• Journal of fish pathology
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• v.20 no.2
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• pp.179-187
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• 2007

Hydrolysis compound of cactus of opuntia genus, Opuntia ficus-indica var. saboten Makino, has predominant anti-bacterial, anti-fungal effects. In this study, we wont to know a preventive effects of bacterial disease on cultured flounder using the compound (MBT-01108), and physical and physiological responses of those fishes were examined additionally. The MBT-01108 shown any side effect on physical, hematological and histological conditions of fishes. Immunologically, CL (chemiluminescense) response were appeared at MBT-01108 (0.1%) feeding group for 4 weeks. The results of comparative livability at a experimental infection with E.tarda and S.iniae were 82.5% and 13.5% at 4 weeks MBT (0.1%) feeding group.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.869-886
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• 2018

Rockbolt is one of the most common supports used to reinforce discontinuous rock during underground excavation. Extra drain pipes are installed to improve excavation workability and the anchorage of rockbolts in water bearing ground. The drain pipe is effective in improving the workability by providing drainage path, but it is difficult to expect the reinforcement effect, increasing disturbance of the discontinuous rock mass and the construction cost. To solve this problem, dual purpose rockbolt (DPR) has been developed for the reinforcement of rock and the drainage of ground water. DPR was able to improve the mechanical and hydraulic stability of the rocks quickly and economically. Two kinds of DPRs using FRP (Fiber Reinforced Plastic) and steel were investigated for the mechanical and hydraulic performance. Also, the workability and stability of DPR were analyzed.

• Journal of fish pathology
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• v.23 no.3
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• pp.293-302
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• 2010

Effects of formalin on removal of Pseudodactylogyrus spp. were examined against naturally infected eel, Anguilla japonica (weight 89.9~96g) at a water temperature of $28^{\circ}$. Prior to experiments for removal of the parasite, the hematological toxicity of formalin bath at 0~500 ppm for 30 min~24 h was assessed by hematocrit values (Ht). Based on the results of Ht, appropriate methods of treatment, concentrations and durations, were examined in the main study. There was no significant (P>0.05) change of Ht in 100 to 200 ppm for 24 h. In contrast, Ht increased significantly (P<0.05) at above 300 ppm. This suggests that physiological damage was caused by formalin bath treating with 300 to 500 ppm. Formalin bath with 100 and 200 ppm for 24 h caused significant decreases (P<0.05) in the infection of the parasite. In conclusion, the 100 ppm formalin for 24 hour-bath was found most recommendable for the effective treatment of Pseudodactylogyrus spp. for the gills of the infected eel because of the median lethal concentration ($LC_{50}$) of formalin to eel; cumulative mortalities were found to be 0 and 13.3%, respectively, following 24 h bathing.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.442-456
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• 2018

Scaled model tests were performed to evaluate the reinforcement effect of rock bolts in anisotropic rock mass. For this purpose, two tunnel cases were experimented which had different tunnel sizes, rock strengths, anisotropic angles and coefficients of lateral pressure. The fully grouted rock bolts of the D25 deformed bar were modeled as the basting pins with bead and were systematically installed at the roof and the side wall of the model tunnel. As results of the first case experimentations, the unsupported model showed initial crack at the roof of tunnel, but the supported model with rock bolts showed initial crack at the floor of tunnel where rock bolts were not installed. The crack initiating pressure and the maximum pressure of the supported model with rock bolts were 11% and 7% larger than those of the unsupported model, respectively. Moreover, the effect of the existing discontinuities in anisotropic rock mass on the fracture behavior of tunnel was reduced in the supported model, and so the reinforcement effect of rock bolt turned out to be experimentally verified. As results of the second case experimentations considering different support patterns, the crack initiating pressures of models were larger and the reduction ratios of tunnel area according to applied load were smaller as the length and the quantity of rock bolts were larger. Therefore, it was found that the performance of the rock bolts turned out to be improved as they were larger.

• Journal of the Korean Geotechnical Society
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• v.33 no.3
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• pp.29-36
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• 2017

It has been known that rockbolt is one of important supports improving the support capacity with shotcrete in NATM tunnel. Also, it is necessary for the inclined system bolting to enhance the efficiency of installation in case of a narrow space such as cross passage and enlargement tunnel. However, there is no profound technical study for the effect of inclined rockbolt of systematic installation on the support mechanism and ground behaviour in NATM tunnel. In this study, the effects of the length and installation angle of rockbolt on the characteristics of support and ground reinforcement were analyzed by using 3D finite element numerical study. Through the numerical results for the parametric modelling of inclined rockbolt, the characteristics of mechanical behaviors between the axial force of rockbolt and the effect of ground reinforcement in regard to the various factors of the length and installation angle of rockbolt were verified and reviewed thoroughly. Also, it was shown that the installation angle of rockbolt for enhancing the arching effect in NATM tunnel was $45^{\circ}$, and the difference of the reinforcing effect for support between the installation angles of $75^{\circ}$ and $90^{\circ}$ was insignificant. The additional numerical studies for various condition would be carried out for practical design guideline of inclined rockbolt.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.231-238
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• 2012

The rockbolt functions as a main support, which restricts enlargement of the plasticity area and increases stability in the original ground around tunnels, and prevents a second deformation of an excavated surface by supplementing vulnerability arising from opening of the excavated surface. System bolting is generally applied if ground conditions are bad. System bolting is generally installed perpendicular to the excavation direction in every span. If a place is narrow, or it is difficult to insert bolts due to construction conditions, it may be connected and used with short bolts, or installed obliquely. In this study, laboratory model tests were performed to analyze the effect of the ground being reinforced by inclined bolts, based on a bending theory that assumes that the reinforced ground is a simple beam. In all test cases, deflections and vertical earth pressures induced by overburden soil pressure were measured. Total of 99 model tests were carried out, by changing the installation angle of bolts, lateral and longitudinal distance of bolts, and soil height. The model test results indicated that when the installation angle of bolts was less than $75^{\circ}$, deflections of model beams tended to increase rapidly. Also, the relaxed load that was calculated by earth pressure was rapidly increased when the installation angle of bolts was less than $75^{\circ}$. However, the optimum installation angle of inclined bolts was judged to be in the range of $90^{\circ}{\sim}75^{\circ}$. Also, as might be expected, the reinforcement effect of bolts was increased when the longitudinal and lateral distance of bolts was decreased.

• Tunnel and Underground Space
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• v.24 no.5
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• pp.395-403
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• 2014

In this study, a steel pipe type rockbolt manufactured from special material was developed which has high strength and lightweight characteristics. Achievement of grout filling between rockbolt and hole wall was investigated through grout injection tests. Yield force of the developed rockbolt was also examined through tensile tests, which was compared with that of the deformed bar type rockbolt. In addition, the strength and elongation properties of the developed rockbolt were investigated through pull-out tests at three domestic sites showing different RMR classes. It is finally supposed that the developed rockbolt can be suitable for the permanent tunnel support because it has high strength and high durability rather than deformed bar type rockbolt.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.3
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• pp.187-195
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• 2005

When a tunnel is excavated below groundwater table, the groundwater flow occurs towards the tunnel resulting in the seepage pressure. In this paper, the effect of groundwater flows on the behavior of shotcrete lining installed between ground-liner interfaces was studied considering permeability ratio between the ground and the shotcrete into account. Three-dimensional coupled finite element analysis was performed for this assessment. Seepage forces will seriously affect the shotcrete behavior since arching phenomena do not occur in seepage forces. A parametric study was conducted on the various tunnelling situations including interfacial properties between ground and shotcrete lining, the shape of tunnel cross-section and the thickness of liner, etc. Moreover, the convergence-confinement method (CCM) of a NATM tunnel considering seepage forces was proposed. The result showed that the more water tight is the shotcrete, the smaller is the convergence and the larger is the internal pressure. Therefore, the watertight fiber-reinforced shotcrete is found to be even more advantageous when used in under water tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.141-149
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• 2006

For application of NATM, the self-supporting until installation of the supporting system must be satisfied. However, the face of a tunnel are always unsupported and therefore it is fairly vulnerable to tunnel collapses. Face blots are well known and widely used to prevent the deformation of the tunnel face and its circumference, which are installed horizontally toward the tunnel axis generally. To maximize the supporting effect of face bolts, this study has analysed the effective design patterns of face bolts by changing their installation angles. As the conclusion, it has been found that the axial displacement of the face increases slightly by installing the outermost bolts upward from the axis but surface settlement at 2.5D behind the face decreases up to 18%.

• Geotechnical Engineering
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• v.14 no.4
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• pp.17-32
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• 1998

has been much progress in theories and construction techniques to secure the stability of the underground structures. Recently, several studios have shown that it is possible to predict the existence of discontinuities ahead of a tunnel face by analyzing 3-dimensional absolute displacements measured during tunnel excavation. This paper concentrated on the development of a methodology to predict the existence and location of the discontinuities, or the void space(abandoned mine) , by performing 3-dimensional FEM analysis and considering the stress relocation caused by arching effect during excavation. Also, this study tried to verify deformation for choosing the most suitable support system. The results of this study might provide a way of safer and economical tunnel construction by utilizing the in-situ monitoring data.