Studies On The Offshore Artifical Island Stability Basing On AHP-Fussy ERvaluation Method

The Laizhou Bay is an important shallow water oil and gas region, with the development of marine resources and spaces and the constructions of offshore engineerings, it's necessery to get a comprehensive understanding of the engineering geological environment in the western Laizhou Bay.Based on the measured data and experimental data, the paper systemly analysed the engineering geological environment which contents the crust stability, seabed stability, foundation stability, and marine environment. The results of this study are as follows:Characteristics of regional crustal stability: the crusal stability of the engineering is substable according to the activities of the faults and earthquake and the land subsidence.Shallow strata: mainly silt and silty clay. the top floor is silt and silty clay interbedded stratum, and extremely unstable; upper silt floor is the Yellow River deltatic deposits, with low density ,high water content, high compressibility, where there are obvious weak layers; the lower floor is a fluvial and lacustrine sedimentary stratum with high density, this is a good engineering bearing layer. The upper silt floor is not easy landslide, but is easy liquefation, the liquefaction risk of the improved foundation exists; the engineering soft stratum has a fine bearing capacity, impacting little on the engineering.In general, tidal affects little on the artificial island, it needs a long time for the seabed to reach a equilibrium, the biggest erosion can reach 3m; normal waves affect little on the artificial island, too; storm surges affect on the artificial island much, the balanced seabed can be eroded 3m or so by a storm surge action. So it should pay special attention to bottom protection projects.The stability evaluation of the artificial island is based on regional engineering geology and sets geological disasters as objects, according to engineering geological environment characteristics of the west Laizhou Bay, Using the fuzzy comprehensive evaluation method, the stability of engineering geological environment of an artificial island was evaluated, and an evaluation system for assessing the stability of artificial islands was established. Thirteen influential factors were selected as the evaluation index, which were classified into four categories, i.e.: regional crustal stability (including geologic structure features, seismic intensity, and ground subsidence), seabed stability (including topography, liquefaction, and scouring), foundation stability (including bearing stratum, engineering soft stratum, and buried ancient channel), and marine environment stability (including storm surges, tidal current, wave height, and water depth). The AHP method was used to weigh those factors. The research results would be helpful to the construction and safety estimation of artificial islands...