Water saturation conditions in the rock masses around underground openings vary with place and time. For the long-term stability assessment of underground structures, it is essential to understand ...the effect of water on the time-dependent behavior of rocks. In this study, the effects of water saturation on the loading-rate dependence of strength, which is one of the time-dependent characteristics of rocks, were investigated both theoretically and via experiments. First, the effects of loading rate and water saturation on rock strength and its variability were clarified by means of a theory that is based on both stochastic and rate processes. Next, alternating loading-rate tests were conducted on Sanjome andesite using uniaxial compression testing under various water saturation conditions. The test results showed that the rock strength increases with a decrease in water saturation and that an increase in strength accompanied by a tenfold increase in loading rate is almost constant under various water saturation conditions. All of the test results were consistently explained by our theory of the dependence of rock strength and its variability under different loading rates and water saturation conditions. It was also found that the dependence of strength on the loading rate is equivalent to that on the water saturation, and that the strength obtained from a test could be converted to one under an arbitrary loading rate and water saturation condition. In addition, we proposed a constitutive equation based on these theoretical and experimental results that could reproduce the loading-rate dependence of stress-strain curves under various water saturation conditions using a single set of constants.
•Alternating loading-rate tests were conducted under various water saturation conditions.•An increase in strength with a tenfold increase in loading rate was independent of water saturation.•The theory consistently explained all the test results of strength and its variability.•The proposed equation could reproduce the test results using a single set of constants.
In order to investigate the influence of water vapor pressure in the surrounding environment on mode I fracture toughness (
K
Ic
) of rocks, semi-circular bend (SCB) tests under various water vapor ...pressures were conducted. Water vapor is one of the most effective agents which promote stress corrosion of rocks. The range of water vapor pressure used was 10
−2
to 10
3
Pa, and two anisotropic rock types, African granodiorite and Korean granite, were used in this work. The measurement of elastic wave velocity and observation of thin sections of these rocks were performed to investigate the microstructures of the rocks. It was found that the distribution of inherent microcracks and grains have a preferred orientation. Two types of specimens in different orientations, namely Type-1 and Type-3, were prepared based on the anisotropy identified by the differences in the elastic wave velocity.
K
Ic
of both rock types was dependent on the water vapor pressure in the surrounding environment and decreased with increasing water vapor pressure. It was found that the degree of the dependence is influenced by the orientation and density of inherent microcracks. The experimental results also showed that
K
Ic
depended on the material anisotropy. A fracture process was discussed on the basis of the geometry of fractures within fractured specimens visualized by the X-ray computed tomography (CT) method. It was concluded that the dominant factor causing the anisotropy of
K
Ic
is the distribution of grains rather than inherent microcracks in these rocks.
A method for characterising the wave-function of freely-propagating particles would provide a useful tool for developing quantum-information technologies with single electronic excitations. Previous ...continuous-variable quantum tomography techniques developed to analyse electronic excitations in the energy-time domain have been limited to energies close to the Fermi level. We show that a wide-band tomography of single-particle distributions is possible using energy-time filtering and that the Wigner representation of the mixed-state density matrix can be reconstructed for solitary electrons emitted by an on-demand single-electron source. These are highly localised distributions, isolated from the Fermi sea. While we cannot resolve the pure state Wigner function of our excitations due to classical fluctuations, we can partially resolve the chirp and squeezing of the Wigner function imposed by emission conditions and quantify the quantumness of the source. This tomography scheme, when implemented with sufficient experimental resolution, will enable quantum-limited measurements, providing information on electron coherence and entanglement at the individual particle level.
Although numerous genetic studies have been conducted for bipolar disorder (BD), its genetic architecture remains elusive. Here we perform, to the best of our knowledge, the first trio-based exome ...sequencing study for BD to investigate potential roles of de novo mutations in the disease etiology. We identified 71 de novo point mutations and one de novo copy-number mutation in 79 BD probands. Among the genes hit by de novo loss-of-function (LOF; nonsense, splice site or frameshift) or protein-altering (LOF, missense and inframe indel) mutations, we found significant enrichment of genes highly intolerant (first percentile of intolerant genes assessed by Residual Variation Intolerance Score) to protein-altering variants in general population, an observation that is also reported in autism and schizophrenia. When we performed a joint analysis using the data of schizoaffective disorder in published studies, we found global enrichment of de novo LOF and protein-altering mutations in the combined group of bipolar I and schizoaffective disorders. Considering relationship between de novo mutations and clinical phenotypes, we observed significantly earlier disease onset among the BD probands with de novo protein-altering mutations when compared with non-carriers. Gene ontology enrichment analysis of genes hit by de novo protein-altering mutations in bipolar I and schizoaffective disorders did not identify any significant enrichment. These results of exploratory analyses collectively point to the roles of de novo LOF and protein-altering mutations in the etiology of bipolar disorder and warrant further large-scale studies.
Effect of water on the strength and creep lifetime of andesite Hashiba, K.; Fukui, K.; Kataoka, M. ...
International journal of rock mechanics and mining sciences (Oxford, England : 1997),
August 2018, 2018-08-00, 20180801, Letnik:
108
Journal Article
Recenzirano
The authors’ research group has investigated the close relation between the time-dependent behaviors under various loading conditions through laboratory tests, theories, and constitutive equations. ...It is well known that water accelerates the time-dependent behaviors of rocks; water enlarges the loading-rate dependence of strength and shortens the time to failure (creep lifetime) under constant stress level (ratio of creep stress to strength). This paper introduced the theory in the previous studies based on the rate process theory and the stochastic process theory, and found that the theory disregarded the effect of a change in water conditions on the strength and creep lifetime of rocks. The theory was briefly modified and then applied to the strength, creep lifetime, and their variability in both dry and wet conditions. To validate the modified theory, strength tests and creep tests were conducted under uniaxial compression with Sanjome andesite. The constants in the modified theory were calculated from the strength, and then the creep lifetime collected from the creep tests was examined with the formulae derived from the modified theory. The test results in dry and wet conditions were consistently elucidated by the modified theory, which indicates that the strength and creep lifetime of Sanjome andesite are approximated by the simple formulae in the theory. Creep lifetime was estimated from strength, and the results in dry conditions were estimated from those in wet conditions and vice versa, based on this study.
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