• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.213-227
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• 2002

절토사면의 붕괴원인은 토질 및 지질조건, 지형, 강우, 지하수 및 지표수, 사면형상, 굴착 및 발파와 같은 인위적인 조건, 사면보호공 등과 같이 다양한 영향이 있을 수 있으나 가장 많은 영향을 주는 원인으로 토질 및 지질적인 조건이라고 할 수 있다. 본 논문은 이러한 지질조건에서 붕괴가 발생될 경우의 활동면에 대한 전단강도 추정하는 방법에 있어 역해석법에 의한 활동면의 전단강도 추정을 연구하였다 연구결과 붕괴된 사면에서 화성암은 마찰각 20$^{\circ}$~30$^{\circ}$, 점착력 0~2t/$m^2$의 범위를 가지며 퇴적암에서는 마찰각 $10^{\circ}$~17$^{\circ}$, 점착력 0~2.5t/$m^2$의 범위, 변성암에서는 마찰각 $10^{\circ}$~40$^{\circ}$, 점착력 0~4.0t/$m^2$의 범위가 우세한 것으로 나타났다. 그리고 지질구별 구분에 의하면, 절리에 의해 붕괴가 발생된 경우에는 마찰각 30$^{\circ}$~40$^{\circ}$, 점착력 0~3.5t/$m^2$, 엽리면은 마찰각 30$^{\circ}$~35$^{\circ}$, 점착력 0.5~3.0t/$m^2$, 단층면은 마찰각 11$^{\circ}$~38$^{\circ}$, 점착력 0~3.0t/$m^2$, 층리면은 마찰각 $10^{\circ}$~17$^{\circ}$, 점착력 0~2.5t/$m^2$ 정도의 범위를 갖는 것으로 나타났다.

• Journal of the Korean Geotechnical Society
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• v.31 no.1
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• pp.15-24
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• 2015

This paper presents the results of a reduced-scale physical model investigation into the effect of drilling fluid with different mix designs for bore hole collapse prevention. The bore hole collapse prevention mechanism for the bentonite based drilling fluid was first discussed together with the effect of conditioning with different additives on engineering characteristics of bentonite based drilling fluid. Reduced-scale model tests were then carried out considering field procedures for cases with a decomposed granitic soil with 20% fines and a sand with various drilling fluids with different mix designs. The results indicated that the addition of polymer to the bentonite based drilling fluid decreases the amount of drilling fluid injected, the drilling fluid infiltration thickness and increases the final depth of excavation. Also revealed is that the effect of polymer on the performance of drilling fluid is more pronounced in the decomposed granite soil with 20% fines than the sand. Practical implications of the findings from this study are discussed in great detail.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.485-496
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• 2020

The characteristics of volumetric water content changes in soil slopes were studied here in an effort to identify the signs of heavy rain causing shallow slope failure. Volumetric water contents in cases with and without shallow failure were measured in flume and test-bed experiments. Measurement data from 282 experiments of both types revealed that the volumetric water content gradient in shallow failure events ranged from 0.072 to 0.309. In non-failure cases, the range was 0.01~0.32. Therefore, this one specific value cannot predict shallow slope failure. However, as the volumetric water content gradient increased, there was a clear tendency to shallow failure. By using this trend, criteria for four warning levels are suggested.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.409-425
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• 2013

This study presents a prediction of a time-series of the area inundated by effluent from Heavenly Lake caused by ground behavior prior to a volcanic eruption. A GIS-based hydrological algorithm that considers the multi-flow direction of effluent, the absorption and storage capacity of the ground soil, the storage volume of the basin or the depression terrain, was developed. To analyze the propagation pattern, four hypothetical collapse zones on the cheonji ground were set, considering the topographical characteristics and distributions of volcanic rocks at Mt. Baekdu. The results indicate that at 3 hours after collapse, for both scenarios 1 and 2 (collapses of the entire/southern boundary of cheonji), a flood hazard exists for villages in China, but not for those on the North Korean side of the mountain, due to the topographical characteristics of Mt. Baekdu. It is predicted that villages in both North Korea and China would be significantly damaged by flood inundation at 3 hours elapsed time for both scenarios 3 and 4 (collapses on the southern boundary of cheonji and on the southeastern-peak area).

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.83-93
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• 2010

The purpose of this study is to present emergency rehabilitation, cause and the countermeasure of reinforcement about reinforced retaining wall and the slope collapse of the phyllite ground. The study area is broken easily because this area has rock mass discontinuity such as stratification, foliation, joint and fold. And this area consists of the ground where it happens easily to the failure of structure like reinforced retaining wall because of the phyllite ground sensitive to weathering. Counterweight fill in front of reinforced retaining wall was performed as emergency rehabilitation about displacement of reinforced retaining wall and the failure at the rear of slope on phyllite ground. After that, additional displacement didn't occur. Boring and geophysical exploration were launched to present emergency rehabilitation and develop the long-term method of reinforcement. This could grasp anticipated range of the failure section and identify internal and external factors of the cause of the slope collapse. Several methods of reinforcement were suggested by conducting the numerical analysis. When conducting design and construction of major structures at the ground which has complex discontinuities, the precise site investigation should be conducted. During construction, immediate action for over-displacement should be taken by performing the periodic measurement.

• The Journal of Engineering Geology
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• v.14 no.1
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• pp.71-80
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• 2004

The failure of cut slopes frequently occurs particularly during the thawing season and the rain season in summer. This study interpreted data collected from site to which a real-monitoring system was applied in order to analyze the causes of ground behaviors and to forecast future slope failure. As for research methods, this study analyzed the size and mechanism of failure by integrating the results of field surveys and measurements. Furthermore, it analyzed data transmitted by the monitoring system installed in the a result, three times of ground displacement occurred as well as a number of partial tension cracks. The cut slope composed of sandstone and siltstone started its initial behavior as a result of torrential downpour and the loss of support of the substructure. For quantitative analysis of the characteristics of ground behavior, this study measured 5 lateral lines. According to the result of the measurement, displacement happened little in the section to which countermeasure had been applied, but displacement of maximum 400mm happened in the section to which countermeasure had not bee applied. The analysis of data on displacement and rainfall suggested a close relationship between ground behavior and rainfall. According to the result of stability interpretation along with the change of ground saturation, stability rate appeared to be less than 1.0 when ground saturation is over 55%. Although the current trend of ground behavior is at a stable stage falling within the range of tolerance, it is considered necessary to continue monitoring and data analysis because ground displacement is highly possible with the change of temperature during the winter.

• Journal of the Korea Construction Safety Engineering Association
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• s.45
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• pp.60-70
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• 2008

Mechanized tunnelling by TBMs has been extensively adopted for last two decades. Nevertheless, only few case histories have been reported. Unlike NATM tunnels, the case histories of the weak zone have been seldom reported for the mechanized tunnelling, even in the other countries. In this study, a collapse of TBM tunnel occurred in the severely altered weak rock zones between volcaniclastic rocks and granitic rocks was briefly described. A systematic geotechnical investigation, which was performed to examine the cause of the collapse, was carried out at the site and then characteristics of the rocks in the zones were evaluated. Moreover, This study propose a guide line of estimateing the possibility of collapse in TBM tunnels through comparing experimental results with surveying results of general rocks.

• Journal of the Korean GEO-environmental Society
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• v.17 no.3
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• pp.27-35
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• 2016

Even if the various data analyzing methods were suggested to examine the measured slope behaviors, it is difficult to find methods or procedures for connecting the analyzed results of slope stability and measured slope data. This research suggests the analyzing methods combing the stability analysis and measured data based on progressive failure of slope. Slope failure analysis by time degradation were calculated by strength parameters composed of strength reduction coefficients, also which were compared to the measured data according to the variations of safety factor and displacement of slopes. The accumulated displacement curve were shown as 3rd degree polynomials by suggested procedures, which was the same as before researches. The reverse displacement velocity curves were shown as linear function for prediction of brittle slope failures, also they were shown as 3rd degree polynomials for ductile slope failures, which were the same as the suggested equation by Fukuzono (1985) and they were very similar behaviors to the in-situ failure cases.

• Journal of Korean Society of societal Security
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• v.2 no.4
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• pp.75-81
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• 2009

This paper presents the geotechnical characteristics of tunnel co \l apse based on the case studies. For domestic cases, most collapses are likely to happen along the weakest zone of shear strength due to the change of stresses induced by excavation specially when soft or weathered rock exist in front of a tunnel. In other words, the collapse of a tunnel occurs along the highly weathered fractured zone due to blasting and excavation. In Europe, collapses have been occurred by one joint group even though the ground is relatively fresh and for the rocks of which RQD is over 50%. In addition, the amount of ground water flow does not seem to be seriously affected by the RQD range.

• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.57-66
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• 2016

In this study, to prevent possible collapse caused by hydraulic or mechanical instability, liquid nitrogen injection method is developed and implemented at the tip of drilling auger of steel pipe propulsion tunneling. In this study, 1/5-scale model auger and sand chamber were manufactured. The prototype diameter of steel pile (or casing) is assumed about 1,000 mm. For the frictional sandy soils and plastic weathered soils, liquid nitrogen injection methods were tested varying water contents of the soils. For the induced hydraulic instability, the ground near the drilling auger was frozen within approximately 5 minutes preventing mechanical collapse and water infiltration. Securing stability of steel pile propulsion tunneling using liquid nitrogen was much more effective for which the water content of the soil somewhat exceeds the optimum water content.