회전익 무인항공기를 이용한 사면 안정성 평가 모니터링 기법에 관한 연구

Abstract

The entire country is the forestry with a ratio of 7:3 which are more than twice as wide as the land and road. However, due to industrialization and urbanization every year, the development area of forestry is constantly increasing. The growth in the development area of forestry has increased in not only the road but also the steep slope such as the retaining wall and cut slope of the downtown area. It is also an important factor causing damages such as landslides. Therefore, an efficient and systematic method are required to evaluate stability of steep slope. Recently, studies using unmanned aerial vehicles(UAVs) have been actively progressed in various fields at the inside and outside of the country. Because UAVs are inexpensive to operate and can quickly acquire data in a pervasive area, it is applied to disaster such as flood, fire, searching for marine or mountain, various monitoring, large-scale pesticide application, communication, image, geospatial information, design, geological survey and mapping, and natural disaster monitoring. For this study, the information of slope which is difficult to be measured is obtained through 3D image analysis using UAVs and through its information is carried out the stability evaluation for cut slope of open-pit limestone mine. The stability evaluation for cut slope was carried out at open-pit limestone mine with a width of about 70 m and a height of about 30 m. As a result of the stereographic projection analysis using 45 discontinuities data measured at the cut slope, there are two pole points in the envelope of plane failure, and 167 intersection lines in the envelope of wedge failure. Therefore, it can be estimated that the plane failure or wedge failure may be occurred. However, there is no possibility of toppling failure. As a result of the limit equilibrium method(LEM) based on the results of the stereographic projection analysis, the safety factor of plane type for Case 1 was estimated 0.992/0.875 at dry/wet condition, and 0.762/0.622 for Case 2 at dry/wet condition. It is less than the safety factor of 1.5/1/2 at dry/wet condition. The wedge failure was evaluated to be the safety factor of 7.857/7.337 for Case 1, 0.764/0.666 for Case 2. Therefore, Case 1 was evaluated to stable and Case 2 was evaluated to unstable condition, respectively. The safety factor for the final excavation of the analytical model calculated by the strength reduction method was evaluated to be stable at 3.21. The maximum shear strain() was confirmed to be concentrated at toe of the slope, and the total displacement was confirmed to be the largest value of 2.4 cm at toe. As a result of the analysis of 3D image in the four case using unmanned aerial vehicle, especially in the third case ground control point error was represented 1.7847 cm in the X axis, 1.5747 cm in the Y axis, 1.2530 cm in the Z axis, it is lowest error compared to other cases. It is generally correspond that the average error of 10 cm used for the ground control point in aerial photogrammetry is within the allowable error range. Therefore it is considered that the third image monitoring method is most suitable for risk analysis and calculation of blasted limestone volume in this study. As a result of the analysis of the 3D slope model and the risk analysis, it is possible to visually confirm the joint development status from the first to fourth aerial photogrammetry. Using Digital Elevation Model(DEM) and Orthomosaic, it was confirmed that quantitative limestone volume calculation analysis was possible by the difference of topographic changes before and after blasting.