• Journal of the Korean Geotechnical Society
• /
• v.19 no.6
• /
• pp.151-160
• /
• 2003

The stability of the designed rock slope is analysed based on two kinds of shear strength model. Besides the deterministic analysis, a probabilistic approach on Monte Carlo simulation is proposed to deal with the uncertain characteristics of the discontinuity and the results obtained from two models are compared to each other. To carry out the research of characteristics of the discontinuity, BIPS, DOM Scanline survey data and direct shear test data are used, and chi-square test is used for determining the probability distribution function. The rock slope is evaluated to be stable in the deterministic analysis, but in the probabilistic analysis, the probability of failure is more than 5%, so, it is considered that the rock slope is unstable. In the shear strength models, the probability of the failure based on the Mohr-Coulomb model(linear model) is higher than that of the Barton model. It is supported by the fact that the Mohr-Coulomb model is more sensitive to block size than the Barton model. In fact, there is no reliable way to estimate the unit cohesion of the Mohr-Coulomb model except f3r back analysis and in the case of small block failure in the slope, Mohr-Coulomb model may excessively evaluate the factor of the safety. So, the Barton model of which parameters are easily acquired using the geological survey is more reasonable for the stability of the studied slope. Also, the selection of the proper shear strength model is an important factor for slope failure analysis.

• Tunnel and Underground Space
• /
• v.15 no.1 s.54
• /
• pp.28-38
• /
• 2005

According to the recent development of measurement system utilizing one or a set of boreholes, visualization of the explored underground became to be a major issue. It induced even the introduction of monitoring apparatuses on the borehole wall with multi-function tool, but the usage of these was often limited by where is unfavorable rock condition and a few of engineers can approach. And so, a portable type of borehole camera with only the essential function has been investigated and a few of commercial models about this is recently being applied into the field condition. This paper was based on the monitoring results obtained using a commercial model by Dr. Nakagawa. Discontinuities in rock mass were the topic for the visualization, and it was studied how can visualize their three dimensional distribution and what a numerical formulation is needed and how to understand the visualization result. The numerical formulation was based on the geometric correlation between the dip direction / dip of discontinuous plane and the trend / plunge of borehole, a set of the equation of a plane was induced. As field application of this into two places, it is found that the above visualization methodology will be especially an useful geotechlical tool for analyzing the local distribution of discontinuities.

• Economic and Environmental Geology
• /
• v.33 no.4
• /
• pp.295-307
• /
• 2000

Probabilistic analysis is a powerful method to quantify variability and uncertainty common in engineering geology fields. In rock slope engineering, the uncertainty and variation may be in the form of scatter in orientations and geometries of discontinuities, and also test results. However, in the deterministic analysis, the factor of safety which is used to ensure stability of rock slopes, is based on the fixed representative values for each parameter without a consideration of the scattering in data. For comparison, in the probabilistic analysis, these discontinuity parameters are considered as random variables, and therefore, the reliability and probability theories are utilized to evaluate the possibility of slope failure. Therefore, in the probabilistic analysis, the factor of safety is considered as a random variable and replaced by the probability of failure to measure the level of slope stability. In this study, the stochastic properties of discontinuity parameters are evaluated and the stability of rock slope is analyzed based on the random properties of discontinuity parameters. Then, the results between the deterministic analysis and the probabilistic analysis are compared and the differences between the two analysis methods are explained.

• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 1998.11a
• /
• pp.303-308
• /
• 1998

암반을 대상으로 하는 건설공사는 많은 시간과 비용, 설계, 시공, 안전상에 많은 문제점을 일으키고 있다. 이러한 암반들은 흡수, 풍화 등에 기인하여 안정성이 약화되어 낙석, 산사태, 붕괴 등의 위험을 안고 있으며 이러한 현상은 우기, 해빙기에 두드러지게 나타나고 있다 비균질, 비등방성의 역학적 성질을 지닌 암석은 변형 거동을 완벽하게 예측하지는 못하고 있는 실정으로 이러한 거동은 암석의 종류와 구성 광물, 내부 불연속면의 상태, 응력 조건과 온도, 습도의 함수비등과 같은 다양한 요소에 의해 영향을 받으며, 이러한 경향은 퇴적암의 경우 두드러지게 나타나고 있다. (중략)

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 1999.03a
• /
• pp.25-31
• /
• 1999

암석 내에 포함된 불연속면으로 인하여 암석은 압축하중 하에서 복잡한 거동을 한다. 이러한 복잡한 거동은 변형률강화(strain hardening), 변형률연화(strain softening), 부피팽창(dilatancy)등의 비선형 거동을 포함하는데, 이들은 균열의 성장, 상호작용(interaction), 연합(coalescence) 등을 통하여 발생한다(Brace et al., 1972; Kranz, 1983). 이와 같은 암석의 비선형적 거동을 설명하기 위하여 여러 형태의 균열모형이 개발된 바 있다(Costin, 1985; Nemat-Nasser ＆ Horii, 1982; Wang & Kemeny, 1993; Jeon, 1998). (중략)

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 1999.03a
• /
• pp.69-71
• /
• 1999

이 논문은 대구-포항 간 고속도로 건설공사 지역 중 제 7공구 지역에 대한 지반조사를 목적으로 실시한 지질조사의 결과다. 기존자료는 1대 5만 기계도폭(오인섭과 정국성, 1975)과 이 지역을 포함한 소위 가음단층대의 동부지역에 대한 지질구조를 조사를 연구한 이병주와 황재하(1997)의 논문 등이 있다. 야외에서의 지질조사는 개설될 고속도로를 중심으로 발달하는 노두에서 암상의 특징과 층리, 절리 및 단층 등과 같은 불연속면의 발달 특성을 관찰 기재하였다.(중략)

• Journal of the Korean Geotechnical Society
• /
• v.15 no.6
• /
• pp.219-238
• /
• 1999

In the present study, laboratory tests including the seepage-induced consolidation test, suction test, and desiccation shrinkage test are performed to investigate characteristics of the desiccation shrinkage in reclaimed hydraulic fills. Soil samples for laboratory tests are obtained from three sites (districts of Haenam, Kogeum and Koheung in Chunnam area). Desiccation shrinkage settlement caused by three dimensional volume change is numerically evaluated using finite difference technique based on the governing equation proposed by Abu-Hejleh & Znidarcic. Also characteristics of the desiccation shrinkage analyzed from the test results are used as input data for numerical evaluations. Further predicted total settlements including the self-weight consolidation settlement are compared with values measured at the site of Haenam district. Finally, effects of parameters related to the desiccation shrinkage on settlements are examined.

• The Journal of Engineering Geology
• /
• v.5 no.2
• /
• pp.167-179
• /
• 1995

The only three elements such as RQD, N -value and Es were used as a quantitative standard for the design of supporr pattern determidetion on subway line 8th in Seoul. Because the support pattern that was obtained by these elements could not he determined on the basis of the quantitative of geology and the orientations and properties of discontinuity planes, there have been some problems in determining the economic support pattern and tunnel stability. Therefore, in an attempt to determine the stable and economic support pattern with more quantitative elements, more flerrible rock mass classification with geologic conditions was performed by using RMR at 1745 sections and Q-system at 374 sections within Seongnam block on subway line 8th. Then, rusults by these two methods were compared with standard support pattern of the subway line 8th. Moreover, relationships between geology, geologic structures and topography to rock mass grades were studied. According to the rusult of this study, it is judged that the standard support pattern designed with PD-4 or PS - 4 should have been subdivided into 4~6 support patterns. Some sections where geologic structures such as faults and joints are developed tend to have rock mass grades. And they also have low rock mass grades near valley. On thr other hand, they show intermediate grades at piedmont area and the greatest ones at high mountains.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.11
• /
• pp.5-15
• /
• 2013

The end bearing capacity of rock-socketed drilled shafts under axial loading is investigated by Hoek-cell tests and a numerical analysis. From the test results, it was found that the ultimate end bearing capacity ($q_{max}$) was influenced by pile diameter, rock mass modulus and the spacing of discontinuity. A new ultimate end bearing capacity method is proposed by taking end bearing capacity influence factors, including rock mass discontinuity, based on field data. Through comparisons with other field data, the proposed $q_{max}$ method represents a definite improvement in the prediction of ultimate end bearing capacity of rock-socketed drilled shafts.

• The Journal of Engineering Geology
• /
• v.7 no.2
• /
• pp.91-99
• /
• 1997

In general, there are various approaches available in literature to model discontinuous rock masses and engineers are often confused which one to use for designing structures in rock masses. Modelling rock masses can be classified mainly into two approaches. One is discrete modelling of intact rock and discontinuities and the other is the equivalent continuum modelling. In this study five models are selected ;(1) Crack tensor model, (2) Equivalent volume defect model, (3) Damage model, (4) Micro - structure model (Parallel model and Series model), and (5) Homogenization model. Most of these models are mainly concerned with how to define additional strain due to discontinuities over the representative elementary volume (REV) and how to relate the stress field of discontinuities to that acting on the REV. The characteristics of these models are clarified by comparing with results of some laboratory tests.