The Analysis Of Engineering Geological Environment And Particle Size Indication In The Northern Chengdao Sea Area Of Yellow River Delta

Chengdao offshore sea area of oil and gas development engineering project islocated in the northeast of the compound delta of the Yellow River which is directlyimpacted by eastward strong waves in the Bohai sea.Since the Yellow River diversionin1976, the sea river sediment input was directly cut off.Coast and the underwaterbank slope were severely erosion, and offshore oil production areas located in this seaarea is basically in a state of strongly scouring and erosion.Tides is complex, and tidalcurrent effect is strong. The storm surge is of frequent occurence, while thehydrodynamic effect is strong.The combination of these factors makes the characteristics of this sea seacondition, shallow geological conditions and deformation of soft sediments are verycomplex, and it is prone to a variety of disasters and geological phenomenon. It makesocean engineering environment of the offshore pipeline changed more easily. Changesin ocean engineering environment make the submarine pipeline in a strong corrosiveenvironment easily and cause the submarine pipeline failure in the study area.Therefore, systematic, scientific research on the effects of marine sedimentaryenvironment change to the engineering geological conditions, becomes a necessary.Data in this paper based on the Shengli Marine environmental geology surveyassessment project of chengdao oil field. We analys and process to obtain the waterdepth and granularity parameter data as well as engineering geological parameters, byMarine survey sampling, in situ test and laboratory experiments.In this paper, we obtain the the statistical correlation of geological environmentand the grain size characteristics curve of the relationship between the variousgeological parameters and particle size parameters, and then linear regression fittingand get further research on the engineering geological characteristics of the grain size characteristics of indicative based on the statistical correlation analysis of the study ofthe plane distribution characteristics of surface sediment’s salinity, pH, Eh, and theparameters of the physical and mechanical properties such as density, moisturecontent, water depth, grain size parameters as well as the the vertical distributioncharacteristics of physical and mechanics parameters of each foundation soil layer ofthe study area in central drilling hole.Analysis results show that for the surface sediment, Its distribution characteristicsmainly controlled by water depth and distribution of Engineering geologicalenvironment index and grain size parameters in the study area has zonality. sedimentin the west and southwest have high pH, Eh, density, salinity, low moisture content,high average particle size distribution, median diameter, skewness, kurtosis value,small sorting coefficient. The sediment is coarse, and sediment fraction is relativelyconcentrated. Sediment is given priority to sandy silt and silty sand.East and northeastsediment have low pH, Eh, density, high salinity, moisture content and small averageparticle size distribution, median diameter, skewness, kurtosis value. Sediment is fine,and sediment graded distribution is wide, mainly composed by silty and clayey silt.According to the surface sediment migration trending, and combined with correlationcan be concluded that from the coast to the outside, the deeper the depth of the sea, Eh,density of the sediments is smaller, and the pH, salinity and the moisture content isgreater when the depth is shallower than the fluvial equilibrium zone as well as the Eh,density of the sediments is greater, and the pH, salinity and the moisture content issmaller when the depth is deeper than the fluvial equilibrium zone.For the drilling sediment of Chengdao platform of number one sea area in thecenter of study area, there is a certain correlation physical and mechanical propertiesparameters of soil such as water content, dry density, wet density, density, saturation,porosity ratio, liquid limit, plastic limit, plasticity index, liquidity index, coefficient ofcompression, compression modulus, cohesion, friction angle and particle sizeparameters such as average grain size,median grain size, sorting coefficient, skewness,kurtosis, as well as the sampling depth. On this basis, the engineering geologicalconditions formed by sedimentary environments of each geological period can be evaluated. And the evaluation results are basically in accord with the experimentaldata.Therefore, the grain size characteristics of sediments have good indicative andcan be assumed to be a experience method to evaluate soil physical parameters of theengineering geology for drilling sediment of number one center platform in chengdaosea area.In this paper, our study enriched the content of the submarine engineeringgeologic environment research, and provide theoretical basis for the analysis ofengineering geological environment in the study area. It has certain actual applicationvalue to the topic for the submarine pipeline laying in the study area and theconstruction of ocean engineering.