• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.699-714
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• 2022

The objective of this study is to suggest a safe and economical pillar reinforcement method when very near-twin tunnels with a minimum interval of 1 m passes through a soft zone such as weathered soil or weathered rock. A standard cross-sectional view of a two-lane road tunnel was applied to suggest a pillar reinforcement method for the very near-twin tunnels. The thickness of the pillar was 1 m. The ground condition around the tunnel was weathered soil or weathered rock. There were four reinforcement methods for pillar stability evaluation. These were rock bolt reinforcement, pre-stressed steel strand reinforcement, horizontal steel pipe grouting reinforcement, horizontal steel pipe grouting + prestressed steel strand reinforcement. When the ground condition was weathered soil, only the pillar reinforced the horizontal steel pipe grouting + prestressed steel strand did not failed. When the ground condition was weathered rock, there were no failure of the pillar reinforced the horizontal steel pipe grouting or the horizontal steel pipe grouting + prestressed steel strand. It is considered that the horizontal steel pipe grouting reinforcement played a role in increasing the stability of the upper part of the pillar by supporting the upper load applied to the upper part of the pillar.

• Geomechanics and Engineering
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• v.16 no.1
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• pp.105-112
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• 2018

This paper presents results of a compressive investigation conducted on weathered soil stabilized with ground bottom ash (GBA) and red mud (RM). The effects of water/binder ratio, RM/GBA ratio, chemical activator (NaOH and $Na_2SiO_3$) and curing time on unconfined compressive strength of stabilized soils were examined. The results show that the water/binder ratio of 1.2 is optimum ratio at which the stabilized soils have the maximum compressive strength. For 28 days of curing, the compressive strength of soils stabilized with alkali-activated GBA and RM varies between 1.5 MPa and 4.1 MPa. The addition of GBA, RM and chemical activators enhanced strength development and the rate of strength improvement was more significant at the later age than at the early age. The potential environmental impacts of stabilized soils were also assessed. The chemical property changes of leachate from stabilized soils were analyzed in terms of pH and concentrations of hazardous elements. The observation revealed that the soil mixture with ground bottom ash and red mud proved environmentally safe.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.831-838
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• 2004

To study on mechanical characteristics of weathered granite masses are difficult because of undisturbanced sampling and in-situ test. Generally, pressuremeter test is widely used to investigate the behavior of weathered rock masses. However, it has many problems to get a limit pressure because of cavity collapse, membrane damage, ete. This study aims to evaluate the mechanical characteristics of weathered granite masses using in-situ pressuremeter test and numerical analysis depending on the ratio of length and diameter of the membrane(L/D=5, 8, 10, 15, 20). Test results and data are shown that strength parameters are reduced exponentially varing weathering degree, and numerical analysis results are approximately coincided with the test results. And the ratio of length and diameter of the membrane arc not affected the parameters such as modulus of pressuremeter, shear modulus, etc. But limit pressure is increased decreasing membrane length based on numerical analysis. On the other hand, increasing the membrane length, yield pressure is decreased and plastic radius is increased in the case of same weathering degree.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.247-254
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• 2000

In this study, the reinforcing effect of micropile for weathered rock is analysed by laboratory model tests. Especially, the effect of the number, the surface roughness, and length of micropile are focused. The results of tests are as follows: $\circled1$ The deformation modulus of reinforced ground is less than equivalent deformation modulus, and $\circled2$ Increasing effect of unconfined compressive strength is not large as times as increasing the number of micropile.

• Journal of the Korean GEO-environmental Society
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• v.7 no.2
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• pp.5-14
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• 2006

It has been reported that the failure of a slope in weathered soils or rocks induced by intensive rainfall occurs mainly within 2.0m below the ground surface, and that the effect of rainfall on the rise of the ground water level is not significant if the ground water level inside the slope is not so high before rainfall. Most slopes in Korea, however, have been examined to rather fail at the deeper part since they are usually designed on the basis of assumption that the ground water level rises up to the surface when raining. In this study, the rise of ground water level and slope stability were examined in order to verify the appropriateness of the current ground water level condition that has a significant effect on slope stability using the average daily rainfall in Seoul for the last 30 years. The result showed that the ground water level appears to rise up to 6.0~41.0% of the slope height respectively, and therefore the currently applied condition of ground water level may be somewhat overestimated.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.6
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• pp.106-114
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• 2000

In order to evaluate the shear characteristics of undisturbed weathered granite soil which is a typical residual soil in Korea, the mechanical properties are first investigated and discussed by carrying out a series of direct shear test and then dilatancy correction is performed by using Taylor’s correction equation. In this study, specimens are sampled at Pungam(-3, -8, -13m below ground surface), Kwangju and Iksan(-5m below ground surface), Jeonbuk. The test results are summarized as follows: 1) Mohr-Coulomb failure criterion is not linear under the low confining pressure. 2) The value of cohesion is smaller than usually determined value in low pressure region. 3) The value of strength parameter c and ø which are corrected by Taylor’s correction equation is a little bit small.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.2
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• pp.70-79
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• 1999

The lower ground of structure, in which the strip loads, such as earth dams and embankments , are signiificantly working on , is required to be interpreted as a state of plane strain where the strain of intermediated principal stress direction is put '0' . The plane strain state is frquently observed in actural soil engineering case. For those case, drained stress-strain and strength behavior of Iksan weathered granite soil prepared in cubical specimens with cross-anisotropic fabric was studied by conventional triaxial compression, plane strain and cubial triaxial tests with independent control of the three principal stress. All specimens were loaded under conditions of principl stress directions fixed and aligned with the directions of the material axes. As a result of research , when a ground condition is analyzed under plane strain state, the shear strength obtained from the conventional triaxial compression test can be understimated.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.109-117
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• 2006

This study is an numerical study of predicting the behavior of anchor embedded in weathered rocks, subjected to uplift loads, about ultimate pullout capacity and the failure mechanism. Factors influencing the behavior of anchors were investigated by reviewing the data about in-situ anchor tests performing numerical modelling with changing the bondage length of anchor, diameter of anchor body and diameter of tenden, and by Correlations between those factors were evaluated to apply them to predict the behavior of anchors. As results of numerical analysis, a linear relationship between bondage length, diameter of anchor body and diameter of tenden with ultimate pullout capacity was obtained on the one hand, from the result of numerical analysis changing the Young's modulus of weathered rock, this parameter was found to inflence to load-displacement and ultimate pullout capacity within the range of 10%, which was mot so significant to affect.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.06b
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• pp.17-34
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• 1998

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.517-523
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• 2007

Geophysical surveys(seismic refraction, electrical resistivity, and ground penetrating radar) were performed to delineate the weathering zone associated with vadose water in Chojeong area and investigate the fault related fracture zones. On the basis of seismic velocity structures, weathering layer for the southwestern part is interpreted to be deeper than for the northeastern part. The depth to bedrock(i.e., thickness of weathered zone) from seismic refraction data attempted to be correlated with drill-core data and groundwater level. As for the investigation of geological discontinuities such as fault related fracture zone, seismic refraction, electrical resistivity, and ground penetrating data are compositely employed in terms of velocity and resistivity structures for mapping of surface boundary of the discontinuities up to shallow depth. Surface boundaries of fracture zone are well indicated in seismic velocity and electrical resistivity structures. Accurate estimation of weathered zone and fracture zone can be successfully available for mapping of attitude of vadose water layer.