• Explosives and Blasting
• /
• v.41 no.4
• /
• pp.17-28
• /
• 2023

Recently, the utilization of underground space for research facilities and resource development has been on the rise, expanding development from shallow to deep underground. The establishment of deep underground spaces necessitates a thorough examination of rock stability under conditions of elevated stress and temperature. In instances of greater depth, the stability is influenced not only by the geological structure and discontinuity of rock but also by the propagation of ground vibrations resulting from earthquakes and rock blasting during excavation, causing stress changes in the underground cavity and impacting rock stability. In terms of blasting engineering, empirical regression models and numerical analysis methods are used to predict ground vibration through statistical regression analysis based on measured data. In this study, single-hole blasting was conducted, and the pressure of the blast hole and observation hole and ground vibration were measured. Based on the experimental results, the blast pressure blasting vibration at a distance, and the response characteristics of the tunnel floor, side walls, and ceiling were analyzed.

• Tunnel and Underground Space
• /
• v.32 no.5
• /
• pp.285-297
• /
• 2022

We report results of Extended Leak-Off Test (XLOT) conducted in a large diameter borehole, which is drilled for installation of deep borehole geophysical monitoring system to monitor micro-earthquakes and fault behavior of major fault zones in the southeastern Korean Peninsula. The borehole was planned to secure a final diameter of 200 mm (or more) at a depth of ~1 km, with 12" diameter wellbore to intermediate depths, and 7-7/8" (~200 mm) to the bottom hole depth. We drilled first the 12" borehole to approximately 504 m deep and installed American Petroleum Institute standard 8-5/8" casing, then annulus between the casing and bedrock was fully cemented. XLOT was carried out for several purposes such as confirming casing and cementing integrity, measuring rock stress states. To that end, we drilled additional 4 m long open hole interval to directly inject water and pressurize into the rock mass using the upper API casings. During the XLOT, flow rates and interval pressures were recorded in real time. Based on the logs we tried to analyze hydraulic conductivity of the test interval.

• Tunnel and Underground Space
• /
• v.14 no.4
• /
• pp.295-303
• /
• 2004

For the deep underground excavation site with the geological complexity of soft seam and hard rock, the numerical analysis and in-situ measurement on the behaviors of roadway and surrounding rock according to stepwise excavation of the steep soft seam are carried out. The strata behavior is modeled using elasto-plastic FEM considering the empirical failure criteria of Hoek ＆ Brown and the strain-softening model. Hydraulic pressure capsule, MPBX and tape extensometer are installed around the roadway for the in-situ measurement of rock stress and deformation. Despite the complexity of geology and excavation procedure, the elasto-plastic analysis considering the empirical failure criteria of Hoek ＆ Brown and the strain-softening model shows good agreement with the in-situ measurement. Comparison of numerical modeling with in-situ measurement enables to predict the behaviors of the roadway and to obtain design parameters for the excavation and support at depth.

• Journal of the Korean GEO-environmental Society
• /
• v.22 no.12
• /
• pp.59-63
• /
• 2021

This study presented the characteristics and additive effects of the grout with mixing ratio for developing of high-efficiency grouting technology under high depth conditions. The laboratory investigation were conducted with Portland cement (OPC) and micro cement (S8000-E) including viscosity experiments, particle size analysis experiments, Gel-Time experiments and uniaxial compressive strength experiments. As a result of the viscosity experiment, it was shown that OPC is advantageous in terms of viscosity, but S8000-E is suitable when considering the passage of rock joint intervals through particle size analysis. The Gel-Time experiment shows that it is not that difficult with injection as a grout material even when silica fume (SF) was applied. The strength of the cured material is improved as increase in the content of silica fium (SF). Within the range of the study, the optimal mixing ratio obtained through various experiments is S8000-E, w/c=70%, silica fium (SF)=6%, and 7 days.

• Tunnel and Underground Space
• /
• v.34 no.1
• /
• pp.28-53
• /
• 2024

In general, high-level radioactive waste (HLW) generated as a result of nuclear power generation should be disposed within the country. Determination of the disposal site and host rock for HLW deep geological repository is an important issue not only scientifically but also politically, economically, and socially. Considered host rock types worldwide for geological disposal include crystalline rocks, sedimentary rocks, volcanic rocks, and salt dome. However, South Korea consists of various rock types except salt dome. This paper not only analyzed the geological and rock mechanical characteristics on a nationwide scale with the preliminary results on various rock type studies for the disposal host rock, but also reviewed the characteristics and possibility of various rock types as a host rock through deep drilling surveys. Based on the nationwide screening for host rock types resulted from literature review, rock distributions, and detailed case studies, Jurassic granites and Cretaceous sedimentary rocks (Jinju and Jindong formations) were derived as a possible candidate host rock types for the geological disposal. However, since the analyzed data for candidate rock types from this study is not enough, it is suggested that the disposal rock type should be carefully determined from additional and detailed analysis on disposal depth, regional characteristics, multidisciplinary investigations, etc.

• Tunnel and Underground Space
• /
• v.23 no.6
• /
• pp.480-492
• /
• 2013

After the introduction of geothermal power generation technology based on engineering reservoir creation that can be applied on non-volcanic region, industrial need for studies on the efficient and economic execution of costly deep-depth drilling work becomes manifest increasingly. However, since it is very difficult to predict duration and cost of boring work with acceptable reliability because of many uncertain events during the execution, efficient and organized work management for drilling is not easily achievable. Especially, the round trip that discretely occurs because of the abrasion of bit takes more time as the depth goes deeper and it has a great impact on the work performance. Therefore, a technology that can simulate the occurrence timing and depth of round trip in advance and therefore optimize them is essentially required. This study divided the abrasion state of bit into eight steps for simulation cases and developed a forecast algorithm, i.e., TOSA which can analyze the depth and timing of round trip occurrence. A methodology that can divide a unit section for simulation has been suggested; while the Bourgoyne and Young model has been used for the forecast of drilling rates and bit abrasion extent by section. Lastly, the designed algorithm has been systemized for the convenience of the user.

• Tunnel and Underground Space
• /
• v.24 no.2
• /
• pp.166-175
• /
• 2014

In this study, the thermal environment in a large scale coal mine located in Taebaek, Gangwondo was assessed by a field survey. In order to estimate the thermal environment, various heat stress indices such as WBGT, HSI, ESI, KATA index and effective temperature were investigated. Correlation analysis was also conducted. It was found that the thermal environment in most workplace was high. In particular, the correlation coefficient between HSI reflected in physiological fatigue characteristic and the maximum sweat evaporation heat was -0.834. This shows that the correlation coefficient have the most influence on HSI index. The factor which has the most influence on the maximum sweat evaporation heat is velocity of air. The thermal environment of high-depth coal mines is likely to be improved by installing a structure that enables the maximum prevention of extended digging, air doors, or the leakage of the inflow of air in the first shaft.

• Journal of the Korean Society for Railway
• /
• v.16 no.3
• /
• pp.202-206
• /
• 2013

A submerged floating railway is an innovative tunnel infrastructure passing through the deep sea independent of wave and wind so that high speed trains can run on it. It doesn't depend on water depth and is cost effective due to modular construction on land. The construction period can be reduced drastically. This paper introduces the concept design of a submerged floating railway, and for securing safety, proposes a method to analyze the structural behavior of the body in case of collision with a submarine. The theory of a beam with an elastic foundation was used to calculate the equivalent mass of the body so that the perfect elastic collision could be applied to calculate the collision velocity. The maximum deformation and bending moment was analyzed based on energy conservation. To verify the results, a collision analysis using a finite element analysis code was made. Comparing the results confirmed that this simplified collision analysis method gives enough accurate deformation and bending moment to be used for actual estimation in the initial design stage.

• Journal of Industrial Convergence
• /
• v.19 no.4
• /
• pp.37-48
• /
• 2021

The purpose of this study was to explore the meaning of the experience of Mucopolysaccharidosis patients receiving Enzyme Replacement Therapy(ERT). A qualitative research design was adopted. The participants were 7 patients diagnosed with MPS who is receiving ERT for several years. Data were collected through in-depth interviews from 1 July 2018 to 22 July 2018 for seven adult patients with MPS receiving ERT. Individual interviews were recorded, and transcribed data were analyzed using the inductive method of content analysis. The final 4 categories and 15 subcategories were identified. The 4 categories of the experience of Mucopolysaccharidosis patients receiving ERT were "Physical and psychological changes through ERT", "Continuous tunnel called ERT", "Accepting the reality" and "Cautious hope". This study provides deep insight into the experience of Mucopolysaccharidosis patients receiving ERT. Medical staff including nurses and related organizations should concern their distress during ERT as well as physical symptoms.

• Journal of the Korean Geotechnical Society
• /
• v.38 no.8
• /
• pp.67-74
• /
• 2022

The setting of the target area for ground stability evaluation during ground excavation is categorized into theoretical and empirical estimation methods and numerical analysis methods. Generally, the applied theoretical and empirical estimation methods include those by Peck (1969), Caspe (1966), and Clough et al. (1990). The numerical analysis method comprehensively considered the current status of the task section (maximum excavation depth section, ground condition vulnerable section, etc.). It reflected the results of performing two and three-dimensional numerical analyses on the weakest section. Therefore, this study shows an example of setting the scope of influence when excavating the vertical and tunnel sections of a 000-line double-track private investment project through the above theoretical, empirical, and numerical analysis methods.