Abstract

Port development results in production of large quantities of dredged marine sediments. Once dredged, sediments often have high water contents and are pumped to near-shore or in-water bunded marine impoundments for port expansion. However, dredged material disposal to freshwater onshore or empty impoundments typically changes sedimentation conditions that may change the effective grain-size distribution, mineral specific surface areas, settling particle orientations, resulting in settling rate changes. Salinity, temperature, water content, mineralogy, filling rate, and organic matter content may also influence sediment settlement and resulting consolidation. This study investigates the effect of salinity and sediment mineralogy on sediment settlement behaviour when deposited in saltwater, freshwater, or to empty ponds. For this purpose, slurries of dredged mud and kaolinite with water contents of 1.7 times their liquid limit were prepared and disposed into a series of 1000 mm long, 50 mm wide, and 500 mm high settlement columns. Result shows that the sediments settle faster in saltwater than freshwater or air, through divalent surface complexation and flocculation provided by seawater Ca and Mg. However, this is true if the salinity remains below 10 PSU, but the mixed mineral dredge spoil ultimately provides the densest sediment and lowest water sediment interface.

摘要

港口开发导致产生大量疏浚的海洋沉积物。一旦疏浚，沉积物通常具有高含水量，并被泵送到近岸或水中的堤岸海洋蓄水池，用于港口扩建。然而，将疏浚材料处置到陆上淡水或空蓄水池通常会改变沉降条件，这可能会改变有效粒度分布、矿物比表面积、沉降颗粒取向，从而导致沉降速率发生变化。盐度、温度、含水量、矿物学、充填率和有机质含量也可能影响沉积物沉降和由此产生的固结。本研究调查了盐度和沉积物矿物学对沉积在咸水、淡水或空池塘中的沉积物沉降行为的影响。以此目的，制备了含水量为液体极限 1.7 倍的疏浚泥浆和高岭石浆料，并将其放入一系列长 1000 毫米、宽 50 毫米和高 500 毫米的沉降柱中。结果表明，通过海水Ca和Mg提供的二价表面络合和絮凝作用，沉积物在盐水中的沉降速度比淡水或空气快。然而，如果盐度保持在 10 PSU 以下，则情况确实如此，但混合矿物疏浚弃土最终提供了最密集的沉积物和最低的水沉积物界面。通过海水 Ca 和 Mg 提供的二价表面络合和絮凝。然而，如果盐度保持在 10 PSU 以下，则情况确实如此，但混合矿物疏浚弃土最终提供了最密集的沉积物和最低的水沉积物界面。通过海水 Ca 和 Mg 提供的二价表面络合和絮凝。然而，如果盐度保持在 10 PSU 以下，则情况确实如此，但混合矿物疏浚弃土最终提供了最密集的沉积物和最低的水沉积物界面。