• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.1159-1168
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• 2020

The conduits of agricultural reservoirs undergo deterioration over a considerable period of time and this is highly likely to cause structural problems such as cracks. It is therefore important to consider the effects of structural defects on the body from the viewpoint of stability and maintenance of the embankment. In this study, basic data on the effects of the crack location on the stability of the embankment is obtained by identifying, comparing, and analyzing the erosion characteristics and pore water pressure behavior through a large-scale model experiment that involves classifying the location of the conduit cracks. From the results of the experiment, it was confirmed that when a crack occurred, the amount of leakage increased as the location of the crack portion was closer to the water level, and the internal erosion phenomenon accelerated, thereby increasing the possibility of piping. It was also found that an upstream conduit crack affects the erosion and water pressure change of the central and downstream conduit of the embankment, and the conduit crack has a very large effect on the pore water pressure despite the low upstream water level. Therefore, the seepage behavior of the embankment for each conduit crack identified in this study is considered to be useful basic data for preparing a repair and reinforcement plan according to the crack location in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.353-359
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• 2010

Cementitious matrix based composites are vulnerable to the drying shrinkage crack during the curing process. In this study, the drying shrinkage induced fracture behavior of the fiber reinforced concrete is simulated and the effects of the fiber reinforcement conditions on the fracture characteristics are analysed. The numerical model is composed of conduit elements and rigid-body-spring elements on the identical irregular lattice topology, where the drying shrinkage is presented by the coupling of nonmechanical-mechanical behaviors handled by those respective element types. Semi-discrete fiber elements are applied within the rigid-body-spring network to model the fiber reinforcement. The shrinkage parameters are calibrated through the KS F 2424 free drying shrinkage test simulation and comparison of the time-shrinkage strain curves. Next, the KS F 2595 restrained drying shrinkage test is simulated for various fiber volume fractions and the numerical model is verified by comparison of the crack initiating time with the previous experimental results. In addition, the drying shrinkage cracking phenomenon is analysed with change in the length and the surface shape of the fibers, the measurement of the maximum crack width in the numerical experiment indicates the judgement of the crack controlling effect.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.315-325
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• 2001

A series of laboratory tests was conducted to observe damage process by stress and to understand characteristics of permeability related with rock damage. Rock specimens which were composed of the Cretaceous medium grained granites were experienced of damage stress between 65% and 95% of the compressive strength. Rock deformation by damage process was identified with the elastic wave velocity test. Relationship between rock damage and permeability change was also analyzed by water injection test in the laboratory. According to the results of the tests, damage tends to be occurred from stress level of 80% of the compressive strength and it reduces elastic wave velocity. The damaged specimens with stress more than 80% of the compressive strength showed crack density more than 0.6 and persistent length with good connectivity of cracks. They also have higher permeability than that of specimens with crack density less than 0.6. Considered with the above results, the rock specimens used in this study were fully damaged from stress level of 80% of the compressive strength. Crack initiation and propagation by damage caused good connectivity of cracks through rock specimen. These damage process, therefore, brought high permeability coefficient through water flow conduit in the rock specimen.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.5
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• pp.553-561
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• 2015

In this study, the performance assessment criterion for reasonable maintenance of shield TBM tunnel was presented. The performance assessment items such as crack, leakage, breakage, spalling, exfoliation/detachment, efflorescence, quality condition, exposure of steel, carbonation, faulting step, bolts condition, drainage condition, ground condition, contact section condition and conduit condition were selected by analyzing domestic and foreign performance assessment criterions and investigating segment lining deterioration cases through the site investigation and in-depth inspection analysis result on the shield TBM tunnel. In addition, the reasonable weight using AHP (Analytic Hierarchy Process) were estimated.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.135-142
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• 2007

Although rock itself has high strength or low permeability, engineering properties of rock masses are significantly influenced by discontinuities such as cracks and joints. Considered with possibility of groundwater flow in massive rock mass of deep subsurface, the connectivity of micro cracks should be analyzed as a conduit of ground-water flow. The objective of this study is to estimate permeability characteristics of granite dependent on damage process with application of joint distribution analysis and modeling of permeability analysis in rock masses. In case of average permeability coefficients, the modeling results based on micro cracks data are well matched with the results from permeability tests. Based on the visualization result of three dimensional model, the average permeability coefficients through the discharge plane have a positive relationship with the number of microcrack induced by rock damage.