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Volume 76 (2014)
- Issue 6 Pages 411-
- Issue 5 Pages 333-
- Issue 4 Pages 269-
- Issue 3 Pages 221-
- Issue 2 Pages 173-
- Issue 1 Pages 3-
Volume 76, Issue 6
Displaying 1-6 of 6 articles from this issue
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Hiroyuki HIRASHIMA2014 Volume 76 Issue 6 Pages 411-419
Published: 2014
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESS -
Osamu ABE, Shigeto MOCHIZUKI2014 Volume 76 Issue 6 Pages 421-429
Published: 2014
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSA weak layer consisting of non-rimed plate-type snow crystals that formed during the night of February 4-5, 2010, was observed on February 8, 2010, at the Shinjo Cryospheric Environment Laboratory. It was confirmed that the weak layer included not only crystals with broad branches, but also large dendrites, and the density of the weak layer was lower than the densities of those of other studies. The shear strength of the weak layer was nearly identical to that of normal snow with the same density. A micrograph of a thin section of the layer showed that a majority of the snow crystals were deposited individually and horizontally. Thus, it was assumed that the weak layer could possibly collapse while under shear stress, since the unique microstructures depend on the mechanical properties of single ice crystals. However, in the case of brittle failure, the shear strength of the basal plane of the single ice crystals was similar to that of the perpendicular plane. In the case of ductile failure, the shear strain rate under plastic deformation calculated for a typical overburden load showed susceptibility to collapse, but in nature, this was not observed. Therefore, another mechanism is needed to control the deformation.View full abstractDownload PDF (3153K) -
Kazuya AKIYAMA2014 Volume 76 Issue 6 Pages 431-440
Published: 2014
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSThe concept of avalanche size was introduced to develop a scale of avalanches obtained during four winter seasons from December 2001 to May 2005 on the east side of Mt. Gongendake (1104m a.s.l.), located at the western Maseguchi District in Nou Town, Niigata Prefecture. The relationship between avalanche size and frequency was investigated using 431 avalanche video images of the most avalancheprone slope on the east side of Mt. Gongendake. Research using avalanche size data in the United States (US size scale) has shown that avalanche size (S) and frequency (n) are described by the relationship (Log n =−αS+β), excluding minimum-size avalanches, and that the coefficient α varies over time and space. This study obtained a similar relationship, excluding minimum-size avalanches, with α and β coefficients of 0.65 and 3.7, respectively. Additionally, the coefficient α differed from one winter season to another and had a relationship with snowfall thickness or maximum snow depth. Therefore, a certain relationship exists between avalanche magnitude and frequency, but the coefficient α may be different from the snow condition of each winter season in the case of a same slope.View full abstractDownload PDF (2920K) -
Yoko KOBAYASHI, Hiroshi MATSUDA, Shinichi HOMMA2014 Volume 76 Issue 6 Pages 441-450
Published: 2014
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESS -
Azusa DEGAWA2014 Volume 76 Issue 6 Pages 451-460
Published: 2014
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESS -
Hao ZHENG, Shunji KANIE2014 Volume 76 Issue 6 Pages 461-480
Published: 2014
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSIn numerical analysis of frost heave phenomenon, elastic models for soil may overestimate stress more than nonlinear models. It is one opinion that the overestimation of stress is safe for structures subjected to frost heave. However, when simultaneously considering frost heave, according to Takashiʼ s equation, a large constraining stress reduces the frost heave. This underestimation of deformation may threaten the safety of structures in cold regions since a small frost heave will lead to a lower stress level. It becomes a paradox. Therefore, the objective of this research is to construct a nonlinear frost heave estimation model and then confirm the influences of the nonlinear Youngʼs modulus when considering the stress distribution and amount of frost heave. This paper proposes a numerical model that couples the heat transfer process with nonlinear stress analysis. The frost heave ratio is estimated by Takashiʼs equation, which was originally a one-dimensional practical equation widely applied in Japan. However, we expand Takashiʼs equation into multi-dimensionality by using an anisotropic parameter. This parameter distributes frost heave ratio in different directions. The model adopts Fourierʼs law for thermal analysis and latent heat is seriously evaluated by equivalent heat capacity method. More importantly, this paper includes the temperature and stress-dependent Youngʼs modulus, which requires the adoption of a nonlinear mechanical analysis. This is a critical characteristic of soil and a significant improvement to the linear frost heave model. Finally, for discussion, simple examples, simulations and experimental results are provided to clarify the difference between linear and nonlinear models.View full abstractDownload PDF (2671K)
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