Abstract Dredged sludge has poor mechanical properties and its safe disposal is highly risky. Fiber has been considered as an effective additive for soil reinforcement because of its cost effectiveness, easy adaptability, and reproducibility. The main objective of this research is to investigate the effects of polypropylene fiber on hydro-mechanical behavior of dredged sludge. A series of compression and direct shear tests were performed on dredged sludge samples with different percentage contents of polypropylene fiber 0%, 0.05%, 0.1%, 0.2%, 0.4%, and 0.8% by weight of dredged sludge and the direct shear tests were performed at vertical stresses of 50, 100, 200 and 400 kPa. The test results indicate that inclusion of fiber improves shear strength of sludge with increasing compression, void ratio, consolidation coefficient and hydraulic conductivity. The optimum fiber content for these improvements was found to be 0.1%. Presumably the post-consolidation moisture content of sludge after consolidation is minimal at this fiber content, although the shear strength continues to increase with fiber content even after consolidation. The shear strength of samples with the fiber contents of 0.8% is 1.48, 1.58, 1.42, 1.27 times that of the non-reinforced samples under respective consolidation pressures of 50, 100, 200 and 400 kPa, and the reinforcement efficiency is most significant under a pressure of 100 kPa. The strain hardening tendency is more pronounced with the increase of fiber content in the late shear failure process. The results of this study indicate that the mechanism of fiber reinforcement for the consolidation test is “bridging” as different from the shear strength test, which is “friction”. This realization should impact upon the failure patterns of fiber reinforced materials.

中文翻译：

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纤维增强疏浚污泥的水力学行为

摘要 疏浚淤泥力学性能差，安全处置风险大。纤维因其成本效益、易适应性和可重复性而被认为是一种有效的土壤加固添加剂。本研究的主要目的是研究聚丙烯纤维对疏浚污泥的水力学行为的影响。对聚丙烯纤维含量为0%、0.05%、0.1%、0.2%、0.4%和0.8%（按疏浚污泥重量计）的疏浚污泥样品进行了一系列压缩和直剪试验，并进行了直剪试验。在 50、100、200 和 400 kPa 的垂直应力下进行。试验结果表明，纤维的掺入提高了污泥的剪切强度，随压缩率、孔隙率、固结系数和导水率。发现这些改进的最佳纤维含量为 0.1%。据推测，固结后污泥的固结后水分含量在该纤维含量下是最小的，尽管即使在固结后剪切强度随着纤维含量的增加而继续增加。纤维含量为0.8%的试样在固结压力分别为50、100、200和400 kPa的情况下，其剪切强度分别是未增强试样的1.48、1.58、1.42、1.27倍，增强效率最显着。压力为 100 kPa。在后期剪切破坏过程中，随着纤维含量的增加，应变硬化趋势更加明显。本研究的结果表明，固结试验的纤维增强机制是“架桥”，不同于剪切强度试验的“摩擦”。这种认识应该会影响纤维增强材料的失效模式。