Developement and Implementation of a hydro-mechanical model for unsaturated sands

在许多工程结构和岩土工程应用中，吸力对非饱和土水力学性质的影响对于分析和预测非饱和土稳定性和变形具有重要意义。对于这些应用中的大多数，吸力的范围从0到1000 kpa。在非饱和砂土的特殊情况下，发现了以下缺点：现有的本构模型继承了大多数非饱和粘土模型的概念，导致在接近干燥状态时高估了材料的强度。在感兴趣的吸力范围内，毛细管应力(吸力乘以饱和度)可能会产生较大的值。这使得在选择毕晓普应力作为本构应力时几乎不可能对材料进行模拟。此外，文献中给出的大多数实验对用于标定砂土流体力学模型的相关参数的信息很少，例如吸力在临界状态下的孔隙率中的作用以及对刚度的影响。目前的项目提出了一项实验计划的执行，以及为正确和适当地模拟非饱和砂土而开发和校准数值工具。它包括开发和实施新的控制方程，以绕过上述缺点。通过对非饱和砂质边坡物理模型的模拟，对新的控制方程和本构模型进行了评价。在项目结束时，将有一套完整的实验来校准非饱和砂土的流体力学模型，并将开发一套用于正确模拟的无开放软件。

In many engineering structures and geotechnical applications, the influence of the suction on the hydro-mechanical behavior of unsaturated soils is of interest for the analysis and prediction of their stability and deformations. For most of these applications, the suction can range from 0 up to 1000 kPa. In the special case of unsaturated sands the following shortcomings have been detected: the existing constitutive models inherit most of their concepts from the models for unsaturated clays leading to an overestimation of the material strength when approaching to the dry state. Within the suction range of interest, the capillary stress (suction times the degree of saturation) can result in large values. This makes the simulation of the material when selecting the Bishop stress as constitutive stress almost impossible. In addition, most of the experiments given by the literature show little information about the relevant parameters to calibrate the hydro-mechanical models for sands, such as the role of the suction in the void ratio at the critical state and in the stiffness. The current project proposes the performance of an experimental plan and the development and calibration of the numerical tools for the correct and appropriated simulation of unsaturated sands. It includes the development and implementation of new governing equations to circumvent the aforementioned shortcomings. The new governing equations and constitutive models will be evaluated through the simulation of physical models of an unsaturated sandy slope. At the end of the project, a complete set of experiments to calibrate the hydro-mechanical model for unsaturated sands will be available, and a set of open-free softwares for its correct simulation will be developed.