长江口横沙东滩外侧建设人工岛的自然条件分析

Feasibility of natural condition to build an artificial island outside the Hengsha East Shoal in the Changjiang Estuary

利用2001-2008年的海图资料和2011-2012年枯季现场水文调查数据,分析长江口横沙东滩外侧海域的河势、水动力条件及泥沙含量的潮周期过程,讨论在此建设人工岛的自然条件。结果表明,横沙东滩外侧海域,2001-2008年间冲淤有变化,由滩向海的断面显示上部淤积,下部侵蚀,冲淤转换面在-7^-10m之间,-10^-20m海域整体呈现微冲趋势,但侵蚀速率减缓,河势趋于稳定。横沙东滩受北槽深水航道北导堤影响,向东南方向淤进。定点船测潮流表现出旋转流性质,枯季大潮最大流速不超过188cm/s,小潮最大流速小于134cm/s;北港口外的定点余流显示向口内输运,北槽口外则是向海输运。两测站数据显示枯季大小潮垂线平均含沙量处于0.061~0.116kg/m3之间,水体泥沙含量整体处在较低水平。从自然条件上来说,不考虑风浪影响情况,研究区域内河势渐趋稳定,水深条件良好,水动力条件适宜,水体含沙量较低,在该区域内建设人工岛具有可行性。

Shanghai harbor is to be built to an international shipping center, and needs deep-water harbor to meet the continuous increasing cargo transportation demands and larger vessels. Based on nautical charts during 2001 to 2008 and in-situ survey data obtained during 2011 to 2012, this paper discussed the feasibility of natural condition to build an artificial island outside the Changjiang Estuary. The results showed that the sea bed of the study area was stable, and its topography changed little from 2001 to 2008. Seven cross-section profiles showed that there was slight deposition in the upper part but erosion in the lower part, and the transforming depth from deposition to ero- sion was about --7 m to --10 m. The Hengsha East Shoal expands southeastwards due to the construction of north leading dike of the Changjiang Estuary deep-water navigation channel. The in-situ survey data showed that there was a rotary tidal current during the entire tide phase in winter,and the maximum current velocity was less than 188 cm/s during the flood of spring tide and no more than 134 cm/s during the ebb of neap. The residual cur- rent of the observation points showed some differences, e. g. ,it was transported into the estuary outside of North Channel, and it was transported toward the sea outside of Northern Passage. The in-situ average suspended sedi- ment concentration was 0. 061 kg/m^3 to 0. 116 kg/m^3 , corresponding to neap tide and spring tide, respectively. Based on analytical data provided above, we suggested that the hydrodynamic condition and the suspended concen- tration outside the Changjiang Estuary were suitable to build an artificial island, and weak local siltation could be expected due to rotary tidal current at the east edge of the Hengsha east shoal in the Changjiang Estuary.