understanding of the mechanisms controlling the performances of underwater trenching by jet trenching machines.

Abstract: In order to study the specialties of wave slamming on open-piled structures, a two-dimensional regular wave tank was established based on commercial CFD software FLUENT. Three typical cases of regular wave slamming on the open-piled structures were reproduced by using the numerical wave tank and compared with the experimental data available. Good agreements were obtained between the numerical and experimental results and the average of peak impact pressure was chosen as the characteristic impact pressure. Then regular wave impact pressure on the open-piled structures under various wave height, period and over height were simulated. The influences of the three parameters on the distribution of impact pressure were analyzed.

Abstract: Harbors or seaports are major hub of human economic activities, and also centers of environmental issues, which have environmental impacts on the estuary, tidal marshes and coastal wetlands. This paper analyzed the impact of transportation construction on coastal area, reviewed the ecological restoration techniques for habitat under transportation construction, proposed the procedure of suitability analysis of ecological restoration and established an evaluation criteria framework of ecological restoration suitability. The suitability framework which is set up by using Analytic Hierarchy Process (AHP) in this paper could be applied to analyze suitability for ecological restoration of transportation construction projects.

Abstract: At present it is difficult to thoroughly clear away the marine oil-spill when collision takes place. As we know the traditional oil-spill-treatment is slow and the oil pollution can not be handled timely. In order to clear the surface oil and protect marine environment, a study on rapid- clearing of marine oil pollution system is presented in this paper, which is equipped with a high-resolution camera on the top of the oil pollution lifter to identify the oil pollution and get data by image processing, then the oil pollution recovering which is set in the front of the oil storage tanks collecting oil spill by the single-chip machine while moving. Thus the oil spill can be separated into clean oil and water by the oily-water separator through the flexible tube. This system is more efficient, cleaner and less-polluted than the traditional one, which is worthy of large area surface oil-spill clearing.

Abstract: According to the reef blasting environment characteristics and shape charge blasting construction technology requirement, we design a set of electric detonator - detonating cord - unconductance detonation tube detonator network. Introducing the engineering application of three kinds of network connection mode, the craft is simple, the operation is convenient, safe and reliable. It has reference and application value in the similar engineering.

Abstract: This paper aimed to research the effects of inertial mass coefficient on knotless netting models used in tuna purse seine. Knotless nettings were modeled and simulated using mathematical and mechanical models. In the simulation, the marine environment was imitated in the computer. The results demonstrated that inertial mass coefficient was a key factor to affect the stability of knotless model, especially in the sinking process, and the model presented more stable and quicker convergent as the inertial mass coefficient increased. During fishing operation at sea, the instability of the sinking of purse seine with knotless nettings, especially in the area with complicated currents and waves, might be due to the smaller inertial mass coefficient of knotless nettings.

Abstract: As a new type of deep water offshore foundation, suction caisson is widely used to offshore structures. However, the current methods of evaluation and design cannot meet the increasing requirement of engineering practice. In this dissertation, the studies are emphasized on finite element method for analyzing the suction caisson bearing capacity behavior and the failure mechanism under the vertical load. Based on studying the vertical bearing behavior of caissons with different ratio of length to diameter L / D, it shown that as L / D increases, the vertical bearing capacity growth slowed.