Tunnel and Underground SpaceISSN:1225-1275(Print) 2287-1748(Online)한국암반공학회

With the increasing share of carbon-free energy generation, energy storage system (ESS) technologies are gaining attention as a means to stably and efficiently utilize electrical energy. In Korea, battery energy storage systems (BESS) have been actively adopted and researched for grid stabilization due to their high efficiency and rapid response. However, concerns remain regarding fire hazards, supply chain risks, and waste battery management. To address these limitations, various safe and sustainable ESS technologies have been proposed. This study conducts a comprehensive performance assessment of multiple ESS technologies by comparing their advantages and disadvantages, lifetime, round-trip efficiency, storage capacity, and levelized cost of storage (LCOS). As a result, gravity energy storage (GES) emerges as a promising alternative. Among these, solid gravity energy storage (SGES) is highlighted for its flexible, scalable, efficiency, sustainable, safety, durable, and economical benefits. Additionally, to evaluate the applicability of SGES using domestic mines, the influence of different cable diameters and hoist power outputs on storage capacity was analyzed. The results reveal that cable diameter is the most influential parameter, with a 76.2 mm diameter delivering the maximum storage capacity. The places with storage capacities of 3 MWh or more were Jangseong Mines (2 shafts), and the shafts with storage capacities of 2 MWh or more were Samcheok Coal Mine (1 shaft), Hamtae Coal Mine (1 shaft), Yeonhwa Mine (1 shaft), Dongwon Coal Mine (1 shaft), and Handuk Iron Mine (1 shaft), a total of 5 locations. The places with storage capacities of 1 MWh or more were evaluated to be 16 shafts, and when the storage capacities of all shafts in the country were evaluated, it was analyzed that 60.52 MWh of electricity could be stored. The findings of this study aim to assess the future applicability of domestic mines for ESS implementation and to provide foundational data for rock mass stability evaluations and demonstration studies.

In tunnel blasting operations, the factors that determine blasting efficiency can be broadly classified into two main categories: the physical and mechanical properties of the bedrock and the mechanism of blasting techniques. In South Korea, most tunnel blasting pattern design standards have been established for granite or gneiss, while design guidelines for limestone sections remain limited. This study aims to determine the optimal specific charge and appropriate cut blasting methods for limestone by combining theoretical analysis and full-scale field test blasting. The results show that the specific charge required for limestone is approximately 40% lower than that for typical granite or gneiss. It was also found that a specific charge of approximately 0.670 kg/m³ is sufficient to achieve an advance length of 3.0 meters. Considering the geological structure and formation characteristics of sedimentary rocks, the proposed SAV-Cut blasting method, which combines inclined and parallel cut blasting techniques, demonstrated significantly improvement in constructability and overall efficiency.

Buffer materials in a high-level radioactive waste disposal system serve as a key component of the engineered barriers by delaying radionuclide migration and protecting the disposal canister. Over extended periods, these buffer materials undergo a transition from an unsaturated to a saturated state under high-temperature conditions induced by radioactive decay heat and groundwater inflow from surrounding rock. The buffer materials exhibit swelling properties upon saturation, making it critical to predict the long-term capacity of swelling performance throughout the disposal period, which spans hundreds of thousands of years. In this study, the Barcelona Basic Model, a representative model for the elastoplastic behavior of unsaturated soils, was modularized within the thermo-hydro-mechanical coupled numerical simulator, OGS-FLAC3D. Following the construction of the numerical code, we conducted validation through comparative analysis with case studies evaluating volumetric changes along the pathways of mean effective stress and suction variations. The numerical simulation results and validation case studies showed a good agreement. Based on the developed module, we expect to use the OGS-FLAC3D simulator in various research studies related to the behavior of buffer materials in disposal systems.

This study developed an application that automatically aggregates the number of loading and dumping events by using the work sound generated during mine haulage operations. To this end, the work sound was collected by riding directly on the loading and dumping work truck at Daesung MDI Danyang Office located in Danyang-gun, Chungcheongbuk-do. The singularity of the work sound of loading and dumping operations was analyzed. In order to aggregate the number of loading and dumping operations, each singularity was quantified and the classification criteria were divided. The developed work sound classification application starts to recognize the surrounding noise when the tablet PC receives the Bluetooth beacon signal, and the number of times is automatically counted when the loading and dumping operation sound is recognized according to the previously classified criteria. As a result of the field experiment, the count of the number of times was 100% successful, and the unit time required for truck work could be accurately measured.

This study focuses on modifying the existing erector system for continuous shield TBM (Tunnel Boring Machine) excavation to enable the installation of helical segments. First, the degrees of freedom (DOF) of conventional erectors currently in use were analyzed, and the feasibility of assembling helical segments was evaluated. Additional DOF required for helical segment assembly were identified, and a modification method for the erector was proposed. Based on this analysis, a three-dimensional design model of the modified erector was developed. Furthermore, a detailed assembly scenario for helical segments was established, and a dedicated program was created to detect contact and collision between equipment and segments during the assembly process. Using this virtual simulation, the performance of the modified erector in assembling helical segments was verified.

본 연구에서는 균열암반에 위치한 지하연구시설 내 터널 근계영역인 굴착교란영역의 투수특성과 분포양상을 평가하였다. 자체 개발된 고정밀 수리시험장비를 암반터널 내 수평시추공에 적용하여 정압주입시험을 수행함으로써, 현지 압력 및 유량 자료를 획득하였고, 정상류/비정상류 해석을 통해 심도(터널 벽면으로부터의 거리)에 따라 수리전도도를 도출하였다. 연구 분석 결과, BBH-1 시추공의 경우 터널 벽면으로부터 멀어지면서 수리전도도가 10배(1 order) 정도 감소하였으며, 기존 선행 연구들의 굴착교란영역 내 투수도 변화양상과 유사한 결과를 나타냈다. 그러나 BBH-2 시추공에서는 벽면에서부터 떨어진 일부 심도에서 전체 투수특성 변화경향에서 벗어나는 국부적으로 높은 투수도가 나타났다. 이를 통해, 굴착공동 주변 암반의 투수특성이 반드시 일정한 감소변화나 분포양상을 따르지 않는 경우도 있다는 것을 알 수 있고, 따라서 현장수리시험 수행을 통해 근계영역의 수리특성을 직접적으로 파악하는 것이 중요하다고 할 수 있다. 본 연구의 장비와 수행방법 및 분석과정, 그리고 도출된 투수도 결과들은 향후 굴착공동 주변 수리적 EDZ의 정밀 수리특성 평가를 위한 통합시스템 개발의 기초가 될 것으로 사료된다.

As surface space becomes increasingly limited, underground space development is being accelerated to address the demand for efficient land utilization. Excavation and construction for underground space often induce multiple microfractures in the rock mass, requiring rock grouting to ensure structural reinforcement and groundwater sealing. Cement grout is commonly used as the injection material for rock grouting; however, it is prone to bleeding over time due to its properties. Excessive bleeding can compromise grout integrity and the stability of surrounding rock formations, necessitating its consideration in grout mix design and implementation. In deep underground, geothermal heat and groundwater result in high-temperature conditions. Therefore, understanding grout bleeding characteristics under high-temperature conditions is critical for selecting suitable grout materials and optimizing mix designs for in-situ application. This study aims to analyze the bleeding characteristics of cement grout for rock grouting under high-temperature conditions. In this study, Portland cement and micro-cement were used as grout materials, and bleeding characteristics were analyzed with respect to cement type, water–cement ratio, elapsed time, and temperature.