The Study Of Gravity Anchor System Used In Deep-water Buoy

With economic development of the world,many countries have begun to develop and quest the ocean.In the wide ocean,the quantities of the ocean engineering structure are increasing.The developments of the ocean have already steered for 40-50 years,the ocean engineering develops from near shore to deep and far ocean.In order to measure and collect the data of the ocean environment,the use of the buoy is being confirmed.In the marine buoy system,the mooring system is an important part of it,especially in the deep-sea.The configuration and structure of the buoy anchor system are the key parts to ensure the normal working of the buoy and are the main factors restricting the depth of the ocean development.Marine observation buoys need to measure subsections within a certain range.To reach a certain depth and depth requirements,the mooring system needs a reasonable configuration and at the same time can maintain this design configuration when deployed.To achieve this requirement,the actual depth of the anchor site and design depth can not be too much deviation.In order to overcome this problem in the traditional deep-sea buoys deployment,two types of releasable gravity anchor systems for deep-sea buoys are proposed in this paper,and the schemes are compared.In order to achieve the above goal,this thesis has carried on the following work:(1)Mooring system and anchorage foundation stress analysis.The environmental load on the mooring system is analyzed,including the calculation method of wind load,wave load,flow load and so on.Using iterative method to write MATLAB program to calculate the mooring system tension.(2)Design of releasable gravity anchor system.Based on the calculated environmental loading of the anchoring foundation,two types of releasable gravity anchor system solutions for buoys are provided.The first underwater gravitation with gravity anchor opens the rupture bolt,releasing the chain from the chain box.The second use of gravity anchor underwater weight start servo pressure cylinder,trigger chain control system,release the chain in the chain box.(3)Study on horizontal bearing capacity of gravity anchor.The horizontal bearing characteristics of gravitational anchor on clay were studied by indoor model test.The horizontal bearing characteristics of flat-gravitation anchor and eight-key gravitational anchor under different strength of soil were obtained.The gravity anchor system was simulated by ABAQUS finite element numerical software to investigate the bearing capacity of the gravity anchor of this design and to further optimize the design of the anchorage foundation.Through the indoor model test of gravity anchor and the finite element analysis of the system,the following conclusions are drawn:(1)According to the characteristics and special needs of deep-sea buoys,this paper presents a structure of gravity anchor system that can release anchor chain.It consists of a chain box and a gravity anchor.When the actual depth of water buoy is greater than the designed gravity under the condition that the anchor can not reach the sea floor,the anchor chain in the chain box can be automatically released so that the gravitational anchor reaches the sea floor,and the bearing capacity of the superstructure is provided.(2)The form of gravity anchor proposed in this paper is influenced by its structure and shows different horizontal bearing characteristics in different states.When the anchor chain is not released,it is equivalent to the string anchor state.The anchor box and the gravity anchor simultaneously provide the horizontal bearing capacity and the bottom soil body is raised.When the anchor chain is released,the chain box loses most of the weight and is mainly provided by the gravity anchor Bearing capacity,gravity anchor below the soil deformation.(3)When the anchor chain is not released,the chain box and the gravity anchor form a string anchor.When the length of the anchor chain changes,the bearing capacity of the system will be affected.When the chain length increases from 0.2m to 0.5m,the horizontal bearing capacity increases largely but remains unchanged.When the length of the anchor chain increases from 0.5m to 1m,the horizontal bearing capacity decreases slightly but remains unchanged.When the anchor chain increases from 1m and 3m to 10 m,the horizontal bearing capacity shows a downward trend and then increases basically and remains unchanged.