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，吸力对非饱和土的水力学行为的影响对于分析和预测非饱和土的稳定性和变形具有重要意义。对于大多数这些应用，吸力的范围可以从0到1000kpa。在非饱和砂的特殊情况下，发现了以下缺点：现有的本构模型继承了非饱和粘土模型的大部分概念，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（吸力乘以饱和程度）可能导致较大的值。这使得材料在选择毕夏普应力作为本构应力时的模拟几乎不可能。此外，大多数文献给出的实验对标定砂土流体力学模型的相关参数（如吸力对临界状态孔隙比和刚度的作用）的信息很少。目前的项目提出了一个实验计划的执行和数值工具的开发和校准，以正确和适当地模拟非饱和砂。它包括开发和实施新的控制方程，以避免上述缺点。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的水力学模型，并开发一套开放的免费软件来正确模拟非饱和砂。

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.