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  • Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory  (35)
  • English  (35)
  • Undetermined
  • 2000-2004
  • 1990-1994  (11)
  • 1960-1964  (24)
  • 1
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    Model for avalanches in three spatial dimensions : comparison of theory to experiments (1994)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-94/5
    In: CRREL Report, 94-5
    Description / Table of Contents: A three-dimensional theory is derived to describe the temporal behavior of gravity currents of cohesionless granular media, in an attempt to model the motion of dense, flow-type snow avalanches, ice and rock slides. A mohr-Coulomb yield criterion is assumed to describe the constitutive behavior of the material, and the basal bed friction is described similarly by a Coulomb type of friction. A drag term is included in order to model the occurrence of flow regimes where boundary drag becomes non-negligible. Data from laboratory simulations are compared to a series of numerical studies based on the aforementioned theory. A nondimensional, depth and width averaged form of the theory is considered. A Lagrangian finite difference scheme is then applied to numerically model some limiting cases of the governing equations. Two different numerical models are developed, tested and compared to experimental values. The results indicate that the model can account for flow transitions by inclusion of the drag term when the initial inclination angle is large enough to affect boundary drag. Furthermore, the temporal and spatial evolution of the granulate and final runout position can be predicted to values well within the experimental error.
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    Pages: iv, 29 Seiten , Illustrationen
    Series Statement: CRREL Report 94-5
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a283989.pdf
    URL: https://hdl.handle.net/11681/9396
    Language: English
    Note: CONTENTS Preface Nomenclature Introduction Mathematical formulation Limiting cases of the governing equations Nondimensionalization scheme Numerical solutions and comparison to experiments Unconstrained Coulomb flow model with constant bed friction Unconstrained Coulomb flow with boundary drag term Conclusions and remarks Literature cited Abstract
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  • 2
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    Comparison of thawing soil strength measurements for predicting vehicle performance (1992)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-92/17
    In: CRREL Report, 92-17
    Description / Table of Contents: The CRREL Instrumented Vehicle (CIV), shear annulus, direct shear, andtriaxial compression devices were used to characterize the strength ofthawed and thawing soil. These strength values can be used in simpletraction models to predict the tractive performance of vehicles. Strength was evaluated in terms of the parameters c' and Φ' based on the Mohr-Coulomb failure criterion. It is proposed here that an instrumented vehicle is best suited for terrain characterization for mobility studies because the conditions created by a tire slipping on a soil surface are exactly duplicated. The c' and Φ' values from the shear annulus were found to overpredict traction because of the low normal stress applied by the annulus and the curved nature of the failure envelope. Of all the tests, the direct shear test yielded the highest Φ' value, most likely because the test was run at a slow deformation rate under drained conditions. The triaxial test results were the most similar to those from the vehicle. All test methods show Φ' increasingwith soil moisture up to the liquid limit of the soil and then decreasing. As measured with the vehicle, was also found to be strongly influenced by the thaw depth.
    Type of Medium: Series available for loan
    Pages: 17 Seiten , Illustrationen
    Series Statement: CRREL Report 92-17
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a258263.pdf
    URL: https://hdl.handle.net/11681/9145
    Language: English
    Note: CONTENTS Introduction Objective Background Strength measurement techniques Triaxial compression Direct shear Shear annulus device CRREL Instrumented Vehicle Discussion Comparison of methods Influence of soil conditions Traction prediction Conclusions References Abstract
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  • 3
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    Gas gun experiments to determine shock wave behavior in snow : methods and data (1993)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-93/11
    In: CRREL Report, 93-11
    Description / Table of Contents: A laboratory study of the behavior of snow under shock wave loading and unloading conditions was conducted using a 200-mm-diameter gas gun to generate loading waves in snow samples with initial densities of 100 to 520 kg m-3 at temperatures of -2 to -23 deg C. Stress levels were 2 to 40 MPa. The response of snow to shock wave loading was measured as a function of distance from the impact plane using embedded stress gauges. Large impedance differences between snow and the stress gauges produced complex stress histories. A finite element model, along with a simple analytical model of the experiment, was used to interpret the stress histories. Snow deformation was not affected by initial temperature, but was found to be rate dependent. The initial density of the snow determined its pressure-deformation path. The pressure needed to compact snow to a specific final density increases with decreasing initial density. The release moduli increased nonlinearly from 50 MPa at a snow pressure of about 15 MPa to 2700 MPa at a snow pressure of about 40 MPa.
    Type of Medium: Series available for loan
    Pages: iii, 150 Seiten , Illustrationen
    Series Statement: CRREL Report 93-11
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a270467.pdf
    URL: https://hdl.handle.net/11681/9163
    Language: English
    Note: CONTENTS Preface Introduction Experimental equipment and methods Gas gun Snow target assembly Data acquisition Experimental procedure Measured data Stress histories Snow characterization Data analysis Recommendations Experimental methods Experimental needs Summary Literature cited Appendix A : Stress-time data plots Appendix B: Tabulated stress-time data Abstract
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  • 4
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    Studies of salt ice; I: the tensile strength of NaCl ice (1961)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-202-80
    In: Research report / Cold Regions Research and Engineering Laboratory, 80
    Description / Table of Contents: From the Introduction: During the last few years, there has been an increased interest in developing a rational explanation for the rather considerable variation in such bulk properties of sea ice as its strength, density, thermal conductivity, latent heat of melting, and coefficient of thermal expansion. Of these properties, sea-ice strength has received by far the most attention for practical reasons.
    Type of Medium: Series available for loan
    Pages: iv, 30, A6, B10, C2, D5 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 80
    URL: https://hdl.handle.net/11681/5889
    Language: English
    Note: CONTENTS Preface Summary Introduction Experimentation Method of growing salt ice Strength test procedures Bulk properties of salt ice Phase relations Density and air content Strength results Strength of fresh-water ice Strength of NaCl ice as a function of brine volume Strength of NaCl· 2H2O ice as a function of the relative volume of solid salt Effect of thermal history on salt-ice strength Phase hysteresis Geometric hysteresis Effect of short-term cooling on the strength of fresh-water and NaCl·2H2O ice Effect of the volume of inclosed air on the strength of salt ice Conclusions NaCl ice Sea ice References Appendix A: Volume of brine and NaCl· 2H2O in NaCl ice as a function of salinity and temperature Appendix B: Ring test results Normal test sequences Appendix C: Ring test results Hysteresis test sequences Appendix .b: Ring test results Thermal history test sequences
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  • 5
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    The frost behavior of soils : laboratory and field data for a new concept; Part II: horizontal sorting (1962)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-202-85,2
    In: Research report / Cold Regions Research and Engineering Laboratory, 85,2
    In: The frost behavior of soils : laboratory and field data for a new concept, Part II
    Description / Table of Contents: Laboratory experiments were performed with a specil closed-system side-freezing cabinet in which completely saturated soil samples were subjected to alternate freeze-thaw cycles without surcharge. A vertical or nearly vertical freezethaw plane was obtained in the side-freezing cabinet. The soil used was a straight graded noncohesive material with 14 finer than the No. 200 0.074 mm mesh sieve. According to frost criterion based only on gradation, the soil would be classified as a never frost-heaving moraine soil or non-frost-susceptible. All experiments were run for 20 and 22 cycles. Freezing rates used were as follows 30.0 mmhr 33.0 mmhr and 4 .0 mmhr. The initial dry density was approximately constant for each test at 1.8 gcm3 or 112.4 lbft3, and complete saturation was maintained in the tests.
    Type of Medium: Series available for loan
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 85,2
    URL: https://apps.dtic.mil/sti/citations/AD0288295
    Language: English
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  • 6
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    Size distribution and liquid water content of fog, northwestern Greenland (1962)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-202-100
    In: Research report / Cold Regions Research and Engineering Laboratory, 100
    Description / Table of Contents: From the Summary: During the summer of 1960, observations were made of ground fog on the Greenland Ice Cap and of sea fog in the Thule area in northwestern Greenland. A microscope-stage-fog impactor was designed, and its collection efficiency determined both empirically and by computation from the theoretical work of Langmuir and Blodgett (1946). The empirical efficiency was found to be considerably greater than the theoretical efficiency.
    Type of Medium: Series available for loan
    Pages: iv, 13 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 100
    URL: https://hdl.handle.net/11681/5899
    Language: English
    Note: CONTENTS Preface Summary Introduction Method Design and operation of the impactor Collection efficiency Computation from theoretical values of Langmuir and Blodgett Empirical values Observations and results Fog on the ice cap Sea fog near Thule Discussion Conclusions References
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  • 7
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    Petrographic characteristics of young sea ice, Point Barrow, Alaska (1962)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-202-101
    In: Research report / Cold Regions Research and Engineering Laboratory, 101
    Description / Table of Contents: Partial Summary: This paper is a pilot study of interrelations between structural features readily observed in horizontal thin sections of sea ice under low magnification. The core studied was 31.4 cm in length and was collected from Elson Lagoon at Point Barrow, Alaska on 26 October 1960.
    Type of Medium: Series available for loan
    Pages: iv, 11 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 101
    URL: https://hdl.handle.net/11681/5910
    Language: English
    Note: CONTENTS Preface Summary Introduction Petrographic characteristics Intercrystalline features Intracrystalline features References
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  • 8
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    Effective thermal conductivity of ventilated snow (1963)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-202-103
    In: Research report / Cold Regions Research and Engineering Laboratory, 103
    Description / Table of Contents: Summary: The effect of air flow on the thermal conductivity of snow was investigated. Steady-state temperature measurements were made along the edge and axis of a cylindrical bed of snow to determine the effective axial thermal conductivity of snow. Unconsolidated snow samples were used, with densities ranging from 0.376 to 0.472 g/cm^3 and corresponding snow particle sizes of 0.065 to 0.219 cm nominal diameter; the mass flow rates employed ranged from approximately 10-40 x 10^-4g/cm^2 sec. Snow density and sample size apparently have opposite effects on the effective thermal conductivity because of the flow of fluid in snow. The test apparatus is described in detail and is illustrated. The results of the experiments are tabulated, and a least square equation is given which represents the results well.
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    Pages: iv, 14, A2 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 103
    URL: https://hdl.handle.net/11681/5850
    Language: English
    Note: CONTENTS Preface Summary Introduction Theory Apparatus and experimental procedure Results and discussion References Appendix A: Sample calculations of a and ke
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  • 9
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    Formation of lake ice in a temperate climate (1963)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-202-107
    In: Research report / Cold Regions Research and Engineering Laboratory, 107
    Description / Table of Contents: Summary: The formation of lake ice was studied during the winter of 1956-57 at Post Pond, Lyme, N. H. Tabular, columnar, granular, and crenulate textures of 36 blocks of ice observed are discussed in terms of relative growth velocity and shown in a classification chart. Ice structures are characterized by Forel striations, Tyndall figures, bubbles and strain shadows. Average crystal areas increased with ice thickness, the rate of increase being greater toward lake center, and ceased to enlarge when in a continuous bubble layer. The lake-ice sheet grew both from top and bottom, .downward growth resulting from crystals in a favorable vertical orientation of a-axes and upward growth coming about by water flowing on the original upper ice surface and freezing. Exception to this type of growth was found in the lake area which froze first, where individual crystal areas were larger at the surface and there was no upper surface ice accretion. Fabric diagrams of ice outside the anomolous area show a change of optic axis orientation from a high percentage of c-axes vertical near the surface to a high percentage horizontal at the bottom.
    Type of Medium: Series available for loan
    Pages: iv, 22, A2, B1 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 107
    URL: https://hdl.handle.net/11681/5847
    Language: English
    Note: CONTENTS Preface Summary Description of the lake Cli rna te of the lake Methods of study Ice textures Crystal size Ice structures Crystal fabric studies Growth of an ice sheet References Appendix A: Weather data Appendix B: Sample data
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  • 10
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    Operator variance in the determination of the plastic limit (1963)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-202-117
    In: Research report / Cold Regions Research and Engineering Laboratory, 117
    Description / Table of Contents: Summary: An experiment was designed to investigate operator-variance in the determination of the plastic limit of cohesive soils, independent of sample preparation and hydration time. A standard sample was prepared by dry-mixing commercial clay, "Grundite", with a pure silt. After the sample was hydrated for 3 weeks, five random samples were taken and five replicates performed on each sample. Analysis of variance (AOV) shows that there is no reason to doubt that the sample is homogeneous at the 0.05 level of significance. Random samples were then distributed to five zones of operators, where a zone is defined as a group of operators with similar backgrounds and engineering interests. Two operators from each group performed five replicates. The AOV model used in the analysis is mixed with the upper level fixed and the two lower levels random. The estimated "within" and "between" operator variances are 0. 45 and 4. 18 respectively. The estimated "between zones" contribution to the total sum of squares is negative. No correlation was found between an operator's internal variance and his deviation from the grand mean. On the basis of this experiment, no reason-exists to doubt that an "untrained" operator can obtain results comparable to those of professional operators. The major factor contributing to the total sample variance is the inconsistency between the individual operators who, although able to duplicate their own determinations, do not call the same end point. To minimize between operator variance, a readily prepared standard sample is suggested with which any operator can calibrate his plastic limit determinations against the expected national average.
    Type of Medium: Series available for loan
    Pages: iv, 8 Seiten , Illustrationen
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory 117
    URL: https://hdl.handle.net/11681/5857
    Language: English
    Note: CONTENTS Preface Summary ­Introduction Sample preparation Sample homogeneity Distribution of samples Analysis Conclusions and suggested standardization References
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