• Journal of Korean Tunnelling and Underground Space Association
• /
• v.22 no.1
• /
• pp.1-21
• /
• 2020

The domestic abandoned mines are generating subsidence and it is difficult to predict this subsidence and evaluate the risk. The study of the subsidence risk evaluation using the existing numerical analysis only applies the integrative property to the geological structure and ground condition, and analyzes the goaf peripheral plastic domain. Also, there is a realistic limit that only restricted materials can be apprehended in securing the input information, which leads to the low reliability of the numerical analysis result. In this study, 2-dimensional modeling was performed by applying the field geological structure and ground information targeting abandoned mine where the subsidence occurred. Also, the analysis model was revised by repeating the numerical analysis for the difference between the real subsidence ground information and the analysis result to be minimized by modifying the ground property. This revision was automated by applying the optimization technique and the gradational optimal design method dividing multiple ground properties was developed.

• Journal of Korean Society of Transportation
• /
• v.21 no.4
• /
• pp.113-132
• /
• 2003

Using nonradial data envelopment analysis(DEA) under assumptions of strong disposability and variable returns scale, this paper annually estimates productive. technical and allocative efficiencies of three publicly-owned rail transit properties which are different in terms of organizational type: Seoul Subway Corporation(SSC, local public corporation), the Seoul Metropolitan Electrified Railways sector (SMESRS) of Korea National Railroad(the national railway operator controlled by the Ministry of Construction and Transportation(MOCT)), and Busan Urban Transit Authority (BUTA, the national authority controlled by MOCT). Using the estimation results of Tobit regression analysis. the paper next computes their true productive, true technical and true allocative efficiencies, which reflect only the impacts of internal factors such as production activity by removing the impacts of external factors such as an organizational type and a track utilization rate. And the paper also computes an organizational efficiency and annually gross efficiencies for each property. The paper then conceptualized that the property produces a single output(car-kilometers) using four inputs(labor, electricity, car & maintenance and track) and uses unbalanced panel data consisted of annual observations on SSC, SMESRS and BUTA. The results obtained from DEA show that, on an average, SSC is the most efficient property on the productive and allocative sides, while SMESRS is the most technically-efficient one. On the other hand. BUTA is the most efficient one on the truly-productive and allocative sides, while SMESRS on the truly-technical side. Another important result is that the differences in true efficiency estimates among the three properties are considerably smaller than those in efficiency estimates. Besides. the most cost-efficient organizational type appears to be a local public corporation represented by SSC, which is also the most grossly-efficient property. These results suggest that a measure to sort out the impacts of external factors on the efficiency of rail transit properties is required to assess fairly it, and that a measure to restructure (establish) an existing(a new) rail transit property into a local public corporation(or authority) is required to improve its cost efficiency.