• 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.19 no.2
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• pp.145-152
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• 2009

Joints are planar tensile opening-mode fractures whose relative motion, as the fracture propagates, is perpendicular to bedding plane and occur in a systematic manner to form a joint set. This paper discusses the mechanical control of joint propagation, the relationship between join spacing and layer thickness, the join saturation, the frequency distribution of join spacing, the joint density, the cross joint, and the development mechanism of joint from a lot of recent joint studies in sedimentary rocks.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.643-648
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• 2014

Understanding of fracture networks and rock mass properties during tunnel construction is extremely important for the prediction of dangers during excavation, and for deciding on appropriate excavation techniques and support. However, rapid construction process do not allow sufficient time for surveys and interpretations for spatial distributions of fractures and rock mass properties. This study introduces a new statistical approach for predicting joint distributions at foreside of current excavation face during the excavation process. The proposed methodology is based on a cumulative space diagram for joint sets. The diagram displays the cumulative spacing between adjacent joints on the vertical axis and the sequential position of each joint plotted at equally spaced intervals on the horizontal axis. According to the diagram, the degree of linearity of points representing the regularity of joint spacing; a linear trend of the points indicates that the joints are evenly spaced, with the slope of the line being directly related to the spacing. The linear points which are stepped indicates that the fracture set show clustered distribution. A clustered pattern within the linear group of points indicates a clustered joint distribution. Fractures surveyed from an excavated space can be plotted on this diagram, and the diagram can then be extended further according to the plotted diagram pattern. The extension of the diagram allows predictions about joint spacing in areas that have not yet been excavated. To test the model, we collected and analyzed data during excavation of a 10-m-long tunnel. Fractures in a 3-m zone behind the excavation face were predicted during the excavation, and the predictions were compared with observations. The methodology yielded reasonably good predictions of joint locations.

• Explosives and Blasting
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• v.23 no.2
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• pp.37-44
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• 2005

Recent studies reported that natural block size of rock and joint orientation highly affect on rock fragmentation. In this study, blasting test using high strength cement mortar was carried out to verify this fact. The result of this test indicated that fragmentation is influenced by the joint interval, and at same joint interval condition, fragmentation depends on joint orientation. These results are significantly coincident with field investigations.

• Explosives and Blasting
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• v.35 no.4
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• pp.1-9
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• 2017

This study undertakes an evaluation of blast effect through the analysis of the contribution rate and effect that different artificial joint number, artificial joint spacing and artificial joint angle have on blast velocity. Blast velocity according to the different state of the artificial joint was obtained using AUTODYN, a dynamic analysis program. The result of the numerical analysis was subjected to further normalization analysis. For the contribution rate of design factors was analyzed using the robust design method. The orthogonal array used in the analysis was $L_9(3^4)$ and each parameters were having 3 levels. The result of normalization analysis regarding the artificial joint angle was indicated a tendency in which blast velocity decreased. The result of analyzing blast velocity regarding artificial joint spacing and artificial joint angle was indicated a tendency in which blast velocity decreased as artificial joint spacing increased when the angle was perpendicular. In the case of blast velocity contribution rates they were ranked in the descending order of artificial joint angle, artificial joint number, artificial joint spacing.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.351-363
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• 2009

Two orthogonal joint sets develop well only in sandstone beds in the sandstone-mudstone sequences of Gumi and Dasa outcrops within Cretaceous Gyeongsang Basin. And various joint data are similar in the beds of the same thickness in both outcrops, meaning that the joint sets were homogeneously produced by extensional deformation in the same regional stress field. Most of joints in the sandstone beds are orthogonal to, and confined by bed boundaries, which are believed to be formed by hydrofracturing during consolidation after burial. Two orthogonal joint sets are considered to be almost coeval on the basis of mutual abutting relationship which makes up fracture grid-lock and a product of rapid switching of ${\sigma}_2$ and ${\sigma}_3$ axes with constant ${\sigma}_1$ direction oriented to vertical. The joint sets in the sandstone beds show planar surfaces, parallel orientations and regular spacing, with joint spacing linearly proportional to bed thickness. The spacing distributions of the joints seem to correspond to log-normal to almost normal distribution in most of the beds. But multilayer joints do not display regular spacing and dominant size. Either joint set in this study is characterized by a high level of joint density and a saturated spacing distribution as indicated by the mode/mean ratio values and the Cv(coefficient of variance) values. Joint aperture tends to increase with the vertical length of the joints controlled by bed thickness.

• Tunnel and Underground Space
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• v.13 no.5
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• pp.344-352
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• 2003

The procedures to correct sampling biases for discontinuity data obtained from 1D survey line(borehole or scanline) is addressed. The Probability of intersection between the survey line and a circular discontinuity is considered, and a correction far orientation bias is developed assuming discontinuities as equivalent circular disks. The correction incorporates the effect of the angle between the direction of survey line and each discontinuity plane belonging to the discontinuity cluster, size of each discontinuity and length of the survey line. A procedure is provided to estimate unbiased discontinuity spacing parameters using the discontinuity spacing data based on the measurements carried out on a finite length of the survey line.

• Tunnel and Underground Space
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• v.19 no.1
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• pp.1-10
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• 2009

Site characterization for structural stability in rock masses mainly involves the collection of joint property data, and in the current practice, much of this data is collected by hand directly at exposed slopes and outcrops. There are many issues with the collection of this data in the field, including issues of safety, slope access, field time, lack of data quantity, reusability of data and human bias. It is shown that information on joint orientation, spacing and roughness in rock masses, can be automatically extracted from LIDAR (light detection and ranging) point floods using the currently available Split-FX point cloud processing software, thereby reducing processing time, safety and human bias issues.

• Proceedings of the KSEG Conference
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• 2003.04a
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• pp.27-35
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• 2003

시추공에서 측정된 절리자료의 샘플링 편향오류를 보정하는 절차를 기술하였다. 시추공에서 절리의 방향이 관측될 수 있는 확률은 시추공에 대한 절리의 상대적인 방향 이외에도 절리의 크기, 절리의 모양 및 시추공의 반경 과 길이와 같은 요인에 의하여 결정될 수 있으며, 이러한 요인들에 의하여 나타날 수 있는 절리자료의 방향편향을 보정할 수 있는 방법론을 제시하였다 유한 길이의 시추공으로부터 산정된 절리의 간격분포는 샘플링 영역인 시추공 길이의 영향에 의한 산정치의 오류를 내포하고 있으며, 이에 대한 보정법을 고찰하였다.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.337-349
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• 2006

Seven hundred and fifty one fractures of the rhyolitic tuffaceous rock masses were mapped using 6 scanlines placed on rock slope exposures that were within 8.02 km of Busan-Ulsan highway. These data were analyzed to find the number of fracture sets that exist in the rock slopes and the probability distributions of orientation, spacing, trace length and fracture size in 3-D for each of the fracture sets. All the fracture set orientation distributions exhibit high variability. The Fisher distributions were found to be unsuitable to represent the statistical distribution of orientation for most of the fracture sets. The probability distributions, gamma, exponential and lognormal were found to be highly suitable to represent the distribution of spacing and semi-trace length of fracture sets. In obtain-ing these distributions, corrections were applied for sampling biases associated with spacing and trace length. The generated fracture system in 3-D was used to make predictions of fracture traces for each fracture set on 2-D win-dows. Developed stochastic 3-D fracture network for the rock mass was validated by comparing statistical proper-ties of the observed fracture traces on scanlines with the predicted fracture traces on the scanlines. This exercise fumed out to be successful.