• Journal of the Korean Professional Engineers Association
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• v.25 no.4
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• pp.102-108
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• 1992

This study was carried to find out the soil characteristics of landslide site and to develope landslide prediction method by seismic refraction prospecting. For these aims, landslide condition and travel time were investigated at 68 Landslide sites over the country during 1990 to 1991. The results were as follows. 1. The surface of rupture was included mainly in C layer. Its Hardness was less than 3kg / $\textrm{cm}^2$ at the upper pare of landslide. 2. When the profile line length was 20m, the range of travel time was 40 to 90 msec. The travel time did not differ between bedrocks. 3. Refraction distance ranged from 1 to 7m and mean of that was 2.5m. Travel time was increased according to receiving distance without large variance in the refraction distance but that was appeared large variance out of the refraction distance on slope that has shallow soil depth and discontinuous ground surface. Therefore, the spread distance must be shorten to 10-l5m. 4. The seismic velocity at the first layer(layer of rupture) was less than 500m1sec by degree of weathering and the velocity at the second layer decreased in order of Granite> Granitic gneiss >Sedimentary rock. 5. The first layer observed by seismic refraction was contained C layer that has parent material and weathered rocks of hardness 10-20kg/$\textrm{cm}^2$. 6. Among the range of seismic velocity was less than 200m/sec in 63% of the total plots, 200-300m/sec in 34% and 300-500m /sec in 3%. 7. There was a proportional relationship between seismic prospecting soil depth and executive soil depth, and seismic propection soil depth was about 10 to 20cm deeper than the order.

• Geomechanics and Engineering
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• v.9 no.5
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• pp.585-599
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• 2015

Laboratory model tests were conducted to investigate the effect of surcharge loading rate on the magnitude of lateral displacement of prefabricated vertical drains (PVDs) improved deposit. The test results indicate that under the condition that the system had sufficient factor of safety (FS) ($FS{\geq}1.2$), for the similar model ground under the same total applied surcharge load, the lateral displacement increases with the increase of loading rate. The test results have been used to check the validity of a previously proposed method for predicting the maximum lateral displacement, and it shows that the data points are around the middle line of the predicted range, which supports the usefulness of the proposed method. The basic idea of the prediction method is an empirical relationship between the normalized lateral displacement (NLD) and a ration of load to the undrained shear strength of the deposit (RLS). The model test results offer some modifications of the NLD-RLS relationship: (1) instead of a bilinear relationship, NLD-RLS relationship may be entirely nonlinear; (2) the upper bound value of RLS for the proposed method can be used may be limited to 2.1 instead of the originally proposed value of 3.0.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1342-1351
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• 2011

Nowadays rolling stock has become a fast and convenient transportation and increased in its demands. But the improvement of speed has result in increase of aerodynamic noise and therefore residential districts near by the railroad are now constantly suffering from the racket. Thus the study regarding rolling stock's environmental noise measurement and appraisal has become important. The case of environmental noise, there are no changes of tone so prediction can be made by reducing areas around the railway. This is part of the study which estimates the noise around the railway using scaled model, and the source of the noise has been researched on. The scaled model of rolling stock will have to be able to make high frequency and it needs to be spread out in a short amount of time. When popping a balloon or firing a gun fits its condition and this study analyzed the characteristics of these two different noises. Measurement was held on a wide vacant lot and the reflection effect of the ground is additionally examined. It is judged to be used in the future when predicting the environmental noise of railway vehicles.

• Journal of Environmental Impact Assessment
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• v.21 no.2
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• pp.289-296
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• 2012

The shock vibration such as machine vibration, blasting vibration etc. has effect on nearby structure as well as human body. The purpose of this study is to predict allowable limit distance of vibration about human body. First of all, vibration velocity such as PPV, PVS was measured by shock vibration experiment, and vibration level was calculated by conversion formula of vibration velocity. And then, allowable limit distance was analyzed by converted vibration level. The results are as follows : Firstly, the correlation coefficient of converted vibration level was over R=0.94, and vibration level caused by PVS was usually represented to high curve line. Secondly, the cross point of vibration level between ground and concrete condition was represented to 66.68dB(V), and allowable limit distance was represented to difference over three times when vibration regulation was raised from 65dB(V) to 80dB(V).

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.1-7
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• 2014

A set of preliminary design parameters for the bipropellant rocket engine using liquid methane-fuel as green propellant were derived through a theoretical performance analysis. Chemical equilibrium analysis utilizing CEA was conducted for the prediction of combustion performance: combustion characteristics according to the O/F ratio and chamber pressure variation were investigated. For a determination of chamber-characteristic length, the vaporization time of fuel-droplet with various performance parameters was calculated by applying Spalding's 1-D droplet vaporization model. Finally, the preliminary design specification of methane-bipropellant rocket engine, which is to be performance-tested under the ground firing condition, was proposed.

• Journal of Biosystems Engineering
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• v.25 no.3
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• pp.195-202
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• 2000

This study was conducted to recognize a possibility that cone index can be used as a means of evaluating the tillage workability. Cone indexes were measured every 24 hours after rainfall at the experimental plots, and the rotary and plowing operations were conducted at the same time. The workability was evaluated on a basis of three categories of good, fair and poor depending on the quality of the performed works. Although the workability was affected by many factors such as soil type, moisture content ground slope and weather condition, the duration and amount of rainfall were of most influence. Results of the study showed that a good workability was resulted from the cone indexes greater than an average of 552 kPa for rotary operations and 671 kPa for plowing operations. Fair work was obtained with cone indexes greater than an average of 331 kPa for rotary operations and 459 kPa for plowing operations. The cone indexes less than an average of 171 kPa and 149 kPa resulted in poor workabilities for rotary and plowing operations, respectively. The experimental results may provide a general guideline for evaluating the tillage workability by cone index.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.214-220
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• 2003

Pipe jacking is a name for a method to excavate a tunnel by pushing pipe into the ground from an especial pit. Size of tunnels in this method is different from under 900mm (microtunneling) to more than 3,000mm. Method of excavation is also different from hand digging to use of any kind of tunnel boring machines such as slurry and earth pressure balance (EPB) machines. Slurry pipe jacking was firmly established as a special method for the nondisruptive construction of the underground tunnels in urban area. During the pipe jacking and microtunneling process, the jacking load is an important parameter, controlling the pipe wall thickness, need to and location of intermediate jacking station, selection of jacking frame and lubrication requirements. The main component of the jacking load is due to frictional resistance. In this paper the skin friction between pipe surface and surrounding condition also lubricant quality based on a few fundamental tests, were considered. During this study unconfined compressive strength test, dynamic friction measurement test and direct shear box test were raised for one of the largest diameter slurry pipe jacking project in Fujisawa city in Japan. It could be concluded that in slurry pipe jacking, prediction of frictional forces are mainly dependent on successful lubrication, its quality and lubricant strength parameters. Conclusions from this study can be used for the same experiences.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.839-848
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• 2011

TBM (Tunnel Boring Machine) tunnel should be carry out with the adopted machine until the end of excavation because of impossibility of replacement or modification of machine. Observation of the face of the tunnel is difficult, especially in EPB(Earth Pressure Balance) shield TBM, predict changes in the ground condition with analyzing data, collected during the excavation, and it should be reflected in construction. Until recently, subjects of studies on TBM are mainly the determination of machine and the development of advance rate prediction model, according to the characteristics of ground which is the target of excavation. However, study focused on the estimation of ground conditions and the improvement in operational methods using excavation data of TBM equipment, the principal of the excavation, has been done not so much. This study examine the variances in advance rate depending on changes in operating conditions and evaluate the optimal operating conditions of adopt machine, using working data obtained from EPB shield TBM project. The result of this study is suggested as follows. First, cutter head RPM and total thrust force are biggest influences on advance rate, Second, it is recommended for proper advance rate that total thrust force is controlled while optimum cutter head RPM is kept, Third, according to the increasing trend of total thrust force, the changes in ground conditions can be predicted, the appropriate operating conditions can be determined.

• Fire Science and Engineering
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• v.24 no.4
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• pp.18-26
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• 2010

The change of fuel moisture according to the passed days after a raindrop is very important to forecast risk of forest fire and to make a good use of forest fire watchmen. For that reason, in the Spring of 2007, we researched pine forest that were widespread growing in Yeongdong region to find out the condition of forest fire risk. We developed the forecast model of fuel moisture change on dead tree branches which were dropped on the ground and less than 0.6 cm, 0.6~3.0 cm, 3.0~6.0 cm, and more than 6.0 cm in diameter after more than 5.0 mm in precipitation. The result showed that the less diameter of ground fuel and small stand of pines the faster diminishing of fuel moisture, and the days of reaching to a forest fire danger fuel moisture level were represented by two (2) days for less than 0.6 cm diameter of small stand of pine and three (3) days for 0.6~3.0 cm diameter one, respectively. By those results, we developed the forecast model($R^2=0.76{\sim}0.92$) of fuel moisture change on different diameter of small stand of pine, and found that the model had statistical significant of 1% level after we applied it to the data of 2008 after the same period of raindrop by actual meteorological measurement.

• Tunnel and Underground Space
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• v.15 no.2 s.55
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• pp.111-118
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• 2005

The area of investigation belongs to Okchon metamorphic zone and the fault fractured zone runs parallel to the tunnel direction. It causes the independent decline of tunnel face and the slackness of the tunnel surrounding base so, after all, the severe displacement has occurred within the tunnel. Accordingly, the TSP(Tunnel Seismic Prediction) survey has been performed to investigate the extent of fault fractured zone and to analize its characteristics. Also, we have analized the behavior causes by performing the tunnel face mapping and drilling investigation, and confirmed the position and scale of geological anomaly area and front fractured zone which influences tunnel excavation and supporting. Collected data analyzed ground layer condition through 3 dimensional modeling. Several variables included in the modeling were analyzed by geostastistics. The analysis of the modeling data shows that the belt of weathering by fault fractured zone is developing on the basis of the right side of tunnel and that is decreasing to the left side. The fault fractured zone was confirmed that it has strike, $N0\~5^{\circ}E$ dip NW, and it is consisted of large-scale fractured zone including several anomalies. The severe displacement in tunnel is probably caused by asymmetrical load that n generated by the crossing of discontinuity and the rock strength imbalance of tunnel's both side by fault fractured zone, and judge that need tunnel reinforcement method of grouting etc.