Cylindrical samples of sand consolidated with tetrahydrofuran hydrate were tested for their compressive strength and creep behavior under uniaxial compression. The samples were 15 cm in length and 7.5 cm in diameter and were tested at −10 °C. The results, when combined with our previous measurements on similar samples at −6 °C, show that the material becomes stronger by about 10% with decrease in temperature; otherwise, the slopes of the peak stress – strain rate curves are the same. These results are similar to those of sand consolidated with ice, except that in the latter case the increase in strength over the same temperature range is about 30%. Furthermore, the slope of the peak stress – strain rate curve for the hydrate-consolidated sand is almost zero, whereas for the ice-consolidated sand it is quite steep. Consequently, at strain rates below 10−5 s−1 the hydrate-consolidated sand is stronger, whereas at strain rates above 10−5 s−1 the ice-consolidated sand is the stronger material. Noticeable differences were also observed in the creep behavior of the hydrate- and ice-consolidated sands. At −10 °C, ice-consolidated sand failed in about 15 h under a stress of about 7 MPa, whereas hydrate-consolidated sand failed after 52.3 h under a stress of 12.2 MPa and some samples did not fail even after 540 h when subjected to a stress of 9.3 MPa. Key words: gas hydrates, ice, frozen sand, mechanical properties, compressive strength, creep behavior.
/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, 24, 1, pp. 160-63, 1987-02 Measurement of soil water content using the combined time-domain reflectometry -thermal conductivity probe Baker, T. H. W.; Goodrich, L. E. A two-pronged metal probe measures the thermal conductivity and apparent dielectric constant of soils in the laboratory and in the field. One prong acts as a transient line heat source probe in measuring thermal conductivity. The apparent dielectric constant of the soil is determined by the time-domain reflectometry (TDR) technique, using both prongs as a parallel transmission line. Volumetric water content is determined from the apparent dielectric constant, making use of an empirical relation valid for most soils. For volumetric water contents above about 8%, the apparent dielectric constant shows a strong dependence on water content and relatively small changes can be measured; sensitivity increases with water content. For volumetric water contents less than 8%, a soil-dependent empirical relation between water content and thermal conductivity has been developed that is most sensitive at lower water contents. The combined probe provides a means of monitoring the water content of soils over a wide range of values, in the field and in the laboratory. CanadianKey words: soil water content, time-domain reflectometry, thermal conductivity.Une sonde a double pointe mesure la conduction thermique et la constante diklectrique apparente des sols en le laboratoire et sur le terrain. Une pointe agit comme une source de ligne de chaleur transitoire pour mesurer la conductivite thermique. La constante diklectrique apparente du sol reste determinee par une technique de rkflectometrie en fonction du temps (TDR), utilisant les deux pointes comme ligne de transmission. La teneur en eau volumetrique est determinee en partant de la constante dielectrique apparente, au moyen d'une relation empirique valable pour la plupart des sols. Pour les teneurs en eau volumktriques supt5rieures a environ 8%, la constante dielectrique apparente depend fortement de la teneur en eau, et des changements relativement faibles peuvent &tre mesurks; la sensibilite augmente avec la teneur en eau. Pour les teneurs en eau volumktriques infkrieures a 8%, une relation empirique fonction du sol a Ct k dkveloppCe entre la teneur en eau et la conductivite thermique; cette relation est tres sensible aux teneurs en eau plus faibles. La sonde fournit un moyen de mesurer de facon continu...
/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, 19, pp. 511-517, 1982 Locating the frozen-unfrozen interface in soils using time-domain reflectometry Baker, T. H. W.; Davis, J. L.; Hayhoe, H. N.; Topp, G. C. The time-domain reflectometry technique was compared with the temperature measurement method for locating the frozen-unfrozen interface in water and sandy soils. This technique depends on the high-frequency (1-1000 MHz) electrical properties of water that change significantly and abruptly between the liquid and solid phases. Parallel wire transmission lines were inserted into the soil to guide electromagnetic pulses produced by a time-domain reflectometer (TDR). The frozen-unfrozen interface produced reflections measured by the TDR which were in turn used to locate the interface as it moved along the transmission line. In the laboratory it was possible to locate the interface using the TDR to within k0.5 cm and in the field to within +2.4 cm. These errors were equal to those associated with the temperature measurements. Canadian
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