• The Journal of Engineering Geology
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• v.7 no.3
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• pp.161-171
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• 1997

The exact information on geological structures and characteristics of the subsurface must be acquired to secure quality and safety of constructions. GPR technique, one of the most updated geophysical methods, is known for its applicability to shallow-depth underground surveys. The purpose of this study is to examine the usefulness of GPR method in constructions for detailed subsurface investigations, especially detecting the boundary between basement rock and its overburden. To find appropriate depths of the geological boundaries, it is necessary to obtain velocity of electromagnetic wave propagating into the ground. Wave velocity 0.096 m/ns estimated from velocity analysis using CMP gathers is used for depth conversion from time section. The depths of geological boundaries from GPR profiles are very well correlated with boring data. In addition, GPR survey has found some undulations of the geological boundaries due to weathering, which cannot be provided by conventional coring approaches.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.295-301
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• 2001

Geological and geophysical surveys were performed to examined the cause of the rock-mass slide occurred at the opening site of the Wanglim tunnel of the Seoul-Pusan High Speed Railway. The results of geophygical survey and geometrical analysis for the geological structures indicate that the rock-mass slide was triggered by the heavy rainfall which increases the groundwater level and results in high pore pressure in the N60$^{\circ}$ E-trending major fractured zone of the slope, and that the foliation dipping toward the vertical open face of the slope acted as a main sliding plane during movement.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.497-514
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• 2020

This study investigated the causes of large-scale ground subsidence in the upper part of mining cavities of the Samdo limestone mine, Samcheok city, Gangwondo, Korea. Geological and electrical resistivity surveys were undertaken on the collapsed slope of the mountain and in the mine tunnel where subsidence occurred, with geotechnical evaluations and numerical analysis. It is concluded that wide mining cavities, with irregular pillars in unstable rock masses hosting discontinuities, weathered over time, resulting in subsidence occurring along a fault plane due to increasing ground stress.

• The Journal of Engineering Geology
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• v.31 no.2
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• pp.179-186
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• 2021

Malpasset Dam, located in France, is of great importance in the field of civil and geotechnical engineering as it was the first arch dam that totally collapsed in 1959. A three-dimensional model of the dam was reconstructed using close-range photogrammetry technique. The orientations of foliation developed in the bedrock and the collapse surface were measured. Moreover, both model and measurement results showed high precision. The study result can be used in future studies such as collapse simulation analysis and geotechnical investigations.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.69-81
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• 2008

Landslide researches are divided to a method of interrelationship for various factors, method of predicting landslide possibility, and method of estimating landslide risk which are occurring landslides in the natural slope. Most of landslides occurred in natural slope are caused by a heavy rainfall in summer season. Weathered soil layer located in upper side of rock mass was occurred. As well as, they are announced to have an influence to geometry, geology, soil characteristics, and precipitation in the natural slope. In order to investigate and interpret the variety of landslides from field investigation to risk analysis, landslide analysis process due to geotechnical and geological opinions are systematically demanded. In this research, the study area is located in Macheon area, Gyeongsangnam-do and performed the landslide investigation. From the results of landslide investigation and analysis, optimized standard model based on natural landslide is proposed to high technical method of landslide investigation and interpretation.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.147-159
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• 2007

단층의 공학적 의미와 분류방법을 살펴보고 토목구조물의 설계 및 시공을 위하여 조사단계에서 단층에 대한 분포 및 공학적 특성을 파악하기 위한 각종 물리탐사, 현장시험, 실내시험 사례를 검토하였다. 단층의 분포특성 조사 사례를 통하여 지표지질조사, 시추조사, 물리탐사 결과들의 상호 관계를 살펴보고, 단층 및 주변 상태에 따라 적정한 탐사 및 조사 방법을 검토하였다. 그리고 단층의 공학적 특성 평가를 위한 현장 및 실내시험 방법을 고찰하고, 단층의 점착력, 마찰각 등과 같은 물성치의 산정 사례들을 수집하여 분석하였다.

• The Journal of Engineering Geology
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• v.23 no.1
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• pp.67-77
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• 2013

We conducted a Tunnel Seismic Prediction (TSP) survey in a spillway tunnel at Juam Dam to predict the locations of major discontinuities ahead of the tunnel face. We compared the results of the TSP survey with those from pre-construction inspections (including a surface resistivity survey and borehole investigations) as well as with direct tunnel-face mapping during excavation. The TSP method predicted the locations of major fracture zones that were unnoticed in the pre-construction inspections. The reinforcement patterns planned on the basis of pre-construction inspections were changed on the basis of the TSP results. The results demonstrate that TSP surveys are a cost-effective and reliably accurate method of predicting the locations of fracture zones. Although the TSP method has some limitations, these results suggest that the method is generally useful for predicting geological conditions prior to tunnel face construction.

• Proceedings of the KSEG Conference
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• 2002.04a
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• pp.201-210
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• 2002

서울시 북동부의 서울화강암에 대한 암반 공학적 특성 중 터널과 도로 건설시 중요하게 취급되는 절리의 방향성, 절리간격, 절리밀도, 암석의 일축압축강도, 그리고 RQD 값을 수락산과 불암산지역으로 구분하여 비교, 분석하였다. 이 중 절리의 방향성, 절리간격과 절리밀도는 선조사법, 원형조사법, 그리고 면적조사법을 이용하여 야외에서 직접 측정하였다. 암석의 일축압축강도와 RQD의 측정은 시추코아의 표본이 필요하지만 이번 연구에서는 간단히 응용할 수 있는 대비공식을 이용하여 계산하였다. 측정된 대표적인 절리의 방향성은 두 지역에서 모두 3조의 방향성이 나타났으며 즉 2조의 수직정방절리와 저각으로 경사하는 1조의 판상절리로 판명되었으며 두 지역에서 서로 유사한 방향성을 갖는다. 측정된 절리밀도는 0.039-0.066/cm이었으며, 평균절리길이는 1.30-4.52m, 그리고 평균절리간격은 10.3cm에서 최대 59.6cm로 측정된 절리의 방향에 따라 변화가 심하다 또한 슈미트 해머 타격값에 근거한 절리면의 일축압축강도는 217 MPa에서 335 MPa로 매우 강한 암체였으며, 평균절리간격에 기초하여 계산된 이론적 RQD 값은 73.1-98.7%의 값을 갖는 것으로 나타났다.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.101-113
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• 2001

Structural and geological engineering properties of the rock mass distributed in the Yokmang mountain area were investigated to detenninc the usable cut-out volume and quarrying efficiency. The study area is located in the southern tip of the Yangsan fault system which controls the geological structure of the Kvungsang basin. As a result, the study area is mainly composed of andesicic. rhyolitic. and granitic rocks of the Cretaceous Kyungsang Supergroup and a series of right-handed strike-slip faults is developed along NNE-SSW direction. These regional faults significantly affect the spatial and meclwnical characteristics of joints such as spacing, frequency, and compressive strength. The joint frequency is highest along the fault zones and decreases toward the remote region. Based on the geological information obtained from the field survey, the detailed structure of the Yokmang mountain was analyzed and the volume of the rock mass was assessed. Considering the minimum rock block size required for the construction of a coastal dumping site, potential cut-out volume is then estimated to be 4,018,000m$^3$ the volume % of which is 48% of Yokmang mountain including the soil and weathered rock and 61% of the unweathered rock mass.

• The Journal of Engineering Geology
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• v.15 no.1
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• pp.41-55
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• 2005

This research is aimed at investigating the ground characterization of the Cheongju granite area using the geophysical methods. Test site was chosen from the building site in Chungbuk University, Chongju, Chungbuk province. Furthermore, geophysical methods are employed on the outcrops in the east to map the distribution of fault and intrusion and reveal the degree of weathering. The subsurface structure mapped from seismic re-fraction survey mainly consists of two units of weathered soil and rock. Threshold of the units were determined on the basis of seismic velocity of 800 m/s, supported from the standard classification table. From the results of standard penetrating test(SPT), these units are found to show medium-high and high density, respectively. Weathering soil is subdivided in unsaturated layer and saturated layer with thresholds of seismic velocity (500 m/s) and resistivity (200 ohm-m). In particular, unsaturated layer is again classified into dry and wet portions using the GPR section. The boundary between unsaturated and saturated weathering soils corresponds to the groundwater table at depth of approximately 5～6.2 m, which is well correlated with the one from drill-core data. However, bedrock is not delineated by geophysical methods. In the GPR section, fault and intrusion observed on the outcrop are revealed not to extend to the building site. With respect to weathering degree, the outcrop characterized by low resistivity and velocity corresponds to the grade of 'completely weathered' from the geotechnical investigations.