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首页> 外文期刊>E3S Web of Conferences >A Constitutive Model for Locally Drained Shear Bands in Globally Undrained Dense Sand
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A Constitutive Model for Locally Drained Shear Bands in Globally Undrained Dense Sand

机译：全球不排水稠密砂土中局部排水剪切带的本构模型

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When saturated granular materials which are dilative in nature are subjected to the undrained deformation, their strength increases due to the generation of negative excess pore pressure. This phenomenon is known as dilative hardening and can be witnessed in saturated dense sand or rocks during very fast loading. However, experimental evidence of undrained biaxial compression tests of dense sand shows a limit to this dilative hardening due to the formation of shear bands. There is no consensus in the literature about the mechanism which triggers these shear bands in the dense dilative sand under isochoric constraint. The possible theoretical reasoning is the local drainage inside the specimen under the globally undrained condition, which is challenging to be monitored experimentally. Hence, both incept of localisation and post-bifurcation of the saturated undrained dense sand demand further numerical investigation. Pathological mesh dependency hinders the ability of the finite element method to represent the localisation without advanced regularisation methods. This paper attempt to provide a macroscopic constitutive behaviour of the undrained deformation of the saturated dense sand in the presence of a locally drained shear band. Discontinuation of dilatant hardening due to partial drainage between the shear band and the adjacent material is integrated into the constitutive model without changing governing equilibrium equations. Initially, a classical bifurcation analysis is conducted to detect the inception and inclination of the shear band based on the underlying drained deformation. Then a post-bifurcation analysis is carried out assuming an embedded drained or partially drained shear band at gauss points which satisfy bifurcation criterion. The smeared shear band approach is utilised to homogenise the constitutive relationship. It is observed that the dilatant hardening in the saturated undrained dense sand is reduced considerably due to the formation of shear bands.
机译：当自然膨胀的饱和粒状材料经受不排水的变形时，由于产生负的过大孔隙压力，它们的强度增加。这种现象称为膨胀硬化，可以在非常快速的加载过程中在饱和的稠密沙子或岩石中看到。但是，稠密砂土不排水双轴压缩试验的实验证据表明，由于剪切带的形成，这种扩张性硬化受到了限制。在等速约束下，在致密膨胀砂中触发这些剪切带的机理尚无文献报道。可能的理论推理是在整体不排水的情况下样品内部的局部排水，这很难通过实验进行监测。因此，饱和不排水的致密砂的局部化和后分叉都需要进一步的数值研究。病理网格的相依性阻碍了有限元方法在没有高级正则化方法的情况下表示局部化的能力。本文试图在存在局部排水剪切带的情况下提供饱和致密砂土不排水变形的宏观本构行为。由于剪切带和相邻材料之间的部分排水而导致的膨胀硬化的中止被整合到本构模型中，而无需更改控制平衡方程。最初，进行了经典的分叉分析，以基于潜在的排水变形检测剪切带的开始和倾斜。然后进行分叉后分析，假设在满足分叉标准的高斯点处存在嵌入的排水或部分排水的剪切带。涂抹的剪切带方法用于使本构关系均匀化。可以看出，由于剪切带的形成，饱和不排水的致密砂土中的膨胀硬化明显减少了。

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