Pierre Delage

Bio: Pierre Delage is an academic researcher from École des ponts ParisTech. The author has contributed to research in topics: Pore water pressure & Oedometer test. The author has an hindex of 46, co-authored 221 publications receiving 7289 citations. Previous affiliations of Pierre Delage include University of Liège & ParisTech.

Yielding and plastic behaviour of an unsaturated compacted silt

Abstract: Within the framework of an extended elastoplastic constitutive model for unsaturated soils (loading-collapse (LC) model), an experimental programme was performed in an osmotically controlled suction triaxial apparatus. The laboratory behaviour of a statically compacted silt was studied, and particular attention was given to the volume changes monitored during shear. Isotropic loading tests confirmed the main features of the LC model related to the effect of suction on volume changes, and allowed a direct determination of the LC curve. Constant σ3 and a few constant q shear tests were performed in order to study yielding and plastic flow at various increasing suctions, starting from the as-compacted condition. Several yield criteria were considered, depending on the type of test performed. Some similarities between compacted unsaturated soils and natural soft soils were shown, such as the inclined elliptical form of the yield curve, which results from the anisotropic state of stress prevailing during k0 co...

Study of the structure of a sensitive Champlain clay and of its evolution during consolidation

Abstract: Scanning electron microscopy and mercury intrusion porosimetry are used in parallel to identify the structure of a medium sensitivity Champlain clay. The clay structure is observed firstly on intac...

Microstructure of a compacted silt

Abstract: This paper presents a qualitative and quantitative study of the microstructure of a compacted silt, carried out using a scanning electron microscope and mercury intrusion pore size distribution mea...

Ageing effects in a compacted bentonite: a microstructure approach

Abstract: It is suspected that the as-compacted state of heavily compacted clays used as possible engineered barriers for nuclear waste disposal is time dependent, and that further change may occur in the material, even at constant water content and density. This paper presents an investigation of the time-dependent microstructure changes of an MX80 clay bentonite compacted at various dry densities and water contents. Microstructure investigation is based on mercury intrusion pore size distribution measurements and scanning electron microscopy (SEM). Results obtained by other researchers by using X-ray diffraction at low angles are also used. Statically compacted samples of MX80 were kept at constant volume and water content for various periods of time (1, 30 and 90 days) prior to mercury intrusion and SEM micro-structure investigation. A significant change in micro-structure with time was observed, characterised by a decrease in the inter-aggregate porosity and an increase in the very thin porosity not intruded by...

Effect of Temperature

Abstract: A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Suction Stress Characteristic Curve for Unsaturated Soil

Abstract: The concept of the suction stress characteristic curve (SSCC) for unsaturated soil is presented. Particle-scale equilibrium analyses are employed to distinguish three types of interparticle forces: (1) active forces transmitted through the soil grains; (2) active forces at or near interparticle contacts; and (3) passive, or counterbalancing, forces at or near interparticle contacts. It is proposed that the second type of force, which includes physicochemical forces, cementation forces, surface tension forces, and the force arising from negative pore-water pressure, may be conceptually combined into a macroscopic stress called suction stress. Suction stress characteristically depends on degree of saturation, water content, or matric suction through the SSCC, thus paralleling well-established concepts of the soil–water characteristic curve and hydraulic conductivity function for unsaturated soils. The existence and behavior of the SSCC are experimentally validated by considering unsaturated shear strength data for a variety of soil types in the literature. Its characteristic nature and a methodology for its determination are demonstrated. The experimental evidence shows that both Mohr–Coulomb failure and critical state failure can be well represented by the SSCC concept. The SSCC provides a potentially simple and practical way to describe the state of stress in unsaturated soil.

Références bibliographiques: La fibroscopie bronchique

Abstract: Méthodes : Sur une série de 31 femmes présentant des varices périnéales d’origine extrasaphéniennes ayant bénéficié d’une exploration radiologique veineuse pelvienne et de l’embolisation des veines incontinentes nous avons étudié les résultats et les corrélations anatomo-clinique entre les varices et les signes cliniques de l’insuffisance veineuse pelvienne. Un sous-groupe B de 23 patientes présentant une insuffisance veineuse pelvienne et des signes cliniques a été comparé à un groupe A de 4 patientes qui ne présentaient pas d’insuffisance veineuse pelvienne à l’exploration. Nous avons choisi d’étudier 3 signes cliniques : la douleur pelvienne et la douleur des membres inférieurs survenant au début ou pendant les règles ainsi que la dyspareunie. La symptomatologie a été évaluée sur une échelle analogique de 0 à 10 et un score clinique (de 0 à 30) a été établi en ajoutant ces 3 chiffres.