Effects of partial saturation on the collapse and swelling of geo-materials (Effets de la saturation partielle sur l'effondrement et le gonflement des géo-materiaux)

-在土木工程实践中发现的大部分土壤都部分被水饱和。在非饱和土中，吸力是土体孔隙中的空气压力和间隙水压力之间的孔压差。吸力是土壤颗粒之间粘结力的来源，这意味着毛细作用具有内聚力效应。与饱和土相比，非饱和土具有更好的抗力和更高的刚性。因此，土壤的工程性质取决于吸力和水分。近几年来，非饱和土改良岩土性质的室内表征研究取得了进展。实验室测试现在被设计为集成了音量和吸力控制。对观察到的行为也提出了概念性的解释，并导致了工程问题的数值模拟的实用工具。 -然而，在专业实践中，部分饱和仍然很少被考虑。根据非饱和土力学对基础和地下结构的优化设计和验算有一定的空间。一个特殊的应用领域是道路工程。在道路路基中发现的膨胀土和湿陷性土是重要的道路损坏的根源。路基的大而永久的变形现在可以与水的渗透过程有关，从而与部分饱和有关。 -该研究计划旨在改进在应力和部分饱和的复杂条件下的非饱和土壤的实验室特征。新获得的数据库将对土壤和其他地质材料中的变形和毛细作用机制产生关键的见解。实验结果为考虑毛管效应的膨胀土本构模型的建立奠定了基础。建议将开发的模型应用到商业软件中，以便实践工程师和研究人员可以访问研究计划的结果。该计算工具特别适用于路基、大坝工程和自然灾害预测。

- Most of the soils found in civil engineering practice are partially saturated with water. In unsaturated soils, the suction is the pore pressure deficiency between the air pressure in the pores of the soil and the interstitial water pressure. Suction is at the origin of bonding forces between the soil particles which means that capillarity has a cohesive effect. Unsaturated soils possess a better resistance and a higher rigidity compared with saturated soils. The engineering properties of the soil thus depend on suction and moisture. The laboratory characterization of the improved geotechnical properties of unsaturated soils has progressed recently. Laboratory tests are now designed to integrate both the volume and suction control. Conceptual interpretation of the observed behavior have also been proposed and led to practical tools for the numerical simulation of engineering problems. - However, partial saturation is still little accounted for in professional practice. There is room for optimizing the design and verification of foundations and underground structures in the light of unsaturated soil mechanics. One particular field of application is that of the road engineering. Swelling soils and collapsible soils, found in road subgrades, are at the origin of important road damage. The large, permanent deformations of road subgrades can now be related to the water infiltration process and thus to partial saturation. - The research program aims at proposing improvements to the laboratory characterization of unsaturated soils in complex conditions of stress and partial saturation. The newly obtained database will generate key insights into the mechanisms of deformation and capillarity in soils and other geo-materials. The experimental evidence serves as a basis to the formulation of a new constitutive model for expansive soils in the light of capillary effects. It is proposed to implement the developed model into a commercially available software so that practicing engineers and researchers can have access to the findings of the research program. The computing tool applies particularly to road foundation, dam engineering and prediction of natural hazards.