Numerical analysis of a cylinder moving through rate-dependent undrained soil
Numerical analysis of a cylinder moving through rate-dependent undrained soil
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DOI：
10.1016/j.oceaneng.2010.08.005
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发表时间：
2011-05
影响因子：
5
通讯作者：
Hongxia Zhu;M. Randolph
中科院分区：
文献类型：
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作者：
Hongxia Zhu;M. Randolph
海底滑坡对管道潜在破坏的地质灾害评估需要一个定量模型来评估管道上的冲击力。与典型的岩土工程问题相比，在快速移动，流动状的海底滑坡的应变率通常要高得多，这将导致土壤强度的增强，从而导致更大的冲击力。一般来说，有两种可能的预测框架应变率依赖性：流体动力学框架和岩土工程框架。通过比较这两种方法中常用的流变模型，本文提出了一种统一的可加幂律模型，它是流体力学中Herschel-Bulkley模型的规范化形式。该模型已被用于结合大变形有限元方法来研究不排水极限载荷的圆柱体上移动稳定通过惯性较小的软率相关材料，以量化的应变率效应。探讨了剪切变稀指数和Oldroyd数对剪切区的影响及流动机理。计算的阻力因子进行了比较，从计算流体动力学分析获得的阻力系数。的平均应变率所经历的土壤流过的圆柱体估计为一个给定的流速和表达的形式，一个传统的承载力方程，但与剪切强度直接连接到归一化的流速，建议预测的泥石流所施加的粘性力的大小。
Geo-hazard assessment of the potential damage to a pipeline caused by a submarine landslide requires a quantitative model to evaluate the impact forces on the pipeline. In contrast with typical geotechnical problems, the strain rate within the fast moving, flow-like submarine landslide is typically far higher, which will lead to enhancement of the soil strength and therefore result in larger impact forces. Generally, there are two possible predictive frameworks for strain-rate dependence: a fluid dynamics framework and a geotechnical framework. By comparison of common rheological models adopted in these two different approaches, a unified additive power-law model, a normalised form of the Herschel–Bulkley model from fluid mechanics, is explored in this paper. This model has been used in conjunction with a large deformation finite element approach to investigate the undrained limiting loads on a cylinder moving steadily through inertia-less soft rate-dependent material, in order to quantify the strain-rate effects. The flow mechanism and the effects of the shear-thinning index and Oldroyd number on the shear zones are explored. The calculated resistance factors are compared with the drag coefficients obtained from computational fluid dynamics analysis. The average rate of strain experienced by the soil flowing past the cylinder is estimated for a given flow velocity and an expression in the form of a conventional bearing capacity equation, but with shear strength linked directly to the normalised flow velocity, is proposed to predict the magnitude of the viscous force exerted by the debris flow.