Abstract Problems of ultra-soft soils, with the characteristics of high water content and very low strength, have been gradually distinguished from those of typical soft soils in recent years to address the new requirements of ocean geotechnical engineering, such as the improvement of dredged fills and hazard assessment of submarine landslides. Focusing on effects of high water content and different shear strain rates on the undrained shear strength of ultra-soft soils, a series of experimental investigations were conducted, using a combination test method, on three types of fine-grained soils with different grain size distributions: kaolin soil, Bohai Sea soil, and South China Sea soil. After preparing ultra-soft soil samples with high water content two to three times the liquid limit, the relationship between the strength and the water content of the soil was analyzed. Then, the changing trend of strength with shear strain rates in a broader range of 0.001–20 s−1 was discussed. Based on the test results and theory of shear thinning behavior, a piecewise model for the ultra-soft soil strength was proposed. The piecewise strength model can adequately reflect the strength characteristics of ultra-soft soils at different shear strain rate ranges, and the parameters in the model can be measured, or simply estimated.

中文翻译：

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三种超软细粒土的分段强度模型

摘要 超软土具有含水量高、强度低的特点，近年来逐渐与典型软土区分开来，以满足海洋岩土工程的新要求，如疏浚填料的改善。海底滑坡的危险性评估。针对高含水量和不同剪切应变率对超软土不排水抗剪强度的影响，采用组合试验方法，对三种不同粒度分布的细粒土进行了一系列试验研究。 ：高岭土、渤海土、南海土。制备了高含水量两到三倍液限的超软土样品后，分析了土的强度与含水量之间的关系。然后，讨论了强度随剪切应变率在 0.001-20 s-1 的更广泛范围内的变化趋势。基于试验结果和剪切稀化行为理论，提出了超软土强度的分段模型。分段强度模型可以充分反映超软土在不同剪切应变率范围内的强度特性，模型中的参数可以测量，也可以简单估算。