Analysis Of The Stability Of Structure Foundation And Adjacent Seabed In Chengdao Shallow Sea Area

To get the stability of shallow structure foundation and adjacent seabed in Cheng Dao shallow sea area, we have made an investigation on high resolution echo depth side sonar and shallow strata section etc. and made use of experiment Analysis of core , in situ , indoor to compute , analyze and assess the stability on new computing method. We have got factor values which influence directly safety and stability, including structure and around wash load structure foundation sink value and liquefaction depth, and we discuss underlying bed response in different marine environment parameters. The paper do also consider the influence of structure to around underlying bed evolvement and couple relation of instability damage phenomenon on bottom and structure.Through analysis, we conclude that washing action of wave and flow is main power of evolvement of region of interest landform, structure lead to the fact that water area around shallow structure in Cheng Dao sea field has an increase about 0.3m/a through actual measurement, water depth increase rate around foundation is 0.25m/a, slope gradient of side slope averagely has a decrease of 5%o a year, however marine hydropower wash rate through compute is 0.2m/a on underwater bottom, the wash rate on structure foundation is 0.35m/a. Except hydropower wash, another important cause of the difference is that shallow stratum soil mass bulk movement make local shallow surface sediment fill deep water bottomland, so slow up the deep rate of deep water bottomland. This kind of instability bulk movement is induced by wave cyclic loading, as a result the slope of bottom bed decrease, water depth increase, and instability bulk movement has the character of subregion, regularity and head erosion, thus it will influence evolvement of region of interest landform, and change flow field and bottom stratum condition continually, so will lead to dynamic influence on structure foundation soil.Through analyzing bed's response to wave, in the condition that super-stratum ismore hard and second-stratum is more soft in region of interest, super static interstitial hydraulic pressure amplitude die away rapidly between stratums, before in sight of boundary between hard and soft stratum, plane effective pressure increase to max. Shear stress reach peak value when bed thickness is approximately 2.7 meters, then it will decrease to the minimum on the place where the flexible soil has a common boundary with the rigidity, so the boundary is the most destroy plane on engineering. On the basis of reconnaissance in situ, In normal situation of sea, the structure slides to the basin along the boundary. In the storm, the part on surface layer of the underlying bed will produce the liquefaction, the absolute standing wave that form the front of the structure may bring 6.16 meter depth of the liquefaction, so the foundation of structure will lose part of the supporting force ,the structure will slide in this situation. That is to say, because of the foundation partly liquefaction, the exist of soft layer and the component force of gravity, the structure slide further to the basin and collapse, which leads to disastrous consequence.By calculating instability factor in research area, this paper gives some corresponding suggestion. This paper shows engineering instability around instrument foundation and coupling relation to the circumjacent seabed, and research the dynamic response between wave and seabed, and enriches the research content of instability of seabed around instrument foundation and give some appropriate suggestion to foundation planning of ocean engineering, also it prevents instrument , facility and property of state from losing and risking.