• Geotechnical Engineering
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• v.14 no.5
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• pp.219-234
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• 1998

Modulus measurements in vertical boreholes under simulated horizontal in-situ stress conditions were performed on laboratory rock specimens. The experimental program was focused on the examination of modulus change with the variation of the orientation, magnitude and ratios of horizontal biaxial stresses. The experiment results show that the modulus increases when the magnitude of the horizontal stresses increases. The modulus measured in the minimum principal direction increased when the ratio between the horizontal principal stresses increased, while the modulus measured in the maximum principal direction decreased when the ratio of the horizontal principal stresses increased. These were caused by the tangential stresses that vary depending upon the magnitude of horizontal stresses, the applied pressure and the orientation of measurement. Also, the measured moduli were determined under tensile stress, compressive stress, or both stresses. Thus, the stress effect on deformation modulus should be considered, not only for the interpretation of the results of borehole deformability measurement, but also for the design of underground gas storage and pressure tunnel, and for the interpretation of tunnel monitoring.

• Coupled systems mechanics
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• v.7 no.3
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• pp.333-351
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• 2018

In the present paper, the behavior of the Karaj double curvature arch dam is studied focusing on the effects of structural nonlinearity on the responses of the dam body when an underwater explosion occurred in the reservoir medium. The explosive sources are located at different distances from the dam and the effects of the cavitation and the initial shock wave of the explosion are considered. Different amount of TNT are considered. Two different linear and nonlinear behavior are assumed in the analysis and the dam body is assumed with and without contraction joints. Radial, tangential and vertical displacements of the dam crest are obtained. Moreover, maximum and minimum principal stress distributions are plotted. Based on the results, the dam body responses are sensitive to the insertion of joints and constitutive model considered for the dam body.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.473-476
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• 2000

Recently, many studies focus on mixed-mode fatigue-fracture characteristics of characteristics of materials. In order to reveal crack initiation and propagation mechanisms in combined -mode fatigue. This paper investigates the initiation and propagation behavior of the fatigue crack of the STS304 specimens under mixed mode loading conditions. moreover crack arrest and branch phenomena were analyzed with respect to the change do the angle of inclined loading. The relationship between the angle of inclined loading and the angle of branched crack was studied. A greate number of cycles are necessary to initiate a new crack from the initial crack. The direction of the new crack propagation is determined by MTS theory.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.761-769
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• 1994

Actual load acting on rail surface in the track is the combined mode loading due to the contact rolling load of the wheels. To investigate the fracture behavior on rail steel under combined modes I and II, fracture tests were performed by using the test jigs and fracture specimen which were designed by Richard. The analysis results of experimental fracture data were compared with various fracture criteria that have been introduced for determination of the crack propagation direction and the critical stress of fracture of a crack submitted to a mixed mode loading. From the results, it was shown that the actual crack propagation direction of rail steel agree with the crack propagation directions predicted by maximum tangential stress criterion and strain energy density criterion, and that fracture criterion follows principal strain criterion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.423-430
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• 2012

In this paper, the effect of wrinkling on the cut propagation direction of thin membrane was studied using geometrically nonlinear shell element post-buckling analysis. In the analysis, rectangular tensile membrane configuration with a slanted center cut was considered. The cut propagation direction was predicted by maximum energy release rate method, $K_{II}$-zero method, and maximum tangential stress method. The cut propagation angle and the $J$-integral values were calculated for the wrinkled and unwrinkled cases and the results were compared. Various initial cut orientation angles were considered and the effect on the propagation direction was studied. The cut propagation paths were also predicted by virtual cut extension approach.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1446-1455
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• 2000

Fatigue crack initiation and propagation behavior under cyclic biaxial loading has been investigated using thin-walled tubular specimen with a hole. Two types of biaxial loading system, i.e. cyclic tensile loading with super-imposed static torsional load and cyclic torsional loading with superimposed static tensile load, with various values of the biaxial loading ratio, $\tau$ s/ $\sigma$ max (or $\tau$ max/ $\sigma$s) were employed. Fatigue tests show that fatigue crack near the hole initiates and propagates at 900 and 450 direction to the longitudinal direction of the specimen under cyclic tensile and torsion loading with static biaxial stress, respectively, and the static biaxial stress doesn't have any great influence on fatigue crack initiation and growth direction. Stress analysis near the hole of the specimen shows that the crack around the hole initiates along the plane of maximum tangential stress range. Fatigue crack growth rates were evaluated as functions of equivalent stress intensity factor range, strain energy density factor range and crack tip opening displacement vector, respectively. It is shown that the biaxial mode fatigue crack growth rates can be relatively consistently predicted with these cyclic parameters.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.13-19
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• 2015

This paper presents a hydraulic fracture propagation model to describe propagation more realistically. In propagating the hydraulic fractures, we have used two criteria: maximum tangential stress to determine the fracture initiation angle and whether a hydraulic fracture intersects a natural fracture. The model was validated for the parameters relevant to fracture propagation, such as initiation angle and crossing ability through natural fracture. In order to check whether a hydraulic fracture crosses a natural fracture, the model results on crossing state excellently matched with the experimental data. In the sensitivity analysis for direction of maximum horizontal stress, frictional coefficient of fracture interface, and natural fracture orientation, the results show that hydraulic fracture intersects natural fracture, and then, propagated suitably with theoretical results according to fracture interaction criterion. In comparison of this model against vertical fracture approach, it was ascertained that there are discrepancies in fracture connectivity and stimulated reservoir volume.

• Journal of the Korean Wood Science and Technology
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• v.19 no.1
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• pp.31-63
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• 1991

It was proved that in conventional kiln drying of disks piling position in the kiln exerted a great influence on drying rates, and the larger the variation of disk diameter, the more undulating drying rates of disks. While in vacuum drying disks there was no influence on drying rates. By the end-wrapping treatments and the radial direction of disks tangential surface stresses in the core of disks were slightly compressive in three species. In control disks the drying stresses distributed into one step-style that compressive stresses in the pith side of 6cm from pith were larger than those in the bark side, while in the disks end-wrapped with Korean paper the drying stresses distributed uniformly, because flow rates of free water in disks had no difference between heart-and sap-wood by obstruction of evaporating water from surface of disks by end-wrapping with Korean paper. And end-wrapping with Korean paper considerably restrained those. Tangential differential shrinkage stresses developed the maximum tensile stress near the bark and with approaching the pith the stresses gradually reduced and changed into compressive stresses in near the pith. At the end of vacuum drying the maximum tangential tensile stresses of disks end-wrapped with Korean paper were smaller than those of control disks, and critical moisture contents causing the V-shaped crack of disks end-wrapped with Korean paper were lower than those of control disks because of the set by obstruction of evaporating water of end-wrapping with Korean paper. In the experiment of vacuum drying stress distribution the disks end-wrapped with Korean paper or aluminum foil in three species were free from V-shaped cracks and control disks were defected very slightly by V-shaped cracks. And also disks end-wrapped with Korean paper were free from heart checks in Alnus japonica and Juglans sinensis, and heart checks were occurred very slightly in others. Especially, not to speak of disks end-wrapped with Korean paper, vacuum drying of disks end-wrapped with aluminum foil prevented effectively drying defects, moreover drying times could be shortened, that is. Ginkgo biloba, Alnus japonica, and Juglans sinensis disks could be dried from green to in-use moisture content in 110 hours, 272 hours, and 407 hours, respectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.557-568
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• 2016

Squeezing is a phenomenon that may occur in deep tunneling and could bring about a large plastic deformation, tunnel closure and collapse of tunnel supports. Therefore, quantitative estimations of deformation and stress from squeezing and its possibility are necessary for establishment of a rational tunneling method. This study carried out three dimensional numerical analyses using a strain softening model in order to simulate the behaviour of squeezing and to estimate deformation and yield area around tunnels quantitatively. Numerical analyses were performed for 42 cases of various stress and strength conditions. As a result, the maximum tangential stress and strength of rock mass ratio could estimate plastic deformation and yield depth around tunnels and equations of relations between them were proposed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.1
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• pp.31-41
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• 2010

This paper presents both numerical and physical modeling approaches for the dilation and spalling of rock recognized as typical process of rock around an underground opening at depth. For physical approach, laboratory testing of rectangular beams using a synthetic rock was used to investigate the onset of dilation and spalling. The beams are axially compressed and subjected to 4-point bending to provide non-uniform compressive stresses which are similar to the maximum tangential stress distribution around circular openings. Discrete element numerical analyses using commercial code $PFC^{2D}$ (Particle Flow Code) were performed to evaluate the stress path at various locations in the beams. The findings from these approaches suggest that the onset of dilation in laboratory tests appears to be a good indicator for assessing the stress magnitudes required to initiate spalling.