Research On Engineering Geological Environment And Its Suitability In Chengdao Sea Area

Chengdao sea area is located in northen shallow sea area of the Yellow Riverdelta.The Yellow River migrated north and flew into the Bo river through ShandongProvince in1885and formed eight lobe delta in estuary in one hundred years. Thestudy area is above (1953-1976) two-period lobe underwater delta. The Yellow Riverchanged its direction to Qingshui channel in1976, the sedimentary environment ofChengdao sea area changed significantly. Depositional pattern changed intoerosion.Under the effect of the ocean current,wave and so on,the micro-geomorphicwidely developed in the sea area and shallow strata engineering geological conditionsare complexed.The depth of water of the study area is from1to20meters. The seabed of mostwells is mainly smooth submarine geomorphy.10years’ geological exploration datashow that the surface sedimentary patterns of Chengdao sea area is silt,silt clay,verysoft silty clay and ooze.and so on.The surface sediments is mostly silt and silty claywhich is consisted of the underwater sand body of Yellow River delta and neriticsediment since holocene ‘s transgression. The physical indices of surface sedimentlike moisture content,void ratio and plastic index and so on grow large from the bankto the sea and their variation trend is similar. The mechanical indices likecompressibility coefficient,SPT N values, shear strength and so on show the sandbody of estuary has good engineering properties.Accorrding to the depth of water,geographic and geomorphic conditions,stratadistribution characteristics and engineering geological properties.the thesis divides thestudy area into four zones.The geography ofⅠzone is smooth, silt is main the surface sediments.There arehigh strength silt layer in20meters deep strata. The geological disaster factors isless.it’s stable waters.There are relatively light discrepancy in elevation groove orlong gang in Ⅱzone, the nature of surface sediments has large differences.It’s stablerstate waters. The geography of Ⅲ zone is bumpiness,sizzling sand is main the surfacesediments under which is weak silt clay.The geological disaster factors oflandside,rift and so on is more.it’s unstable waters. The geography of Ⅳ zone is flat, soft silty clay is main the surface sediments.The Geological disaster factors is less.it’spedrocratic waters.Seat bottom type platform is suitable for working in Ⅰ zone,the depth of water,geographic and geomorphic conditions should be considered when working in Ⅱ andⅢ zone.The depth of water of Ⅳ zone is deeper than others.So it’s not suitable forworking. Big pile boots platform is suiable for working in Ⅰ zone、 Ⅱ zone andⅣzone.When drilling platform constructs in Ⅲ zone, the soil layer must be ensured thatit can’t be impated. Deep pile platform is suitable in every zone.20-30meters deepcan be as bearing stratum.Geographic and geomorphic,wave and tide is the main the factor that influencingthe project of the leg of platform is washed.Before the Ocean Engineeringconstruction,we should know the rule and trend and take actions to avoid the marineengineering geological disasters...