• Geomechanics and Engineering
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• v.16 no.5
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• pp.513-525
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• 2018

Slope stability of sensitive clayey soils is particularly important when subjected to strength loss and deformation. Except for progressive failure, for most sensitive and insensitive slopes, it is important to review the feasibility of conventional analysis methods based on peak strength since peak strength governs slope stability before yielding. In this study, as a part of efforts to understand the behavior of sensitive clay slopes, a total of 12 centrifuge tests were performed for artificially sensitive and insensitive clay slopes using San Francisco Bay Mud (PI = 50) and Yolo Loam (PI = 10). In terms of slope stability, the results were analyzed using the updated instability factor ($N_I$). $N_I$ using equivalent unit weight to cause a failure is in reasonable agreement shown in the Taylor's chart ($N_I$ ~ 5.5). In terms of dynamic deformation, it is shown that two-way sliding is a more accurate approach than conventional one-way sliding. Two-way sliding may relate to diffused shear surfaces. The outcome of this study is contributable to analyzing stability and deformation of steep sensitive clay slopes.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.99-106
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• 2004

Although fly ash has possesses viable engineering properties, an overwhelming majority of fly ash from coal combustion is still placed in storage or disposal sites. This study was undertaken to investigate the physical and mechanical properties of clay-fly ash mixture and to furnish engineering data when fly ash utilized as engineering materials. This paper includes geotechnical properties of fly ash, clay-fly ash mixtures and results of compaction test, unconfined strength test, direct shear test, leaching test and stability analysis of clay-fly ash bank slope. If proper amount of fly ash was put in clay, the clay-fly ash mixture has an increase of unconfined strength and stability of bank slope.

• Journal of the Korean Society of Safety
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• v.36 no.5
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• pp.18-26
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• 2021

The effect of heavy construction equipment on the excavated slope is investigated by slope stability analysis. A mobile crane with 500 kN capacity is applied as a working load to the background surface of the excavated slope, in both sandy soil and clay, designed to guarantee the safety of slope stability. Major parameters such as the distance between the edge of the slope and the mobile crane, groundwater level, and ground plate size of the mobile crane are considered. Only 23.8% and 14.3% of the analysis models with sandy soil and clay excavated slope, respectively, satisfied the slope stability. By changing the slope of the sandy soil from 1:1.0 to 1:1.2, the number of analysis models securing slope stability increased from 23.8% to 40.5%. For the clay excavated slope, the analysis models securing slope stability increased from 14.3% to 42.9% by changing slope inclination from 1:0.8 to 1:1.2. In addition, it is found that the increase in the size of the ground plate of the mobile crane increases the analysis models that secure slope stability. Therefore, it is an effective way to relax the excavated slope's inclination angle and simultaneously increase the ground plate size to guarantee stability.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.507-511
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• 2009

This paper describes the performance design requirements of the slope and soft clay structures to confirm several contents of foundations systems to change existing design code to new one in the construction market. The concepts of performance design explain systematical needs for specific performance guidelines.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.185-196
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• 2010

Clay veins that occurred in a slope by hydrothermal alteration, can significantly affect its slope stability. The effect of clay veins on the slope stability was investigated by numerical modeling study. Various parameters such as cohesion, internal friction angle, orientation, groundwater level, rainfall intensity and duration, have been modelled. As shear strength increased, factor of safety increased. As groundwater level developed, factor of safety decreased. For the case of slip surface developed on interface, factor of safety was lower than that for case of slip surface developed on either weathered soil or clay vein. The effect of various soil types of the slope stability was also investigated by simulating seepage through the slopes with various soils. The groundwater level significantly increased on the slopes with silty and generic soils. For the slope with sandy soil, almost no change in groundwater level was observed due to rapid drainage.

• Tunnel and Underground Space
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• v.17 no.3 s.68
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• pp.175-185
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• 2007

When filling material such as clay is included along the discontinuity, it may cause instability on a slope even if the direction of discontinuity works in a positive way. In the study area, slope sliding occurred at the boundary between a clay filling material and weathered soil because the physical properties differ across the boundary; and this is very similar to the situation where foliation in a rock works as a weak zone during a structural behavior, causing an inter-layer slip. In most analysis, if there exists a clay filling material, a single discontinuity is assumed to perform analysis. In those cases, the discontinuity is modeled as a slip surface within clay. Therefore, the characteristics of the boundary are not considered in the analysis, so that ultimately the physical property of clay usually prevails. The result of evaluating the slope stability affected by clay filling material shows the significant difference in the safety level due to the strength parameter depending on the failure type of the discontinuity by a filling material.

• Geotechnical Engineering
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• v.4 no.4
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• pp.5-18
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• 1988

A series of CU triaxial compression tests were conducted to investigate the variation of -untrained shear strength of underconsolidated clay at different degrees of consolidation. The soil samples were artificially made by one-dimensional consolidation using soft Bangkok Clay. The test results showed that the undrained shear strength of clay parabolically increased convoking downward with increasing degrees of consolidation. However, all the measured shear strength were unanimously related to the effective stress. These experimental results were used in the numerical analysis. A finite element computer program was developed to investigate the stability of submarine .slope undergoing rapid deposition taking into account the variation in soil compressibility and permeability during the consolidation process. The relationships of degree of consolidation with time as a function of rate of deposition and angle of slope were established. A method of predicting the time of slope failure and the volume of moving mass of soil was also made.

• Mineral and Industry
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• v.29
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• pp.56-66
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• 2016

In Korea, where hydrothermal alteration zones are widely distributed, clay veins formed by hydrothermal alteration processes on natural slopes or artificial slopes can play an important role in the slope stability. When the surface water infiltrates the ground where the clay vein exists, the pore water pressure in the ground can be locally increased due to impermeable properties of clay minerals. Infiltration of the surface water induces the increase in the pore water pressure, which can cause erosion of the fine clay particles. The eroded clay particles flow and deposit in an area where the flow velocity is slowed down. Where clay minerals are deposited, ground water can leak due to an increase in local pore pressures, which can cause slope failure. In this paper, studies related to hydrothermal clay vein and landslide are introduced.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.848-857
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• 2008

In September 2007, the collapses of slopes and landslides are happened at Jeonlanamdo due to heavy rains accompanied with Typoon "Nari". The study area is the tunnel portal slope in new road construction site. This slope consists of pyroclastic rocks and has lots of faults. Particularly, the residual soils of the slope is deteriorated with yellowish mudstone layer as a results of chemical and physical weathering. This has a variety of swelling clay minerals and might be moved easily down at the gentle terrain. The inner factor of $\bigcirc\bigcirc$tunnel portal slope's collapse is the geological weak zone, the convergent topography, the inferiority of drainage and the heavy rain act on the failure as direct trigger.

• Tunnel and Underground Space
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• v.16 no.5 s.64
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• pp.368-376
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• 2006

After heavy rainfall, It was occurred massive plane failure along bedding plane of shale in the center of rock slope. It was observed filling material and trace of underground water leakage around of the slope. We tried to find the cause for slope failure, and the result of examination showed that primary factors of the failure were low shear strength of clay filling material and water pressure formed within tension crack existed in the top of the slope. In this research, in order to examine the features of shear strength of filled rock joint, shear test of filled rock joint was conducted using of artificial filling material such as sand and clay..Also we made an investigation into the characteristics of shear strength with different thickness of filling materials.