Response Of Natural Geological Environment To Man-made Structures Into Chengdao Sea Area

In order to understand the response of natural geological environment to marine structure into Chengdao sea area, this paper is combining the survey data of side-scan sonar, sub-bottom profiler, the single-beam sounder and etc, same with a large number data of well site and experimentation. In recent decades, coastline was been eroded by waves more and more, and it is a big security threat to marine engineering facilities. understanding of the relationship between artificials and natural the geologierocal, studying the response of coastline or near sea to artificial structures, are important practical significance for studying the effect of oil drilling platforms, subsea pipelines, cables and other artificial structures to coastal erosion, as well as corrosion protection of oil facilities.Under the natural geological environment in Chengdao area, the water depth will be increased gradually, the evolution law is from the status of rapid erosion, to washed into the slow phase, final dynamic equilibrium. The main geological changes form of the impact of sea bottom topography in Chengdao, have the abandoned delta of the erosion and geological instability of the seabed. geological The instability of Seabed has embodied in the ways of collapse pits for the seabed, sediment and debris flow landslides and collapsed partially.With the development of Shengli Oil, it have constructed a large number of artificial structures, such as oil platforms, undersea oil pipelines, submarine cables and others, including oil platforms which of some of the piles have very strong impact of natural geological to environmental. The result of analysis show that the construction of oil platforms will affect the surrounding seabed topography, breaking the original hydrodynamic conditions of the environment, causing the second vortex in the waves and the deepest of scour is up to 2.2m, which is under the combined effect of the trend on the seabed. At the same time, there are a large number of unstable landforms around platforms, such as: low-lying land erosion, convex. The pipelines will also impact on the seabed topography. Through the analysis of the mechanism of pipeline erosion, and the depth data measured in different years and the multi-beam images, sub-bottom profiler images, it show that the pipeline have important effect on its terrain, and pipelines are not only change its original surrounding topography and soil characteristics, but also make more intense of the hydrodynamic conditions, finally resulting the erosion of the seabed topography and the largest erosion may up to 0.3m, and there are unstable landforms such collapse pit near pipeline.The influence of manmade buildings to seabed is no longer a small-local but is regional. On the other way, natural geological environment is also affecting the engineering facilities. There is a mutual relationship between each other. The lots of artificial structures increasing the effect to the seabed, so that the contour map of the depth of water is clearly convex the side of the land. Another, the seabed material which had eroded, is filling sediment around the structures and forming a shallow by the circular action of tide wave. So it clear that the contour map of the depth of water near here is clearly convex side of the sea, which have a great practical significance to the protection of cables and other submarine pipeline routing facilities.In this paper, there is only a qualitative analysis of the feedback effect which the geological environment to the artificial structure, there is lack of quantitative in-depth study of the numerical calculation that the influence which artificial structures on the natural geological environment, and have not a model that quantitative calculate changes the contour map of the depth of water in Chengdao waters.