• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.627-634
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• 2002

To facilitate a drilling plan for grouting in fractured rock, an algorithm of practical use associated with a new term “fracture density distribution”or“fracture tomogram”is developed. It is well known that Televiewer data(amplitude and traveltime image) provide detailed information about not only dip and dip direction of each fracture but also its aperture size estimated by an appropriate evaluation algorithm. A selected plane section of medium around a borehole or the cross section between two boreholes is discretized into a two dimensional grid of cells(rectangular elements). As each elongated(straight) fracture passes through the cells, the corresponding aperture size value is successively summed up in each cell, depending on the fracture length segment. In this, the fracture lines can be determined by intersecting of each fracture plane with the selected plane section. If the fracture line does not pass through a particular grid element, the segment length is set to zero. The final value(aperture size value of each cell) derived from all the detected fractures constitutes the fracture density distribution of the selected plane section, Field examples are illustrated, which will prove the benefit of the suggested algorithm for several kinds of grouting works.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.215-218
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• 2005

We applied the density-surfactant-motivated method to the removal of DNAPL within a rough-walled single fracture. Observations are made to compare the DNAPL residual distribution before and after the flushing of surfactant-enhanced solution or water flushing. Results show that density-motivated method with surfactant-enhanced solution effectively removed DNAPL in a single fracture.

• Journal of radiological science and technology
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• v.23 no.2
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• pp.13-19
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• 2000

There were some controversies about direct cause of hip fracture. We attempted to look at 40 osteoporotic proximal femur fractures in women over 50 years between March in 1999 and Febuary in 2000. The bone density of the fracture group and the healthy 85 control group was measured by Dual Energy X-ray absorptiometry(DEXA). The result was compared using age matched paired T test. The results were as follows ; 1. The femoral neck fractures were 14 cases and the trochanteric fractures were 26 cases. Mean age at a fracture was 67.1 years in neck fracture group and 76.5 years in trochanteric fracture. 2. In the control group, the bone density of both side of the proximal femur was measured and it showed statistically no difference between both sides in same person. 3. The bone density of neck, Ward's triangle, trochanter(P<0.05) and lumbar spine(P<0.001) was significantly reduced in the proximal femoral fracture group comparing with the control group. 4. The bone density of neck, Ward's triangle, trochanter(P<0.05) was significantly reduced in the proximal femoral neck fracture group comparing with the control group, but there was no statistical difference in lumbar spine comparing with the control group. 5. The bone density of neck, Ward's triangle, trochanter and lumbar spine(P<0.001) was significantly reduced in the proximal femoral neck fracture group comparing with the control group. We concluded that the bone mineral densities(BMD) of proximal femur and lumbar spine had decreased in hip fractures but that the bone mineral density and T-score % of the proximal femur were statistically lower than that of the lumbar spine. We suggest that measuring the bone mineral density of the proximal femur may reflect the weakness of the proximal femur more precisely than measuring the bone mineral density of the lumbar spine.

• Geomechanics and Engineering
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• v.6 no.6
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• pp.613-624
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• 2014

The fractures in coal are the main migration and output channels of coalbed methane, directly influencing the permeability of the coal seams. It is of great significance to study the effect of fracture distribution in coals on the permeability of coal seam. The development rules of endogenetic and exogenetic fractures are different among various coal lithotypes. There is also difference in the fracture density for the same lithotype with different thicknesses. Through the observation and description of the macroscopic fractures in coal and the origin of fractures in coal, the effect of the coal lithotype and its thickness on fracture development in coal was discussed. It was found through the study that the density of fractures in vitrain band was the maximum for the same coal rank and thickness, followed by clarain band. There were few fractures developed in the durain band. However, the changes of fracture density in three types of bands presented different declining trends for low, medium and high coal rank. There were no fractures developed in the fusain. There were three variation patterns for the fracture densities at the same coal rank and coal lithotype: linear decrease, nonlinear decrease, and first decrease then remaining unchanged. However, the overall trend was that the fracture density decreased with the increase of thickness of coal band for the same coal rank and coal lithotype.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.455-469
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• 2007

The study area, Bonggil-ri, Gyeongju, SE Korea, is composed of Cretaceous sedimentary rocks, and Tertiary igneous rocks and dykes. A research on fracture developing history and density distribution was carried out on well exposed Tertiary granites. The fractures developed in this area have the following sequence; NW-SE trending duo-tile shear bands (set a), NNW-SSE trending extensional fractures (set d), WNW-ESE trending extensional or normal fractures (set b), NE-SW trending right-lateral fractures (set c), WNW-ESE trending reverse fault reactivated from normal faults (set e) and NW-SE trending left-lateral faults reactivated from shear bands (set a) under brittle condition. According to the result of fracture density analysis, the fracture density in this area depends on rock property rather than rock age, and also higher fracture density is observed around fault damage zones. However, this high fracture density may also be related to the cooling process associated with dyke intrusion as well as rock types and fault movement. Regardless of the reason of the high fracture density, high fracture density itself contributes to fluid flow and migration of chemical elements.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.113-120
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• 2004

Grouting works in fractured rocks have been performed to reinforce the underground and/or to block ground water flow at the foundation site of dam, bridge and so on. For the efficient grouting design, a prior knowledge of the fracture pattern of underground area to be grouted in very important. For the practical use, aperture sizes of open fractures that will be filled up with grouting materials will be kind of valuable information. Thus, the main purpose of this study is to develop a new technique (so called "GenFT") enable to form a three dimensional image of fracture aperture density distribution from Televiewer data. For this, the study is to focus on dealing with (1) estimating aperture size of each fracture automatically from Televiewer time image, (2) mapping extension of fracture planes on a given section, (3) evaluating aperture density distribution on the section by using both aperture size and fracture face mapping result of each fracture, (4) developing an algorithm that can transfer the previous results to any arbitrary(vertical and/or horizontal) section around the borehole. Since 3D imaging means "a strategy used to form an image of arbitrarily subdivided 2D sections with aperture density distribution", it will help avoid ambiguities of fracture pattern interpretation and hence will be of practical use not only for the design and assessment of grouting works but also for various engineering works. Examples of fields experiments are illustrated. It would seem that this technique might lead to reflecting future trend in underground survey.

• Structural Engineering and Mechanics
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• v.65 no.6
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• pp.699-706
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• 2018

In the present contribution, fracture resistance of U-notched GPPS members under mixed mode I/III loading conditions is assessed by using the Averaged Strain Energy Density (ASED) criterion. This criterion has been founded based on the ASED parameter averaged over a well-defined control volume embracing the notch edge. The validation of the theoretical criterion predictions is evaluated through comparing with the results of a series of mixed mode I/III fracture tests conducted on rectangular-shaped GPPS specimens weakened by a single edge U-notch. A recently developed apparatus for mixed mode I/III fracture experiments is employed for measuring the fracture loads of the specimens. The test samples are fabricated with different notch tip radii with the aim of evaluating the influence of this major feature of the U-notched components on the mixed mode I/III fracture behavior. It is shown that the onset of brittle fracture in U-notched GPPS specimens under various combinations of tension and out-of-plane shear can well be predicted by means of the ASED criterion.

• Steel and Composite Structures
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• v.34 no.5
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• pp.671-679
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• 2020

The new energy-based criterion, named Reinforcement Strain Energy Density (ReiSED), is proposed to investigate the fracture behavior of the cracked orthotropic materials in which the crack is embedded in the matrix along the fibers. ReiSED is an extension of the well-known minimum strain energy density criterion. The concept of the reinforced isotropic solid as an advantageous model is the basis of the proposed mixed-mode I/II criterion. This model introduces fibers as reinforcements of the isotropic matrix in orthotropic materials. The effects of fibers are qualified by defining reinforcement coefficients at tension and shear modes. These coefficients, called Reduced Stress (ReSt), provide the possibility of encompassing the fiber fraction in a fracture criterion for the first time. Comparing ReiSED fracture limit curve with experimental data proves the high efficiency of this criterion to predict the fracture behavior of orthotropic materials.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.543-547
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• 2003

We applied the modified invasion percolation (MIP) model to the migration of DNAPL within a two-dimensional random fracture network. The MIP model was verified against laboratory experiments, which was conducted using a two-dimensional random fracture network model. The results showed that the MIP needs modification. To remove TCE trapped in a random fracture network, the density-surfactant-motivated removal method was applied and found very effective to remove TCE from dead-end fractures.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.6
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• pp.306-316
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• 2013

Microstructure and fracture behavior of a multi-phase low-density steel were investigated. After hot-rolling and heat treatment, the microstructure of low-density steel was composed of coarse ferrite grains and elongated bands which include second phases such as austenite, martensite and ${\kappa}$-carbide depending on holding time during isothermal heat treatment. After tensile test, microcracks were observed at martensite or ${\kappa}$-carbide interface in the elongated bands. Coarse ferrite grains showed cleavage fracture behavior regardless of second phase. The cleavage fracture of ferrite could be attributed to their coarse grain size and solute atoms that increase ductile-to-brittle transition temperature of ferrite. Despite of the tendency of cleavage fracture in coarse ferrite grains, a specimen having coarse spheroidized ${\kappa}$-carbide particles in the elongated bands showed high total elongation of 30%. Thus, the easiness of plastic deformation in the elongated band seems to play an important role in retardation of cleavage crack formation in coarse ferrite grains.