• Journal of the Korean GEO-environmental Society
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• v.11 no.12
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• pp.57-62
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• 2010

In this study, the effect of different silt contents on the shear characteristics of silty sands was evaluated. Two series of triaxial compression tests were performed on the cylindrical specimens of compacted Nakdong river sand with 10% and 30% silt contents under unconsolidated undrained condition. All identical specimens were prepared to compact with same initial water content for five layers and saturated using control panel and then sheared under initial effective confining pressure, 100 to 400kPa. All specimens exhibited a strain softening tendency after failure in stress-strain curves and deviator stresses of specimens with 10% silt content were greater than those of specimens with 30% silt content. Pore water pressures of specimens with 10% silt content were observed negative(i.e. swelling) due to increasing void ratio after failure but those of specimens with 30% silt content were shown only positive. The behavior of compacted cylindrical specimens with low silt content was more dilative than that of high silt content. Peak deviator stresses decreased as increasing silt content and peak pore water pressures increased as increasing silt content.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.151-153
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• 1995

Residual strain of artery is studied. There has been experimental evidence that residual strain exists in artery. When ring of artery is longitudinally cut, it is opened. Since strain has been determined without considering residual strain, the existence of residual strain is meaningful in mechanics of arterial wall. Intimal strain concentration is considered to be reduced with both account of residual strain and strain determined by loading. However, it is lack of experimental research. Therefore, this study experimentally attempts to quantify the effect of residual strain on circumferential strain which is determined under the assumption of zero strain with zero pressure.

• Journal of the Korean GEO-environmental Society
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• v.14 no.2
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• pp.51-55
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• 2013

Among various construction methods, deep soil stabilization by chemical method have been widely used in order to improve soft ground. Dynamic variables using ground(such as sand, weathered granite soil and rock) -structure interaction design affected by dynamic load and cyclic load were studied a lot. However, there is something yet to learn about earthquake resistant design regarding reinforced ground by grout. Therefore, in this study using RC test, the correlation between shear strain and shear modulus with change of water content and injection rate in normal portland cement and clay was compared and analyzed by using Ramberg-Osgood model normalization As the result, dynamic coefficient was considerably affected by water content and grout injection rate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6C
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• pp.239-247
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• 2012

Some methods were proposed to predict lateral flow due to embankments for road constructions on soft grounds, in which vertical drains were placed. In order to investigate the prediction methods of lateral flow, 200 field monitoring data for embankments in thirteen road construction sites at western and southern coastal areas of the Korean Peninsula were analyzed. For analyzing the relationship between the safety factor of embankment slope and the horizontal displacement in soft grounds where horizontal drain mats were placed, it was reliable to apply the maximum horizontal displacement in soft ground instead of the horizontal displacement at ground surface. The maximum horizontal displacement was developed less than 50mm in fields where the safety factor of slope was more than 1.4, while the one was developed more than 100mm in fields where the safety factor of slope was less than 1.2. In safe fields where the maximum horizontal displacement were developed within 50mm, lateral flow would not happen since shear deformation was not appeared. On the other hand, shear failure would happen in the fields where the maximum horizontal displacement were developed more than 100mm. In such fields, embankments might be continued after some appropriate countermeasures should be prepared. Safe embankments can be performed on soft grounds, in which the stability number is less than 3.0 and the safety factor for bearing is more than 1.7. However, if the stability number is more than 4.3 and the safety factor for bearing is less than 1.2, shear deformation would begin and even shear failure would happen.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.3
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• pp.11-20
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• 2008

In this paper, the characteristics of low hardness high damping rubber bearings(HDRB) were studied through various prototype tests. The low hardness HDRB were tested to evaluate vertical stiffness, shear stiffness, equivalent damping ratio, various dependencies of shear properties, ultimate shear properties and other factors. The prototype test was performed according to the specifications of ISO 22762-1, and evaluated according to the specifications of ISO 22762-3. The results of the prototype test showed that shear strain and temperature were the factors that most greatly influenced shear stiffness, and that compressive stress was the factor that most greatly influenced the equivalent damping ratio. The frequency dependence test of shear properties showed that two general tendencies of frequency dependence could be observed. At frequencies over 0.1Hz, the changes in shear properties were small. However, at frequencies under 0.1Hz, the changes in shear properties rapidly decreased. The creep test and the ultimate shear test were also performed, and both of them satisfied the requirements of ISO 22762-3.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.2 s.17
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• pp.57-63
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• 2005

In case of general structures, it has been known that the strain amplitude band experienced by the base in a state of service load is less than 1% and most of the base show low, strain amplitude behavior less than 0.01%. In this study examining the influence affected to dynamic behavior in a condition of the low strain amplitude of unsaturated decomposed granite soils, the resonant column test, using some samples in Su-won area, has been performed for each degree of saturation resulted from different void ratios and confined stress. It is found out that the minimum value of the damping ratio occurred in roughly $17{\sim}18%$ according to void ratios regardless of confined pressure in the same manner with the case of the maximum shear elastic modulus; and it is estimated that for the influence of surface tension in the optimum degree of saturation, the damping ratio appears to be least.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.83-92
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• 1987

Fatigue fracture of reinforced concrete structures are characterized by considerably larger strains and microcracking as compared to fracture of R.C. structures under static loading. The strain of stirrup is increased suddenly by the occuring of inclined crack and the average strain ${\epsilon}_{\omega}$ of all stirrups in a structure at maximum load increase approximately in proportion to log N. The structures critical in longitudinal reinforcement seemed to have an endurance limit of 60~70 percent of static ultimate strengths for 1,000,000 cycles. In this test, the average fatigue strength at 1,000,000 cycles for all structures tested was approximately 65 percent of the static ultimate strength.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.1
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• pp.21-30
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• 2006

In case of an urban tunnel, the displacement of ground base controls the tunnel design because it is built on shallow and unconsolidated ground many times. There are more insufficiency to describe the ground movement which coincides in the measured result of the situ because the design of an urban tunnel is dependent on the method of numerical analysis used to the existing elastic and elasto-plastic models. We studied about the predict ion for the ground movement of a shallow tunnel in unconsolidated ground, mechanism of collapse, and settlement. Also this paper shows comparison with the existing elastic and elasto-plastic model using the unlinear analysis of the strain-softening model. We can model the real ground movement as the increasement of ground surface inclination or occurrence of shear band by using strain-softening model for the result of ground movement of an urban NATM tunnel.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.87-102
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• 1991

It has been reported that the failure of Carsington Dam in Eng1and occured due to the existence of a thin yellow clay layer which was not identified during the design work, and due to pre-existing shears of the clay layer. The slope stability analyses during the design work, which utilized traditional circular arc type failure method and neglected the existence of the clay layer, showed a safety factor of 1.4. However, the post-failure analyses which utilized translational failure mode considering the clay layer and the pre-existing shear deformation revealed the reduction of safety factor to unity. The post-failure analysis assumed 10。 inclination of the horizontal forces onto each slice based on the results of finite element analyses. In this paper, Bishop's simplified method, Janbu method, and Morgenstern-Price method were used for the comparison of both circular and translational failure analysis methods. The effects of the pre-existing shears and subsquent movement were also considered by varying the soil strength parameters and the pore pressure ratio according to the given soi1 parameters. The results showed factor of safefy 1.387 by Bishop's simplified method(STABL) which assumed circular arc failure surface and disregarding yellow clay layer and pre-failure material properties. Also the results showed factor of safety 1.093 by Janbu method(STABL) and 0.969 by Morgenstern-Price method(MALE) which assumed wedge failure surface and considerd yellow clay layer using post failure material properties. In addition, dam behavior was simulated by Cam-Clay model FEM program. The effects of pore pressure changes with loading and consolidation, and strength reduction near or at failure were also considered based on properly assumed stress-strain relationship and pore pressure characteristics. The results showed that the failure was initiated at the yellow clay layer and propagated through other zones by showing that stress and displacement were concentrated at the yel1ow clay layer.

• Journal of the Korean Geotechnical Society
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• v.23 no.2
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• pp.35-45
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• 2007

In this research, artificially cemented sand which is made of a few portland cement and Nak-Dong river sand was researched closely. For providing the fundamental data which is needed in design and analysis of levee material, the shear behavior of cemented sands was investigated by drained triaxial test, and analyzed in accordance with the increase of cement content. The peak strength and elasitc modulus increased and dilation of cemented sand was restricted by the cementation, but after breakage of the cementation, dilation increased, cohesion intercetpt and friction angle increased with the increase of cement content and strain softening behavior appeared in stress-strain curve.