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，吸力对非饱和土流体力学特性的影响是分析和预测其稳定性和变形的重要因素。 对于这些应用中的大多数，吸力范围可以从0到1000 kPa。 在非饱和砂土的特殊情况下，已经发现了以下缺点：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强度。在感兴趣的吸力范围内，毛细应力（吸力乘以饱和度）可能导致较大的值。这使得当选择Bishop应力作为本构应力时几乎不可能模拟材料。此外，大多数文献给出的实验显示，有关参数的信息很少，以校准砂的流体力学模型，如在临界状态下的孔隙比和刚度的吸力的作用。目前的项目提出了一个实验计划的性能和正确和适当的模拟非饱和砂的数值工具的开发和校准。它包括新的控制方程的开发和实施，以规避上述缺点。通过对一个非饱和桑迪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力学模型，并将开发一套开放的软件，以正确的模拟。

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.