• Tunnel and Underground Space
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• v.33 no.3
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• pp.126-140
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• 2023

In this study, the cause of subsidence in limestone mine was analyzed using a LiDAR-based geometry model. Using UAV and ground-based LiDAR systems, a precise geometry model was constructed for the subsidence surface and mine tunnel, and the results of on-site geological survey and rock mass classification were utilized. Through the geometry model, distribution of thickness of crown pillar and faults around the subsidence area, calculation of the volume of the subsidence area and subsidence deposit, and analysis of the subsidence surface inclination were conducted. Through these analyzes, the causes of ground subsidence were identified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.3
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• pp.449-456
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• 2018

In this study, a soil nail design method for a stability analysis of local instability with nail reinforced slope was proposed. The failure mechanism of a local instability of slope was studied and a theoretical equation to estimate the stability of slope was developed. Using the developed equation, the stability analysis was performed according to installation conditions of soil nail such as a slope inclination, a thickness of soil layer, a nail inclination, and a nail spacing. Considering those design factors, a sensitivity analysis for each influence factors was conducted. Analysis results showed that the safety factor of reinforced slope with nail was higher than the slope without nail. In addition, the safety factor of slope according to ground condition was increased in the order of dry, saturated, and seepage condition.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.273-279
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• 2014

The mass mortalities have been occurring of Korean scallop Patinopecten yessoensis from 1997's to now in Korea east sea. Cages behavior and interference effect (common name; curtain effect) between scallop cages were investigated in culture grounds on the eastern coastal waters of Korea for understand to mechanism of rising about mass mortalities of Korean scallop quickly. The first experiment was carried out in circulating water channel to assess inclination angel from relationship between velocity and cages interval, velocity with culture cages position. An angle of inclination of scallop culture cages were 94.6 to 92.3 degree under a several velocity which were from 0.1 m/s and 131.9 to 118.1 degree under 0.5 m/s with cages interval were 1 m, 94.3 to 91.0 degree under velocity is 0.1 m/s and 133.2 to 122.4 degree under 0.5 m/s with cages interval were 1.5 m and 94.6 to 96.4 degree under velocity is 0.1 m/s and 131.7 to 131.8 under 0.5 m/s with cages interval were 2 m. The second experiment was designed to prove the tank test. Velocities were measured inside and outside of the scallop culture ground at eastern sea of Korea. The velocity of inside of the culture was the slowest as 0.1m/s. In this result, interference between former cage and after cage was occurred.

• Journal of the Korean GEO-environmental Society
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• v.9 no.5
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• pp.71-81
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• 2008

Active earth pressure formula, which can consider the effects of ground surface inclination, inclination of inside retaining wall face, wall friction, line load, uniform load, soil cohesion and adhesion, was derived based on the force equilibrium principle. In order to verify the accuracy of this proposed formula, the calculated active earth pressures by the proposed formula were compared with those of graphical solutions. Also, the active earth pressures determined by the proposed formula were compared with those by Coulomb's, Rankine's and Mazindrani's solution under specific conditions. The results matched quite well not only with the graphical solutions but also with those by three other methods. Also, the trend of active earth pressures by the proposed formula were corresponded with results of experimental study by Fang, et al. It can be concluded that this generalized formula not only can overcome the limitations of Rankine's, Coulomb's and Mazindrani's active earth pressure formula but also can consider the external loading conditions.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.262-267
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• 2008

Recently, landslides frequently occur on natural slope and/or man-made cut slope during periods of intense rainfall. With a rapidly increasing population on or near steep terrain, landslides have become one of the most significant natural hazards. Thus, it is necessary to protect people from landslides and to minimize the damage of houses, roads and other facilities. To accomplish this goal, many landslide monitoring systems have been developed throughout the world. In this paper, a simple landslide detection system that enables people to escape the endangered area is introduced. The system is focused on the debris flows which happen frequently during periods of intense rainfall. The system is based on the wireless sensor network (WSN) that is composed of wireless sensor nodes, gateway, and remote server system. Wireless sensor nodes and gateway are deployed by commercially available Microstrain G-Link products. Five wireless sensor nodes and one gateway are installed at the test slope for detecting ground movement. The acceleration and inclination data of test slope can be obtained, which provides a potential to detect landslide. In addition, thresholds to determine whether the test slope is stable or not are suggested by a series of numerical simulations, using geotechnical analysis software package. It is obtained that the alarm should be issued if the x-direction displacement of sensor node is greater than 20mili-meters and the inclination of sensor node is greater than 3 degrees. It is expected that the landslide detection method using wireless senor network can provide early warning where landslides are prone to occur.

• Journal of Korea Water Resources Association
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• v.42 no.11
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• pp.1005-1015
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• 2009

Saltwater intrusion in coastal aquifer was investigated using a laboratory model. Salt-wedge profiles were reproduced in a porous media tank 140 cm long, 70 cm high, and 10 cm wide. The experiments were performed with various conditions of porous media hydraulic conductivity, salinity, and ground surface slope to assess relationships on salt wedge location and inclination. Salt-wedge profiles induced by saltwater intrusion were observed in porous media equilibrium state, and compared with previously derived formulas of the Glover (1959), Henry (1959) and Strack (1976). It was found that salt-wedge shape and formations were affected by the water level ratio ($H_F/H_S$) due to high hydraulic conductivity, saltwater salinity and ground surface slope. High $H_F/H_S$ of porous media having high hydraulic conductivity shifted the saltwater interface toward the saltwater reservoir. Increasing surface slope of the porous media caused the salt-wedge profile inclination to decrease. Saltwater salinity also contributed to the location of saltwater interface, yet the impact was not more significant than hydraulic conductivity.

• Journal of the Korean Geotechnical Society
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• v.30 no.2
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• pp.43-52
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• 2014

This paper examined the effect of step-wise excavation depth on the earth pressure against an excavation wall in rock mass. Numerical parametric studies were conducted based on the Discrete Element Method (DEM) to carry out the problems in rock mass. Controlled parameters included step-wise excavation depth, rock types, and joint conditions (joint shear strength and joint inclination angle). The magnitude and distribution characteristics of the induced earth pressure in a jointed rock mass were investigated and compared with Peck's earth pressure for soil ground. The results showed that the earth pressure against an excavation wall in rock mass were highly affected by different rock and joint conditions, and the effect of step-wise excavation depth increased as a rock type is deteriorated more. In addition, it was found that the earth pressure against an excavation wall in rock mass might be considerably different from Peck's empirical earth pressure for soil ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.199-206
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• 2001

Landslides generally occur due to influences of the internal and external factors. Internal factors include ground characteristics, terrain and so on. External factors can also be divided into natural factors such as rainfall, ground water, earthquake and so on, and artificial factors resulting from cutting and embankments. Among these factors, rainfall becomes the most important external factors by means of which landslides occur in Korea. To appropriately deal with tile effects of pore water pressures due to rainfall, the method using the pore water pressure ratio(r$\_$u/) is generally applied in slope stability analysis or the design of slope reinforcements. Since tire value of r,, is in general not constant over the whole cross section, in most slope stability analyses the average values are used with little loss in accuracy. However, determination of the average values of r$\_$u/ to applied in the design is difficult problem. Therefore, in this study, tile average values of r$\_$u/ according to the intensity of rainfall and slope inclination is suggested based on results of the small scaled model tests using the artificial rainfall apparatus. It is found from the model tests that the average values of r$\_$u/ is about 0.07∼0.18(in case of the intensity of rainfall is 50mm/hr.), about 0.10∼0.28(in case of the intensity of rainfall is 100mm/hr.), and about 0.10∼0.33(in case of the intensity of rainfall is 150mm/hr.).

• Journal of the Korean Institute of Navigation
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• v.5 no.2
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• pp.1-39
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• 1981

A doppler log is the typical device which can measure the ship's speed over the ground directly, by means of doppler effect of the underwater ultrasonic wave, which involves the error due to the sea bottom inclination, the trim and the incorrect transducer installation etc. The present doppler log adopts a single transducer, faced in the direction of themain beam, and therefore it is unable to correct the beam direction to eliminate the above mentioned error. Moreover, the frequencyis also limitted in a comparatively high range for getting a sharp beam with single transducer, and the speed over the ground can not be detectable at the deep sea, for an instance, over 200 meters. This paper describes a theoretical consideration for the doppler log error and an analysis by a computer on the observed speed data by a full size model ship. The result is verified that the most of doppler log error is caused by the ultrasonic beam angle of transducer. To eliminate the doppler log error due to the incorrect transducer installation and also to sharpen the beam for lower frequency range to expand measurable sea depth, this paper proposes a method of controlling the directivity adopting a linear transducer array and of controlling the directivity by the control of exciting current, and investigates by the computer simulation and make experiment with magnetostrictive ferrite transducer of 28, 50 and 75KHz. The experimental results are shown well coincide with the measured ones, and they are revealed that in case where the transducer interval is greater than 1 wavelength, the effective control of the beam direction is hardly performed with keeping adequate beam width and side lobe level. It is concluded that 6-elements array with inter element space of a half wavelength can make comparatively sharp beam and low side lobe level. The results obtained here will contribute very much to the improvement of the performance of doppler log.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.1
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• pp.1-8
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• 2023

In this study, the stability of fishing boat inducing the change of fishing lamp in accordance with the installation of induction lamp in comparison with metal halide lamp was investigated. Inclining test for 8.55 ton class of hair-tail angling fishing boat was performed in order to find a GM and light weight. A stability calculation of the target fishing boat on the basis of KST-SHIP program was evaluated. The stability of the fishing boat with a metal halide lamp such as induction lamp according to the result obtained by the inclining test is slightly different, and the stability is not so much affected. Due to the induction lamp installation, the wind area increased by about 3.178 m². Before installing the induction fishing lamp, G₀M was found to be 0.209 at full load departure and 0.296 at departure from fishing ground. After installing the induction lamp, the full load departure condition is 0.178 and the fishing ground departure condition is 0.260. The G₀M value before and after installation of the induction fishing lamp shows a difference of about 3% at the full load departure condition. The value of the critical angle of inclination definition showed a difference of about 16%. Despite these differences, it is lower than the regulations; it was confirmed that there will be no significant difference unless it is in an overloaded state.