港航外文翻譯-使用普林斯德 nederlanden 耙吸挖泥船降低“阿西歐元林克”號沉船的高程（原文）

1、Deepening the wreck of the Assi Euro Link by using the Trailing Suction Hopper Dredger Prins der Nederlanden B. Jacobs1 Abstract: In January 2003 the freight ship Assi Euro Link sank after a collision, 48 nm off the nor

2、th coast of the Netherlands. As the wreck was located in a busy shipping lane it had to be either removed or lowered below the guaranteed navigable depth of 29 m. After taking cost and feasibility into consideration Ri

3、jkswaterstaat (Dutch Maritime Authorities) decided to have the Assi Euro Link lowered by dredging the existing sea bottom material around the wreck. During the second half of 2003 Rijkswaterstaat and Boskalis developed

4、 the dredging option. The combination of site conditions made the operation a dredging challenge, since it had never been executed before under these conditions. First the location of the wreck was unfavorable for worki

5、ng conditions, due to the open sea environment, very busy shipping and the depth of the sea bottom, which was almost 45 m. These conditions lead to the choice of a modern, versatile and highly manoeuverable trailing su

6、ction hopper dredger, being able to dredge up to 80 m. Second the soil properties played an important role, since the material had to flow from underneath the Assi Euro Link after dredging a hole around the wreck’s hul

7、l. Third the Assi Euro Link had broken up into two parts and some sections had even collapsed. The risk of damaging or even losing the suction pipe, by uncontrolled movements of wreckage was high. To ensure a safe op

8、eration a monitoring system with motion sensors was installed on the wreck, which registered sudden movements and gave a warning. Since the goal of the project was to lower the wreck below the required navigable de

9、pth an effort has been made to continuously monitor the exact location by using an Ultra Short Baseline (USBL) system. As a part of the system several acoustic sensors were fitted on the wreck, prior to dredging operat

10、ions. Keywords: wreck, deepening, dredging 1 Dredging Department, Royal Boskalis Westminster, Rosmolenweg 20, P.O. Box 43, 3350 AA Papendrecht, The Netherlands, E-mail: B.Jacobs@boskalis.nl 7 m Medium to coarse, ver

11、y dense sand Pleistocene (Eem & Molengat Formation) Hard clay Pleistocene (Clever Bank Formation) The results from the soil investigation provided sufficient information to answer questions concerning: ? Dredgebi

12、lity of the material with existing dredging equipment. ? Slope development of the material underneath the wreck. ? Possible excavation depth to create the required buffer to sufficiently sink the wreck parts. 3

13、EQUIPMENT CHOICE After studying the boundary conditions it was decided to use the brand new 16,000 m3 trailing suction hopper dredger “Prins der Nederlanden”, because of the advantageous characteristics for the executio

14、n of the project: ? Sufficient depth range. The vessel is equipped with one standard suction pipe layout, being able to dredge up to 55 m depth and one deep dredging layout for a working depth of 83 m. Furthermore the

15、 deep dredging layout contains an underwater pump, giving more flexibility and a higher production output when working in water depths of more than 30 m. ? A lot of installed jet power (up to 3,000 kW). As the Pleisto

16、cene sand layer was considered to be very densely packed it was foreseen that the slope development needed to be activated by means of jetting. ? Good manoeuvrability characteristics, making the vessel most suitable

17、for working in a restricted area and anticipate on possible ship traffic passing the site. ? Being able to operate at wave heights up to 3 m., which was considered a very important issue when working in April on the

18、North Sea in offshore conditions. ? Equipped with dynamic positioning (DP) and dynamic tracking (DT), giving the possibility to work very accurately. ? The vessel being self propelled and therefore suitable to evenl

19、y spread its load over the sea bottom at any given distance, without being an obstacle in the shipping lane. 4 RISKS From all the available soil information it was concluded that the Pleistocene sand layer was strongly

20、 over- consolidated due to an ancient glacial ice cover. Slopes in the excavated trench were expected to remain steep due to the soil behaviour, which would prevent the sand flowing from underneath the wreck in a natura

21、l way. Calculations showed that at least a hole of 10 m would be necessary to create sufficient slope development to have the wreck sliding on its own weight into the dredged trench. At approximately 10 m however there

22、 was the risk of encountering a hard clay of the Cleaver Formation, which was expected to have a negative effect on the formation of a slip circle, thus preventing sufficient slope development. To overcome the high soi

23、l risks, a special jetting device was developed to activate the slope development by jet water force. For this purpose, the jet consisted of two side nozzles and a nozzle directed backward. The device could be mounted

24、on the suction tube of the trailing suction hopper dredger and a total power of 5,500 kW was available (from one dredge pump and three jet pumps). A second option to create sufficient instability of the sand layer und

25、erneath the wreck was to dredge a second trench on the opposite side. Large pieces of debris, possible scattered around the wreck on the sea bottom causing damage on the suction pipe could stagnate the whole operation

26、. Therefore special focus was made on locating these pieces. This was done by ROV inspection, before the dredging operations started and during the start of the project by so called reconnaissance dredging. Reconnaissa

27、nce dredging contained pre dredging by covering the complete area around the wreck with one pipe, using the standard pipe line lay-out. Since this lay-out would not be used during the remaining dredging operations, dam

28、age on the pipe or draghead would not jeopardize the project planning. Knowing the exact position and monitoring the behaviour of the wreck during the operation was considered essential, as one of the objectives wa