南黄海中西部海底空间沉积特征及工程地质特性

SPATIAL CHARACTERISTICS AND GEOTECHNICAL PROPERTIES OF SEAFLOOR SEDIMENT IN WEST-CENTRAL AREA OF SOUTHERN YELLOW SEA

南黄海海区被认为是我国在海上进行公益性、战略性油气资源评价的有利海区,但目前该海区海底深度方向上沉积特征及工程地质特性的研究仍较少。本文利用2009年6月及2010年6月在南黄海中西部海底获取的287个站位的沉积物柱状样品,通过粒度分析、物理力学性质测试,得到了该海域海底的空间沉积特征及沉积物工程地质特性:研究区海底表层沉积物类型多样,西南海底以粉砂质砂、砂质粉砂为主,力学强度较高,不易压缩,但由于较强的水动力条件,易冲刷粗化;东北海底以粉砂质黏土、黏土质粉砂为主,力学强度低,极易压缩;研究区海底深度方向上沉积物类型并非单一,常由几种类型沉积物互层组成,沉积物基本物理性质和力学性质随埋深变化的情况主要与沉积物类型有关,其次是压实作用。一定程度上,可利用本文给出的拟合函数,通过压缩波速估算研究区海底沉积物的孔隙度。

The Southern Yellow Sea is identified as advantaged sea area for evaluation of nonprofit and strategic offshore oil and gas resources in China. Currently,the study on the sedimentary characteristics and geotechnical properties in the depth direction of seafloor sediment in the sea area is sparse. By measuring and analyzing the particle size and physical-mechanical properties of the sediment cores collected from 287 stations in June 2009 and June 2010,we obtain the spatial characteristics and geotechnical properties of seafloor sediment in the west-central area of southern Yellow Sea. Investigation indicates that the types of surficial seafloor sediment in the study area are very diverse. The surficial seafloor sediments in the southwest study area,where the sediments are easily scoured and become coarser due to strong hydrodynamic conditions,are mainly composed of silty sand and sandy silt with high mechanical strength and low compressibility. The surficial seafloor sediments in the northeast study area consist mostly of silty clay and clayey silt with low mechanical strength and high compressibility. Sediments are not uniformin the seafloor,and often composed of a few types of sediments interbedded. The variation of fundamental physical properties and mechanical properties of the sediment with depth is mainly related to sediment types,and secondly compaction. To a certain extent,the fitting function proposed in this study can be used to estimate the porosity of seafloor sediment in the study area if the compressional wave velocity is known.