• Proceedings of the Korean Geotechical Society Conference
• /
• 1998.05a
• /
• pp.3-34
• /
• 1998

The stability condition of rock slopes is greatly affected by the geometry and strength parameters of discontinuities in the rock masses. Rock slopes Involving movement of rock blocks on discontinuities are failed by one or combination of the three basic failure modes-plane, wedge, and toppling. In rock mechanics, practically all the parameters such as the joint set characteristics, the rock strength properties, and the loading conditions are always subject to a degree of uncertainty. Therefore, a reasonable assessment of the rock slope stability has to include the excavation of the multi-failure modes, the consideration of uncertainties of discontinuity characteristics, and the decision on stabilization measures with favorable cost conditions. This study was performed to provide a new numerical model of the deterministic analysis, reliability analysis, and reliability-based optimization for rock slope stability. The sensitivity analysis was carried out to verify proposed method and developed program; the parameters needed for sensitivity analysis are design variables, the variability of discontinuity properties (orientation and strength of discontinuities), the loading conditions, and rock slope geometry properties. The design variables to be optimized by the reliability-based optimization include the cutting angle, the support pressure, and the slope direction. The variability in orientations and friction angle of discontinuities, which can not be considered in the deterministic analysis, has a greatly influenced on the rock slope stability. The stability of rock slopes considering three basic failure modes is more influenced by the selection of slope direction than any other design variables. When either plane or wedge failure is dominant, the support system is more useful than the excavation as a stabilization method. However, the excavation method is more suitable when toppling failure is dominant. The case study shows that the developed reliability-based optimization model can reasonably assess the stability of rock slopes and reduce the construction cost.

• Journal of Welding and Joining
• /
• v.33 no.2
• /
• pp.8-13
• /
• 2015

This study was carried out to evaluate mechanical properties of the jointed Al6061/HT590 alloys by friction stir welding (FSW). FSW was conducted under the conditions with tool rotating speed of 500 RPM and traveling speed of 300 mm/min., where Ar gas was introduced to prevent the materials from corrosion during the welding process. Electron back-scattering diffraction (EBSD) was used to characterize microstructures such as grain size, misorientation angle and crystal orientation. Evolution of intermetallic compounds in Al6061 during the process were examined in terms of morphology, size and aspect ratio at three distinct zones Al base material, heat affected zone and stir zone, where transmission electron microscope (TEM) was used. It was revealed that FSW gave rise to refinement of grains as well as growth of intermetallic compounds in Al6061. The morphological changes of intermetallic compounds exerted an influence on mechanical properties, resulting in occurrence of fracture in the part of the base material instead of the jointed parts (heat affected zone and stir zone). This study systematically evaluated the microstructural evolutions during the FSW for joining Al6061 with HT590 and their effect on mechanical properties.

• Tunnel and Underground Space
• /
• v.24 no.4
• /
• pp.282-288
• /
• 2014

Stoping method has been acknowledged as one of the typical metalliferous underground mining methods. Notwithstanding with the popularity of the method, the majority of stoping mines are suffering from excessive unplanned dilution which often becomes as the main cause of mine closure. Thus a reliable unplanned dilution management system is imperatively needed. In this study, reliable unplanned dilution prediction system is introduced by adopting artificial neural network (ANN) based on data investigated from one underground stoping mine in Western Australia. In addition, contributions of input parameters were analysed by connection weight algorithm (CWA). To validate the reliability of the proposed ANN, correlation coefficient (R) was calculated in the training and test stage which shown relatively high correlation of 0.9641 in training and 0.7933 in test stage. As results of CWA application, BHL (Length of blast hole) and SFJ (Safety factor of Joint orientation) show comparatively high contribution of 18.78% and 19.77% which imply that these are somewhat critical influential parameter of unplanned dilution.

• The Journal of Engineering Geology
• /
• v.18 no.2
• /
• pp.159-166
• /
• 2008

We have a question about the changing possibility of orientation of discontinuities through the depth of under-ground. To know this, the data from Honam coalfield composed of shale, sandstone and coal and Suwon area which crops out mica schist, were analyzed the discontinuities measured by BIPS and Televiewer. In Honam coalfield the orientations of joints are changed at 30-40 m depth of underground and in Suwon area they are changed around 20 m depth. To compared the results from Honanam coalfield and Suwon area, there are different rock type and geologic structure. However, the attitude of the discontinuities are changing at 20-30 m depth of underground.

• The Journal of Engineering Geology
• /
• v.27 no.3
• /
• pp.207-215
• /
• 2017

The northern extension of the Dongrae Fault is inferred to transect the Ulsan Fault in the Gueo-ri area, Oedong-eup, ~15 km SE of Gyeongju City, Gyeongbuk province, S Korea. We conducted geological and geophysical (magnetic, electrical resistivity, and frequency domain electromagnetic) surveys to identify the extent and orientation of the Dongrae Fault in this region. Through joint interpretation of the geological and geophysical data sets, we confirm the presence of the Dongrae Fault and determine its strike ($N14^{\circ}E$). The Dongrae Fault is thought to cross the Ulsan Fault near Ipsil Bridge in the Gwangeo-ri area. Geophysical surveying revealed a fault damage zone that widens to the south, with a typical width of >200 m. Geological field surveys did not delineate the geometry of the Dongrae Fault because alluvial deposits overlie the fault in this area.

• Tunnel and Underground Space
• /
• v.16 no.6 s.65
• /
• pp.451-466
• /
• 2006

Analysis of slope behavior concerning the structural characteristics of field rock mass can be processed by virtue of borehole information of joint orientation and position acquired from DOM drilled core. Anticipated sliding potential of pre-failed rock slope is analyzed and the regional slope instability is investigated by inspecting the hazardous joints and blocks the traces of which is projected on the cut-face. Cross section has been set at the center of rock slope and the traces of both joints and tetrahedral blocks, which potentially can induce the slope failure, are drawn to investigate the failure modes and the triggering mechanism. Automated monitoring system has been established to measure the slope movement and especially, inclinometer has been installed inside DOM borehole to analyze the slope movement by considering the internal rock structure. Algorithms for predicting the slope failure time have been reviewed and the significance of heavy rainfall on the slope behavior has been investigated.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.8
• /
• pp.15-27
• /
• 2004

Sliding aspects of rock slope, where large-scaled tension cracks are induced during preliminary excavation, have been analyzed. Structure of rock mass is investigated by performing the electrical resistivity survey and the orientations and positions of discontinuities are measured from DOM-drilled core log. Geological evidence far primary failure movement has been detected and clay minerals which possess swelling properties are identified through XRD analysis. Slope stability is examined by considering the orientations of discontinuities and their trace distributions on the cut-face and neighboring natural slope surface. Both orientations and positions of failure-invoking discontinuity planes, traces of which are exposed within the anticipated sliding region, are concerned fur analyzing the preferred sliding directions. Regional sliding vectors are assessed based on the relative positions of potential sliding planes in the boreholes and the general trend of anticipated failure movement of rock slope is also investigated.

• Journal of rehabilitation welfare engineering & assistive technology
• /
• v.7 no.2
• /
• pp.47-54
• /
• 2013

In this paper, we present an inertial sensor-based motion capturing system to measure and analyze whole body movements. This system implements a wireless AHRS(attitude heading reference system) we developed using a combination of rate gyroscope, accelerometer and magnetometer sensor signals. Several AHRS modules mounted on segments of the patient's body provide the quaternions representing the patient segments's orientation in space. We performed 3D motion capture using the quaternion data calculated. And a method is also proposed for calculating three-dimensional inter-segment joint angle which is an important bio-mechanical measure for a variety of applications related to rehabilitation. To evaluate the performance of our AHRS module, the Vicon motion capture system, which offers millimeter resolution of 3D spatial displacements and orientations, is used as a reference. The evaluation resulted in a RMSE of 2.56 degree. The results suggest that our system will provide an in-depth insight into the effectiveness, appropriate level of care, and feedback of the rehabilitation process by performing real-time limbs or gait analysis during the post-stroke recovery process.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.158-158
• /
• 2022

Ecological drought consequences have received a lot of attention in recent years. Thus, ecological drought was proposed as a new drought category to characterize the impact of drought on ecosystems. The current study used a unique drought index, the standardized supply-demand water index (SSDI), and a run theory to detect ecological drought occurrences and characteristics such as drought-affected area, drought severity, drought duration, drought frequency, and drought orientation in the Hwang River, an environmentally valuable region. Hence, to assess drought-prone areas, the bivariate probability and return period will be calculated using a two-dimensional joint copula. The core results show that (a) the Spatio-temporal characteristics of ecological drought were successfully recognized using the spatial and temporal identification approach; (b) in comparison to the SPEI meteorological drought index, the SSDI is more credible and can more readily and effectively capture the entire properties of ecological drought information; (c) the Hwang river had seen the most severe drought occurrences between the late 1990s and the mid-2020s, with 48.3 percent occurring before the twenty-first century; (d) Severe ecological drought occurrences occurred more frequently in most areas of the Hwang River (e) Only the drought duration and severity in the Hwang area were more responsive to temperature when temperatures rise around 1.1℃, the average drought duration and severity rise around 16 % and 26 %, respectively. This suggested that the Hwang River has been exposed to more severe heat stress in the twenty-first century. Thereupon droughts in the twenty-first century occurred with bigger affected regions, longer durations, higher frequency, and more intensity.

• Journal of the Microelectronics and Packaging Society
• /
• v.17 no.4
• /
• pp.11-17
• /
• 2010

The electromigration phenomenon in lead-free flip-chip solder joint has been one of the serious problems. To understand the mechanism of this phenomenon, the crystallographic orientation of Sn grain in the Sn-Ag-Cu solder bump has been analyzed. Different time to failure and different microstructural changes were observed in the all test vehicle and bumps, respectively. Fast failure and serious dissolution of Cu electrode was observed when the c-axis of Sn grain parallel to electron flow. On the contrary of this, slight microstructural changes were observed when the c-axis of Sn perpendicular to electron flow. In addition, underfill could enhance the electromigration reliability to prevent the deformation of solder bump during EM test.