摘要:
对渤海湾北岸晚第四纪沉积物进行详细的沉积学、年代学和物理力学性质分析研究发现,渤海湾北岸50 m以浅自上而下分为九个单元,依次为第一海相层、滨海湖、末次冰消期湖沼、末次冰消期初期沼泽、盛冰期硬粘土、河床、第二海相层、末次冰期间冰阶湖沼和末次冰期泛滥堆积。自然压缩固结引发的地面沉降与沉积物的含水率、孔隙比、黏聚力和压缩系数等物理力学性质关系密切。第一海相层的各项指数均较高,其次为第二海相层和末次冰消期的泛滥沉积,最小为盛冰期的硬粘土和末次冰期泛滥沉积。以孔隙比和压缩系数为指标,假设第一海相层压缩固结到沉积环境相似的第二海相层,需要压缩固结196.2 cm;末次冰消期泛滥沉积压缩固结到沉积环境相似的末次冰期泛滥沉积,需要压缩固结114 cm。30 m以浅地层的自然固结压缩速率最大为0.04 mm/a,远远小于目前的地面沉降速率。
Abstract:
s:Based on the detail analysis of the sedimentology, chronology and physical and mechanical parame-ters of the Late Quaternary sediments,we find that above 50 m in the northern coast of the Bohai bay, there are 9 units from top to bottom, corresponding respectively to the first marine bed, littoral lacustrine facies, last deglacia-tion limnetic facies, last deglaciation swamp facies, last glacial maximum hard clay, channel facies, the second marine bed, interstage of the last glaciation limnetic facies and the last glaciation overflow facies. Land subsid-ence caused by the compression and consolidation of sediment under natural conditions is closely related to the physical and mechanical parameters such as water content, void ratio, cohesive force and compression factor. These indexes reach maximum in the first marine bed, followed by the second marine bed and the last deglacia-tion overflow sediments, the last glacial maximum hard clay and the last glaciation overflow sediments. Based on the void ratio and compression coefficient, two strata with similar sedimentary environment are contrastive analy-sis. Supposed that the first marine bed do compress to the second marine bed, the length of compression in the first marine bed will reach 196.2 cm. Similarly supposed that the last deglaciation overflow sediments do com-press to the last glaciation overflow sediments, the length of compression in the last deglaciation overflow sedi-ments will reach 114 cm. The rate of natural compression of the layers above 30 m is 0.04 mm/a, much smaller than the present rate of land subsidence.
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