[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

비만아 부모의 돌봄 경험: q 방법론

The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.

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VALIDITY OF CUBIC LAW FOR FLUID FLOW IN A DEFORMABLE ROCK FRACTURE - eScholarship

The development of the Brazilian disc test for determining indirect tensile strength and its applications in rock mechanics are reviewed herein. Based on the history of research on the Brazilian test by analytical, experimental, and numerical approaches, three research stages can be identified. Most of the early studies focused on the tensile stress distribution in Brazilian disc specimens, while ignoring the tensile strain distribution. The observation of different crack initiation positions in the Brazilian disc has drawn a lot of research interest from the rock mechanics community. A simple extension strain criterion was put forward by Stacey (Int J Rock Mech Min Sci Geomech Abstr 18(6):469–474, 1981) to account for extension crack initiation and propagation in rocks, although this is not widely used. In the present study, a linear elastic numerical model is constructed to study crack initiation in a 50-mm-diameter Brazilian disc using FLAC3D. The maximum tensile stress and the maximum tensile strain are both found to occur about 5 mm away from the two loading points along the compressed diameter of the disc, instead of at the center of the disc surface. Therefore, the crack initiation point of the Brazilian test for rocks may be located near the loading point when the tensile strain meets the maximum extension strain criterion, but at the surface center when the tensile stress meets the maximum tensile strength criterion.

The Brazilian Disc Test for Rock Mechanics Applications: Review and New Insights

With the fast development of Chinese economy in recent years, China has become the largest coal production and consumption country in the world. Correspondingly, it has produced large quantities of mining waste including coal gangue, coal sludge, fly-ash, coal mine drainage and coal-bed methane (CBM) that are hazardous to the soil, air, and water. Based on the theory and practice of sustainable development and recycling economy, the paper will discuss and analyze the mining waste management in Jincheng Anthracite Mining Group, Shanxi Province, where they have found the paths to realize the mining waste reusing and recycling in colliery. They had established many green industrial chains in the mining waste treatment: the gangue piles turned into man-made eco-park, gangue used for power generation, fly-ash used in the building material, the coal mining water reused and recycled in closed pipelines, the CBM extracted for home-burning and electricity generation, etc. The coal mining waste has been converted into wealth and played more and more important roles in many fields. The practice indicated that these patterns can be applied in other coal mines.

Diyuan Li

Papers

The Brazilian Disc Test for Rock Mechanics Applications: Review and New Insights

Energy evolution characteristics of hard rock during triaxial failure with different loading and unloading paths

Influence of water content and anisotropy on the strength and deformability of low porosity meta-sedimentary rocks under triaxial compression

Fracture analysis of marble specimens with a hole under uniaxial compression by digital image correlation

Mechanical properties and fracture evolution of sandstone specimens containing different inclusions under uniaxial compression