Dredged soil is widely adopted in coastal geotechnical engineering projects, yet its cyclic shear behavior has not been fully explored. In this study, we utilize the DJZ-500 shear apparatus to explore the influence of normal stress (125, 250, 375, 500 and 625 kPa), shear frequency (0.005, 0.01 and 0.04 Hz), and shear displacement amplitude (1, 3, 6 and 10 mm) on the cyclic shear behavior of coastal dredged soil. Our findings indicate that as normal stress increases, so does shear strength, while an increase in shear frequency does not correspondingly elevate shear strength. Furthermore, we observe that an optimal amplitude of shear displacement contributes to augmented shear strength, whereas larger or smaller amplitudes do not yield higher shear strengths. The shear strength is contingent upon a specific combination of shear cycle, normal stress and displacement amplitude. In addition, distinct from the shear strength variation law mainly determined by the normal stress level and the displacement amplitude, the damping ratio is solely affected by the shear displacement amplitude. We put forth an empirical formula considering normal stress, shear displacement amplitude, and shear frequency, which can forecast the cyclic shear behavior of dredged soil. This study provides substantial technical and theoretical aid for the design of coastal and offshore structures to withstand cyclical loads, such as those induced by waves and tidal forces.

疏浚土在沿海岩土工程项目中被广泛采用，但其循环剪切行为尚未得到充分研究。在本研究中，我们利用 DJZ-500 剪切装置探讨了法向应力（125、250、375、500 和 625 kPa）、剪切频率（0.005、0.01 和 0.04 Hz）以及剪切位移幅度（1、 3、6和10 mm）对沿海疏浚土的循环剪切行为的影响。我们的研究结果表明，随着法向应力的增加，剪切强度也会增加，而剪切频率的增加并不会相应地提高剪切强度。此外，我们观察到剪切位移的最佳幅度有助于增强剪切强度，而较大或较小的幅度不会产生更高的剪切强度。剪切强度取决于剪切周期、法向应力和位移幅度的特定组合。此外，与主要由法向应力水平和位移幅值决定的抗剪强度变化规律不同，阻尼比仅受剪切位移幅值的影响。我们提出了一个考虑法向应力、剪切位移幅值和剪切频率的经验公式，可以预测疏浚土的循环剪切行为。这项研究为沿海和近海结构的设计提供了大量的技术和理论帮助，以承受周期性载荷，例如由波浪和潮汐力引起的载荷。