九龙江口海沧港区17～-18^#码头基槽浮泥成因分析

九龙江口海沧港区因建设17—18^#泊位而开挖的基槽处发育厚层浮泥．通过对该处浮泥及其周边的水体悬浮颗粒、海底表层和沉积物柱状样的激光粒度分析，发现浮泥的颗粒物主要由峰值粒径在7～10μm的粘土粉砂质细颗粒组分构成，但在浮泥层的下部还含有小部分峰值粒径为200—500μm的砂质粗颗粒组分．浮泥中细颗粒组分的粒度特征和水体中的悬浮颗粒、底质沉积物中的细颗粒组分一致，而浮泥中粗颗粒组分的粒度特征，和九龙江口洪水事件成因的中粗砂的粒度特征一致．结合现场调访和水文观测，得出17—18^#泊位基槽处浮泥的成因主要受海沧港区建设过程中产生的大量再悬浮泥沙以及受水下地形的影响，水动力条件适宜悬浮泥沙在17—18^#泊位基槽处聚淤．此外，台风引发的洪水也是增加悬浮泥沙含量的辅助因素．随着海沧港区的建成，水动力条件的改变，17～18^#泊位港池及调头区浮泥的厚度将小于基槽区浮泥厚度．

Formations of fluid-mud at the foundation trench of 17～18th wharves in Haicang Harbor of Jiulongjiang Estuary

Thick fluid mud layer formed in the foundation trench of 17 - 18^# wharves, Jiulongjiang Estuary. The granular metric analysis on the fluid mud, suspended particles in water, and sediments around the areas of the foundation trench found that particles of fluid mud was mainly composed of a fine-grained clay-silt population with a modal size of 7 - 10μm,and a coarse sandy component,with modal size range from 200 to 500μm,oecurred in the lower parts of fluid mud layer. The grain size frequency curves of the fine populations of fluid mud were consistent well with that of suspended particles in water and fine clay-silt population of sediments ,whereas the frequency curves of coarse population of fluid mud were similar to that of sandy population of sediments formed in flood events. Combined with field investigation and hydrological survey, it can be concluded that the thick fluid mud in the foundation trench of 17 - 18^# wharves was mostly resulted from high concentration suspended particles,affected by submarine topography and dredging and hydrological conditions which favored the siltation. The flood events caused by typhoon also promoted the formation of fluid mud by increasing the suspended particle in water. The thickness of fluid mud would decrease with the modification of hydrological conditions and when Haicang Harbor is formed.