摘要:

This paper presents the results of a series of large scale direct shear tests performed on lake ice. Test specimens were oriented with the principal stresses acting in the plane of the ice sheet, approximately normal to the long axes of the columnar crystals. Sample dimensions were large in comparison with mean crystal diameter, reducing the possibility of deviations introduced by size effects. Although a number of assumptions are made concerning stress conditions at failure, results for uniform, artificially ‘seeded’ test pond ice indicate a failure mechanism that is frictional and consistent with triaxial test data reported elsewhere. Post-peak shear resulted in the formation of a distinct failure zone that also displayed a frictional response. The direct shear test described is robust and simple, does not require elaborate sample preparation, and may present an alternative method of strength determination for ice mechanics problems where the shear box configuration duplicates field stress conditions and constraints.

ISSN:0008-3674    

DOI:10.1139/t75-021

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Length change experiments on carbonate rock samples indicate that the thermal coefficient of expansion (contraction) from normal room temperature to below freezing is a function of the sorptive characteristic of the rock. The highly adsorptive rocks,i.e. those adsorbing more than 40% of their water from near 100% humidity atmosphere, show an increased thermal contraction coefficient in the saturated state over their dry state. The low adsorptive rocks have the same thermal expansion coefficients either in a dry or saturated state.The highly adsorptive rocks expand isothermally upon saturation. The average isothermal expansion of a group of nine rocks was equivalent to the dry thermal expansion of a 78 °C temperature change. The low adsorptive rocks showed a small net isothermal contraction upon wetting.The results indicate that the thermal coefficients of expansion obtained below the 100 °C range must specify the saturation conditions of the rock, and may differ for dry and saturated rock. A mechanism of weathering of highly adsorptive rocks is suggested, based on isothermal expansion and contraction of these rocks in dry and saturated states respectively. If confined, as in concrete, such rocks may generate destructive expansive forces upon wetting.

ISSN:0008-3674    

DOI:10.1139/t75-022

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Investigations have been undertaken on aspects of the slow creep of the snow pack on mountain slopes in southern British Columbia. Studied particularly were (1) the rate of slip of the basal layer of snow on its substratum, (2) the pressures applied by the creeping snow pack on some stationary obstacles, and (3) the regional and the year-to-year variations of such pressures. Simple, relatively inexpensive equipment and methods have been developed to explore these problems. These indicate, for example, basal creep velocities up to 90 cm/winter season on very steep slopes, and pressures in the order of 0.5 kg/cm2under extreme conditions. These studies lead to guidelines for future site investigations of areas subject to snow creep.

ISSN:0008-3674    

DOI:10.1139/t75-023

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The data collected at a warm-oil test pipeline at Inuvik. N.W.T. are analyzed making use of the theory of thaw–consolidation proposed by Morgenstern and Nixon. The observed pore pressures, settlements, and rate of melting in the thawing permafrost foundation have been compared with their corresponding theoretical predictions. Bearing in mind the natural variability of ice-rich permafrost deposits, the agreement between prediction and observation is extremely encouraging. As the data collected at this test facility form the only completely documented case history of a thawing foundation in permafrost published to date, this comparison between theory and actual performance is valuable in establishing a level of confidence in the application of the theory of thaw–consolidation.

ISSN:0008-3674    

DOI:10.1139/t75-024

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Specific heat measurements have been made on several soil materials at different temperatures in order to obtain a generalized functional relation between specific heat and temperature. Specific heats were found to vary linearly with temperature from 200 to 300 °K (−73 °C to + 27 °C) and extrapolated close to zero at 0 °K. Consequently, the functional relation between specific heat and temperature for soil materials may be approximated asCp = mTwhereCpis the specific heat,Tis the absolute temperature (°K), andmis a proportionality constant. Such a relation permits the prediction of the specific heats at any temperature normally encountered in the field once reliable specific heats have been determined at a single temperature.

ISSN:0008-3674    

DOI:10.1139/t75-025

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Roads and runways in Northern Canada often must carry exceptionally heavy loads. In order to design for these loads, a procedure has been developed which enables the prediction of fatigue life of pavements. Experimental evidence indicates that the definition of resilient deformation, which controls fatigue life of pavements, can be resolved in terms of stress state variables. The resilient modulus is defined in terms of (σ1– σ3), (σ3–ua), and (ua–uw) which is applied in a theoretical analysis. Typical forms of the constitutive relationships are presented. The effect of freeze–thaw cycles does not appear to produce significant hysteresis in the constitutive relationships.

ISSN:0008-3674    

DOI:10.1139/t75-026

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

In order to simplify the calculations of bending moments in floating ice plates subjected to slowly moving loads or static loads of short duration, influence functions for infinite plates floating on a liquid are derived and then presented graphically in the form of influence charts. The presented charts and analyses are based on the elastic theory of plates. It is shown how to use the charts in practice. Two numerical examples are presented.

ISSN:0008-3674    

DOI:10.1139/t75-027

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Tailings dams differ from conventional earthfill structures in that much more time is available to optimize design since their construction is extended over a longer period. Laboratory data are presented on a variety of tailings sands which indicate that they are relatively strong and incompressible. Poor performance is likely to result from inadequate seepage control and instability due to liquefaction. In order to take advantage of opportunities for ongoing design,in situpermeability and density monitoring is needed together with pore pressure measurements. An infiltration test for the determination of permeability above the water table is proposed.In situdensity determinations are made by driving a nuclear probe into the sands. The latter technique offers considerable promise for evaluating liquefaction potential of natural and fill deposits. Field experience is used to illustrate the application of the techniques.

ISSN:0008-3674    

DOI:10.1139/t75-028

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A rheological model is given which is capable of representing the continuing secondary foundation settlements reported in certain field observations of structures experiencing large variations in live load; similar observations have been made in the laboratory for specimens subjected to repeated loading. It is expected that the given model will prove useful in the long-time stress analysis of flexible structures, such as oil tanks, which are subjected to large variations in load.

ISSN:0008-3674    

DOI:10.1139/t75-029

出版商:NRC Research Press    

年代:1975

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t75-030

出版商:NRC Research Press    

年代:1975

数据来源: NRC