Increased interest in protection of the environment has led to a need to be able to predict long-term movement of moisture, and contaminants, in the vicinity of shallow land disposal sites for various toxic and radioactive wastes. The advantages of locating potential sites in arid regions has led to a need to develop means for predicting moisture movements in fairly dry, partially saturated soils and for measurements of the hydraulic conductivities of such soils. A technique was developed in which thermocouple psychrometers and the instantaneous profile method were used to measure conductivities of soils with suctions as high as 80 atm. For one clay of low plasticity, the conductivity dropped from about 10−7 cm/s when saturated to almost 10−12 cm/s for degrees of saturation of the order of 30 percent. Measured conductivities were used in a finite element solution to Darcy's equation to predict final water content profiles. The predicted and measured profiles compared well, which suggests that the measured conductivities were tolerably accurate. Based on data presented, the proposed technique seems promising for conductivity measurements in clays with degrees of saturation between about 30 and 90 percent and in sands with 5 to 50 percent saturation.

/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. Geotechnical Journal, 20, 1, pp. 69-81, 1983 The prediction of total heave on a slab-on-grade floor on regina clay Yoshida, R. T.; Fredlund, D. G.; Hamilton, J. J. Reprinted from Canadian Canadian Geotechnical JournalThe prediction of total heave of a slab-on-grade floor on Regina clay S veral analytical methods for the prediction of total heave of desiccated, expansive soils have been proposed for various geo raphic regions. The proposed method herein is based on a general theory for unsaturated soil. The in-situ stress conditions, as a sessed from the corrected swelling pressure and the required soil moduli, are deduced from the constant volume oedometer test. iVtrification of the proposed method was accomplished using data accumulated from the m~nitoring of movements of a floor slab n a light industrial building in north-central Regina, Saskatchewan. A leak in a water line buried under the floor slab resulted in a f, aximum heave of about 106 mm. Of the three final pore-water pressure distributions assumed, the one where pressure is consbnt with depth and equal to atmospheric pressure appears to be representative of the field conditions corresponding to the max'mum measured heave. The measured heave represents 89% of the predicted heave for the zero pore-water pressure t distvbution. It is concluded that the proposed method of analysis, based upon a general theory for unsaturated soils, provides a practical method to accwately assess total heave. Plusieurs mCthodes analytiques de prkdiction du soultvement total des sols expansifs dtssCchCs ont Bt C proposkes pow diffkrentes rkgions gkographiques. La mCthode proposte ici est fondCe sur une thkorie gtnCrale des sols non saturCs. Les conditions de constraintes en place, telles que dtduites de la pression de gonflement corrigke, et les modules du sol necessaires sont ddduits d'un essai oedomktrique A volume constant.La ~Crification de la mCthode proposCe a Ct C faite A partir des donnCes accumulCes 101-5 de I'obsemation d'une dalle de plancher dans un bltiment industriel lCger dans le centre-nord du RCgina, Saskatchewan. Une fuite dans une conduite d'eau enterrCe sous cette dalle a provoquC un soultvement maximum de 106 mm. Des trois distributions finales de pression interstitielle suppodes, la pression interstitielle constante avec la profondeur et Cgale A la pression atmosphCrique semble Ctre representative des conditions du terrain correspondant au soultvement maximum. Le ...

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Interest in moisture movement in partially saturated soils has developed rapidly in recent years mainly as a result of increasing use of sites in arid regions for disposal of toxic industrial and radioactive wastes. In attempting to measure hydraulic properties of soils in arid regions, problems are encountered with measurement of large suctions. Accordingly, we investigated the possibility of using thermocouple psychrometers, which have a broader range than most other suction probes, for studies of moisture movement in unsaturated soils. In this paper, the general features of psychrometers are described, procedures for calibration and use are reviewed, and experimental data are presented and discussed. Psychrometric measurements were found to be reproducible within about ±10 to 30 percent over a range in suction of about 2 to 80 atm. Response times were typically less than an hour. Problems with corrosion of psychrometers were severe with strongly acidic soils but not with a basic soil. Independent measurements of suction provided quantitative evidence that psychrometric measurements are reliable. The conclusion is that psychrometers seem to be the most suitable devices now available for measuring suctions in relatively dry, partially saturated soils.

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