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The presence of compliant pores in rocks is important for understanding the stress-strain behaviors under different stress conditions. This paper describes findings on the effect of compliant pores on the mechanical behavior of a reservoir sandstone under hydrostatic and triaxial compression. Laboratory experiments were conducted at reservoir temperature on Weber Sandstone samples from the Rock Springs Uplift, Wyoming. Each experiment was conducted at three sequential stages: (stage 1) increase in the confining pressure while maintaining the pore pressure, (stage 2) increase in the pore pressure while maintaining the confining pressure, and (stage 3) application of the deviatoric load to failure. The nonlinear pore pressure volumetric strain relationship governed by compliant pores under low confining pressure changes to a linear behavior governed by stiff pores under higher confining pressure. The estimated compressibilities of the matrix material in sandstone samples are close to the typical compressibility of quartz. Because of the change in pore structures during stage 1 and stage 2 loadings, the estimated bulk compressibilities of the sandstone sample under the lowest confining pressure decrease with increasing differential pressure. The increase in crack initiation stress is limited with increasing differential pressure because of similar total crack length governed by initial compliant porosity in sandstone samples. Key words: compliant pores, hydrostatic and triaxial compression, reservoir rocks. La presence de pores conformes dans les roches est importante pour comprendre les comportements contraintedeformation dans differentes conditions de contrainte. Cet article decrit les resultats concernant l'effet des pores conformes sur le comportement mecanique d'un reservoir de gres sous compression hydrostatique et triaxiale. Des experiences de laboratoire ont ete menees a la temperature du reservoir sur des echantillons du << Weber Sandstone >> du Rock Springs Uplift, dans le Wyoming. Chaque experience a ete realisee a trois etapes sequentielles : (etape 1) augmentation de la pression de confinement tout en maintenant la pression interstitielle, (etape 2) augmentation de la pression interstitielle tout en maintenant la pression de confinement et (etape 3) application de la charge deviatorique a l'echec. La relation pression interstitielle--deformation volumetrique non lineaire des pores, regie par des pores conformes soumis a de faibles pressions de confinement, se transforme en un comportement lineaire regi par des pores rigides soumis a une pression de confinement plus elevee. Les compressibilites estimees du materiau de la matrice dans les echantillons de gres sont proches de la compressibilite typique du quartz. En raison du changement de structure des pores lors des chargements des phases 1 et 2, les compressibilites apparentes estimees de l'echantillon de gres sous la pression de confinement la plus faible diminuent avec l'augmentation de la pression differentielle. L'augmentation de la contrainte a l'origine de la fissure est limitee par l'augmentation de la pression differentielle en raison de la longueur totale similaire de la fissure regie par la porosite conforme initiale dans les echantillons de gres. [Traduit par la Redaction] Mots-cles: pores conformes, compression hydrostatique et triaxiale, roches-reservoirs., 1. Introduction Understanding the relationship between rock mechanical properties and physical properties is important in different geological and geotechnical applications, such as hydraulic fracturing and carbon sequestration. The presence of [...]

Many cases of artificial soft clay foundation constructed by hydraulic filling and improved by the vacuum preloading show the clogging phenomenon in the surrounding soil, which compromises the improvement quality. To clarify the clogging mechanism and the formation of soil columns, the vacuum process was tracked from macro to micro by laboratory model tests. Results show that the soil column with higher strength (density) and lower water content was formed surrounding the prefabricated vertical drainage (PVD). Mercury intrusion porosimetry (MIP) tests revealed that the pore-entrance diameter of the soil column after 50 and 43 days of vacuum application ranged from 100 to 600 nm, and that at peak it is 300 nm. However, the mean diameter of the colloidal particles in tail water decreases from 1000 to 100 nm with continuous vacuum application, and then becomes stable at about 100 nm after 43 days. After re-visiting the vacuum process of the hydraulic reclamation mud, the pore-size distribution of surrounding soils and particle-size distribution of the tail water, the clogging was explained by the filling of the pores of the soil column by the colloidal particles in pore water. This mechanism differentiates the artificial foundation improved by vacuum preloading from the natural foundation for the presence of rich colloidal particles in pore water. Key words: vacuum preloading, hydraulic reclamation mud, clogging of soil column, colloid property of tail water, pore-entrance size distribution. De nombreux cas de fondations en argile molle artificielle construites par remplissage hydraulique et ameliorees par la precharge sous vide montrent le phenomene de colmatage dans le sol environnant, qui compromet la qualite de l'amelioration. Pour clarifier le mecanisme de colmatage et la formation des colonnes de sol, le processus de vide a ete suivi de macro a micro par des tests de modele de laboratoire. Les resultats montrent que la colonne de sol avec une plus grande resistance (densite) et une plus faible teneur en eau a ete formee autour du drainage vertical prefabrique (<< PVD >>). Les tests de porosimetrie au mercure (<< MIP >>) ont revele que le diametre d'entree des pores de la colonne de sol apres 50 et 43 jours de vide variait de 100 a 600 nm et que le pic atteignait 300 nm. Cependant, le diametre moyen des particules colloidales dans l'eau d'aval diminue de 1000 a 100 nm avec une application continue sous vide, puis devient stable a environ 100 nm apres 43 jours. Apres avoir revu le processus de vide de la boue de recuperation hydraulique, la distribution de la taille des pores des sols environnants et la distribution granulometrique de l'eau d'aval, le colmatage a ete explique par le remplissage des pores de la colonne de sol par les particules colloidales dans l'eau interstitielle. Ce mecanisme differencie la fondation artificielle amelioree par le prechargement sous vide de la fondation naturelle pour la presence de particules colloidales riches dans l'eau interstitielle. Mots-cless: precharge sous vide, boue de recuperation hydraulique, colmatage de la colonne de sol, propriete colloidale de l'eau d'aval, distribution de la taille de l'entree des pores., Introduction With the rapid development of Chinese coastal cities and the increase in population, the land resources are becoming more and more scarce, making marine reclamation very important. Haihua (also [...]

Abstract: An occurrence of diagenetic fluorapatite cement is documented within the Cambro-Ordovician Keeseville Formation, Potsdam Group, near Chateaugay in New York State. The fluorapatite cement occurs as stratiform layers within [...]