• Journal of the Korean GEO-environmental Society
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• v.20 no.5
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• pp.13-21
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• 2019

There are many cuts or natural rock slopes that remain stable for a long time in the natural environment with steep slopes ($65^{\circ}$ to $85^{\circ}$). In terms of design practice, the rock mass consisting of similar rock condition and geological structures is defined as a good continuum rock slope, and during the process of decision making angle of this rock slope, it will be important to establish the geotechnical properties estimating method of the continuum rock on the process of stability analysis in the early stages of design and construction. In this study, the stability analysis of a good continuum rock slope that can be designed as a steep slope proposed a practical method of estimating the shear strength by induced from the Hoek-Brown failure criterion, and in addition, the design applicability was evaluated through the stability analysis of steep rock slope. The existing method of estimating the shear strength was inadequate for practical use in the design, as the equivalent M-C shear strength corresponding to the H-B envelope changes sensitively, even with small variations in confining stress. To compensate for this problem, it was proposed to estimate equivalent M-C shear strength by iso-angle division method. To verify the design applicability of the iso-angle division method, the results of the safety factor and the displacement according to the change in angle of the cut slope constructed at the existing working design site were reviewed. The safety factor is FS=16~59 on the 1:0.5 slope, FS=12~52 on the 1:0.3 slope, most of which show a 10~12 percent reduction. Displacement is 0.126 to 0.975 mm on the 1:0.5 slope, 0.152 to 1.158 mm on the 1:0.3 slope, and represents an increase of 10 to 15%. This is a slightly change in normal proportion and is in good condition in terms of stability. In terms practical the working design, it was confirmed that applying the shear strength estimated by Iso-angle division method derived from the H-B failure criterion as a universal shear strength for a good continuum rock mass slope was also able to produce stable and economic results. The procedure for stability analysis using LEM (Limit Equilibrium Analysis Method) and FEM (Finite Element Analysis Method) will also be practical in the rock slope where is not distributed fault. The study was conducted by selecting the slope of study area as a good rock condition, establishing a verification for which it can be applied universal to a various rock conditions will be a research subject later on.

• Journal of Korean Orthopaedic Sports Medicine
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• v.10 no.2
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• pp.47-53
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• 2011

Purpose: As the number of the anterior cruciate ligament (ACL) reconstruction has increased, the incidence of revision of ACL reconstruction due to reconstruction failure has been also increased. Therefore, authors analyzed the reason of the failure of ACL reconstruction and the clinical result of the ACL revision. Materials and methods: From February 1998 to July 2010, we selected 36 cases which was followed at least 12months after the ACL reconstruction failure. Duration from reconstruction to revision, the average duration was 60 months (5~334) and on first reconstruction, we used allograft on 23 cases (63.9%) and autograft on 13 cases (36.1%). For the main symptom of ACL reconstruction failure, instability was the most common symptom, and 35 cases (97.5%) were undergone only one reconstruction and 1case (2.5%) was undergone two reconstruction. Clinical results were evaluated by Lysholm knee joint score, pivot shift test, and Telos device. Results: Average follow-up duration of the patients was 21 months (12~40), and the reason for the ACL reconstruction failure, trauma was most common by 19 cases (52.8%), malposition of the femoral tunnel was 13 cases (36.1%), malposition of the tibia tunnel was 1case (2.8%), and failure of osteointegration was 3 cases (8.4%). On performing the ACL revision, we used allograft on 34 cases (94%) and autograft on 2 cases (6%), and 21 cases accompanied injury of the meniscus (medial meniscus 14 cases, lateral meniscus 7 cases). Lysholm knee joint score was improved from 66.5 points, preoperatively to 92 points on last follow-up (p<0.01). In most cases, patients were satisfied (92%) with the operation results. Tegner activity score was also improved from 2.0 points preoperatively to 6.2 points on the last follow-up. On Lachman and pivot sift test, 33 cases and 30 cases were improved to grade I respectively, and on stability test using Telos device, the bilateral difference was improved from mean 15.5 mm preoperatively to 4.5 mm on the last follow-up. Conclusion: After 1 year follow-up, Revision of ACL had a little anterior instability but it showed satisfactory result on clinical result and patient's subjective satisfaction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.545-560
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• 2019

During EPB TBM tunnelling, an appropriate application of additives such as foam and polymer is an essential factor to secure the stability of TBM as well as tunnelling performance. From the '90s, there have been many studies on the optimal injection of additives worldwidely contrary to the domestic situation. Therefore, in this paper, the foam, which is widely adopted for soil conditioning, was selected as an additive in order to investigate the effect of foam injection on TBM performance through a series of laboratory excavation tests. The excavation experiments were carried out on artificial sandy soil specimens with consideration of the variance of FIR (Foam Injection Ratio), FER (Foam Expansion Ratio) and $C_f$ (Surfactant Concentration), which indicate the amount and quality of the foam. During the tests, torque values were measured, and the workability of conditioned soil was evaluated by comparing the slump values of muck after each experiment. In addition, a weight loss of the replaceable aluminum cutter bits installed on the blade was measured to estimate the degree of abrasion. Finally, the foam injection ratio for the optimal TBM excavation for the typical soil specimen was determined by comparing the measured torque, slump value and abrasion. Note that the foam injection conditions satisfying the appropriate level of machine load, mechanical wear and workability are essential in the EPB TBM operational design.

• Economic and Environmental Geology
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• v.38 no.1
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• pp.91-99
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• 2005

Acid Rock Drainage(ARD) is the product formed by the atmospheric(i.e. by water, oxygen and carbon dioxide) oxidation of the relatively common iron-sulphur mineral pyrite($FeS_2$). ARD causes the acidification and heavy metal contamination of water and soil and the reduction of slope stability. In this paper the generation characteristics and the prediction of ARD of various cut slopes were studied. An attempt to classify the rocks into several groups according to their acid generation potentials was made. Acid Base Accounting(ABA) tests, commonly used as a screening tool in ARD predictions, were performed. Fourteen rock samples were classified into PAF(potentially acid forming) group and four rock samples into NAF(non-acid forming) group. The chemical analysis of water samples strongly suggested that ARD with high content of heavy metals and low pH could pollute the ground water and/or stream water.

• Tunnel and Underground Space
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• v.32 no.2
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• pp.107-119
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• 2022

Excavation-Disturbed Zone (EDZ) is an important design factor in constructing final disposal facilities for spent nuclear fuel, since EDZ affects mechanical stability including a spacing between disposal holes, and the hydraulic properties within EDZ plays a significant role in estimating in-flow rate of groundwater as well as a subsequent corrosion rate of a canister. Thus, it is highly required to characterize in-situ EDZ with precision and control the EDZ occurrence while excavating disposal facilities and constructing relevant underground research facilities. In this report, we not only reviewed EDZ-related researches carried out in the ONKALO facility of Finland but also examined appropriate methods for field inspection and quality control of EDZ occurrence. From the review, GPR can be the most efficient method for in-situ characterization of EDZ since it does not demand drilling a borehole that may disturb a surrounding environment of caverns. And the EDZ occurrence was dominant at a cavern floor and it ranged from 0 to 70 cm. These can provide useful information in developing necessary EDZ-related regulations for domestic disposal facilities.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.430-440
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• 2000

A series of studies such as geological logging data analysis, detailed geological survey, rock mass evaluation, in-situ and laboratory tests, rock strength and mechanical properties of the rock were concerned. The stability of the slope were carried out inorder to design the pit slope and individual benches using the stereographic projection analysis and numerical methods in Roto Pit of Pasir coal field. The bedding plane was one of the major discontinuities in the Roto Pit and the dip of which is about 60$^{\circ}$ in the northern part and 83$^{\circ}$ in the southern part. The dip of bedding becomes steeper from north to south. The plane and toppling failures are presented in many slopes. In laboratory test the average uniaxial compressive strength of mudstone was 9MPa and that of weak sandstone was 10MPa. In-situ test showed that the rocks of Roto north mining area are mostly weak enough to be classified in grade from R2(weak) to R3(medium strong weak) and the coal is classified in grades from R1(Very weak) to R2(Weak). The detailed stability analysis were carried out on 4 areas of Roto north (east, west, south and north), and 2 areas of Roto south(east and west). In this paper, the minimum factor of safety was set to 1.2 which is a general criterion for open pit mines. Using the stereographic projection analysis and the limit equilibrium method, slope angles were calculated as 30∼36$^{\circ}$ for a factor of safety greater than 1.2. Then these results were re-evaluated by numerical analysis using FLAC. The final slope angles were determined by rational described above. A final slope of 34 degrees can guarantee the stability for the eastern part of the Roto north area, 33 degrees for the western part, 35 degrees for the northern part and 35 degrees for the southern part. For the Roto south area, 36 degrees was suggested for both sides of the pit. Once the pit slope is designed based on the stability analysis and the safety measures, the stability of slope should be checked periodically during the mining operations. Because the slope face will be exposed long time to the rain fall, a study such aspreventive measures against weathering and erosion is highly recommended to be implemented.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.651-660
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• 2007

Acid drainage has been recognized as an environmental concern in abandoned mine sites for long time. Recently, the environmental and structural damage by acid drainage is a current issue in construction sites in Korea. Here, the author introduces the type of damages by acid drainage in construction sites and emphasizes the importance of geoscience discipline in solving the problem. Metasedimentary rock of Okcheon group, coal bed of Pyeongan group, Mesozoic volcanic rock. and Tertiary sedimentary and volcanic rocks are the major rock types with a high potential for acid drainage upon excavation in Korea. The acid drainage causes the acidification and heavy metal contamination of soil, surface water and groundwater, the reduction of slope stability, the corrosion of slope structure, the damage on plant growth, the damage on landscape and the deterioration of concrete and asphalt pavement. The countermeasure for acid drainage is the treatment of acid drainage and the prevention of acid drainage. The treatment of acid drainage can be classified into active and passive treatments depending on the degree of natural process in the treatment. Removal of oxidants, reduction of oxidant generation and encapsulation of sulfide are employed for the prevention of acid drainage generation.

• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.85-95
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• 2008

The purpose of this study is to reduce a high speed driving, it is a large scale traffic accident as the most dangerous fact on the highway. So traffic accidents related to high speed driving, a number of automated speed enforcement system has been established up to now. At present automated speed enforcement system in Korea control overspeed vehicle only in the specific spot. Because the drivers generally recognize the previous stated fact. therefore, we need speed control by new system. it is necessary to establish the automated traffic enforcement system based on the travel time speed. In conclusion, we obtain the desired results about automated traffic enforcement system based on the travel time speed. it is important that the number of traffic accidents has decreased and try to secure the safety of traffic.

• Tunnel and Underground Space
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• v.27 no.4
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• pp.243-252
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• 2017

Since the failure behavior of transversely isotropic rocks is significantly different from that of isotropic rocks, it is necessary to develop a transversely isotropic rock failure function in order to evaluate the stability of rock structures constructed in transversely isotropic rock masses. In this study, a spatial distribution function for strength parameters of transversely isotropic rocks is proposed, which is based on the Cassini oval curve proposed by 17th century astronomer Giovanni Domenico Cassini to model the orbit of the Sun around the Earth. The proposed distribution function consists of two model parameters which could be identified through triaxial compression tests on transversely isotropic rock samples. The original Mohr-Coulomb (M-C) failure function is extended to a three-dimensional transversely isotropic M-C failure function by employing the proposed strength parameter distribution function for the spatial distributions of the friction angle and cohesion. In order to verify the suitability of the transversely isotropic M-C failure function, both the conventional triaxial compression and true triaxial compression tests of transversely isotropic rock samples are simulated. The predicted results from the numerical experiments are consistent with the failure behavior of transversely isotropic rocks observed in the actual laboratory tests. In addition, the simulated result of true triaxial compression tests hints that the dependence of rock strength on intermediate principal stress may be closely related to the distribution of the microstructures included in the rock samples.

• Journal of the Mineralogical Society of Korea
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• v.20 no.3
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• pp.165-173
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• 2007

The KAERI Underground Research Tunnel (KURT) located in KAERI (Korea Atomic Energy Research Institute) was recently constructed following the site investigation in 2003. Its dimension is 180 m in length, 6 m in width, and 6 m in height, and it has a horseshoe-like cross-sec-lion and is located in the ground to the depth of 90 m. When the tunnel was dug into the ground with 100 m in length, fresh rocks, weathered rocks and fracture-filling materials were taken and examined by mineralogical and chemical analyses. There are phyllosilicate minerals such as illite, smectite and chlorite including calcite, which are filling some faults and cracks of the KURT rock. The illite and smectite usually coexist in the fracture, where their content ratio is different according to which mineral is predominant. There are high concentrations of U and Th in the rocks coated with iron-oxides and filled with secondary materials as compared with those in the fresh rocks. It seems that the radionuclides, which are slowly leached from the parent rocks or exist as a dissolved form in the groundwater and hydrothermal solution, may have been migrated along the fractures and thereafter selectively sorbed and coprecipitated on the iron-oxides and the fracture-filling materials. These results will be very useful far the evaluation of environmental factors affecting the nuclides migration and retardation when long-term safety is considered to the geological disposal of high-level radioactive wastes in the future.