• Journal of Korea Water Resources Association
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• v.38 no.1
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• pp.73-82
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• 2005

A soil moisture measuring method of a hillslope for Korean watershed is developed to configure spatial-temporal distribution of soil moisture. Intensive surveying of topography had been performed to make a digital elevation model(DEM). Flow distribution algorithms were applied and a distribution pattern of the measurement sensors was determined to maximize representative features of spatial variation of soil moisture. Inverse surveying provides appropriate information to install the waveguides in the field. Measurements were performed at the right side hillslope of Bumrunsa located at the Sulmachun watershed. A multiplex monitoring system has been established and spatial-temporal variation of soil moisture data has been measured for a rainfall-runoff event. Acquired soil moisture data show that physical hydrologic interpretations as well as the effectiveness of monitoring system. Lack of connectivity in vertical distribution of soil moisture suggests that preferential flow and macropore flux are important components in the hillslope hydrology.

• Journal of Forest and Environmental Science
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• v.7 no.1
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• pp.35-41
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• 1990

This study was conducted to find out the suitable gradient and length of the slope from the landslide of banking slope and cutting slope caused by rainfall. The survey was carried out on forest road built in 1986. And the period of survey was from June, 1989 to August, 1989 after dividing the forest road into A and B. The survey plots consisted of the 12 banking slopes and 6 cutting slopes. The results obtained from the study were summarized as follows; 1. The rate of landslide appeared 75% in A forest road, 50% in B forest road, and then the average 67% in A and B forest road. But the value of landslide showed considerably low. 2. Because of landslide chiefly occuring on banking slope of $36^{\circ}{\sim}38^{\circ}$ and on cutting slope of $42^{\circ}{\sim}43^{\circ}$, it is suitable to decide the banking slope and cutting slope below each $36^{\circ}$ and $40^{\circ}$. 3. Landslide was the same on banking slopes through the length of slope. The best suitable length of slope is below 4m in cutting slope.

• Journal of Korea Water Resources Association
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• v.37 no.1
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• pp.31-41
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• 2004

A soil moisture measuring method of hillslope for Korean watershed is developed to configure spatial-temporal distribution of soil moisture. Intensive surveying of topography had been performed to make a digital elevation model(DEM). Flow distribution algorithms were applied and a measurement system was established to maximize representative features of spatial variation. Soil moisture contribution mechanisms of rainfall-runoff process have been derived. Measurements were performed at the right side hillslope of Buprunsa located at the Sulmachun watershed. A Multiplex system has been operated and spatial-temporal soil moisture data have been acquired. Relatively high correlation relationship between flow distribution algorithm and measurement data can be found on the condition of high humidity.

• Progress in Medical Physics
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• v.12 no.1
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• pp.71-77
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• 2001

The region, near the edge of a radiation beam, where the dose changes rapidly according to the distance from the beam axis is known as the penumbra. There is a sharp dose gradient zone even in megavoltage photon beams due to source size, collimator, lead alloy block, other accessories, and internal scatter ray. We investigate dosimetric characteristics on penumbra regions of a standard collimator and compare to those of theoritical model for the optimal use of the system in radiotherapy. Peripheral dose distribution of 6 W Photon beams represents penumbral forming function as the depth. Also we have discussed that the peripheral dose distribution of clinical photon beams, differences between calculation dose use of emperical penumbral forming function and measurements in penumbral region. Predictions by emperical penumbral forming functions are compared with measurements in 3-dimensional water phantom and it is shown that the method is capable of reproduceing the measured peripheral dose values usually to within the statistical uncertainties of the data. The semiconductor detector and ion chamber were positioned at a dmax depth, 5cm depth, 10cm depth, and its specific ratio was determined using a scanning data. The effective penumbra, the distance from 80% to 20% isodose lines were analyzed as a function of the distance. The extent of penumbra will also expand with depth increase. Difference of measurement value and model functions value according to character of the detector show small error in dose distribution of the peripheral dose.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.85-90
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• 1988

A probabilistic model for the failure in a homogeneous soil slope is presented. The Safety of the slope is measured through its probability of failure rather than the customary factor of safety. The safety margin of slope failure is assumed to follow a normal distribution. Sources of uncertainties affecting characterization of soil property in a homogeneous soil layer include inherent spatial variability., estimation error from insufficient samples, and measurement errors. Uncertainties of the shear strength-along potential failure surface are expressed by one-dimensional random field models. The rupture surface, created at toe of a soil slope, has been considered to propagate towards the boundary along a path following an exponential (log-spiral) law. Having derived the statistical characteristics of the rupture surface and of the forces which act along it, the probability of failure of the slope was found. Finally the developed procedure has been applied in a case study to yield the reliability of a soil slope.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.105-111
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• 2010

This study is to consider applicability of spiral bolt strain gauge as an instrument measuring behavior of soft ground foundation and rock slope. When the instrument was installed on the ground, it can be useful to identify the state of ground behavior because it has the characteristics of flexibility, as well as to apply the ground reinforcement because it has higher pull-out resistance to the ground. From the measurement of behavior to soft ground foundation, the strain shows a stable state in the beginning, then was observed significant change in the upper and the middle of spiral bolt strain gauge after 400 days. This is analyzed that ground loosening, which is due to occurred frequent earthquake of magnitude 1~2 with increased rainfall, lead to the instability of the ground. From the measurement of behavior to rock slope, the strain shows a stable state with very little change in a period of 0~50 days and the biggest strain at 4.2 m (P6) in a period of 50~100 days, then other places except P6 was maintained at a stable state in a period of 100~160 days. The reason is analyzed because that blasting for excavated limestone surrounding was affected to the largest at P6. However, based on the size of strain change by behavior of the soft ground foundation and rock slope, it is considered that the present condition are not effected on stability of retaining structure and rock slope. In conclusion, the proposed spiral bolt strain gauge can be useful to measure behavior of soft ground foundation and rock slope, and also to be measured behavior as well as reinforcement of the target ground.

• Progress in Medical Physics
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• v.25 no.4
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• pp.255-263
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• 2014

The dosimetry of very small fields is challenging for several reasons including a lack of lateral electronic equilibrium, large dose gradients, and the size of detector in respect to the field size. The objective of this work was to evaluate the suitability of a new commercial synthetic diamond detector, namely, the PTW 60019 microDiamond, for the small field dosimetry in cyberknife photon beams of 6 different collimator size (from 5 mm to 30 mm). Measurements included dose linearity, dose rate dependence, output factors (OF), percentage depth doses (PDD) and off center ratio (OCR). The results were compared to those of pinpoint ionization chamber, diamond detector, microLion liquid Ionization chamber and diode detector. The dose linearity results for the microDiamond detector showed good linearly proportional to dose. The microDiamond detector showed little dose rate dependency throughout the range of 100~600 MU/min, while microLion liquid Ionization chamber showed a significant discrepancy of approximately 5.8%. The OF measured with microDiamond detector agreed within 3.8% with those measured with diode. PDD curves measured with silicon diode and diamond detector agreed well for all the field sizes. In particular, slightly sharper penumbras are obtained by the microDiamond detector, indicating a good spatial resolution. The results obtained confirm that the new PTW 60019 microDiamond detector is suitable candidate for application in small radiation fields dosimetry.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.33-39
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• 2015

Recently, the event of slope failure has been occurring frequently due to rapid climate changes and broad development of infrastructures, and the research for establishment of monitoring and prevention system has been an attentive issue. The major influence factors of slope failure mechanism can be considered moisture and temperature in soil, and the slope failure can be monitored and predicted through the trend of moisture-temperature change. Therefore, the combined sensing technology for the continuous measurement of moisture-temperature with different soil depths is needed for the slope monitoring system. The various independent sensors for each item (i.e. temperature and moisture respectively) have been developed, however, the research for development of combined sensing system has been hardly carried out. In this study, the high-fidelity sensor combing temperature-moisture measurement by using the minimized current consuming temperature circuit and the microwave emission moisture sensor is developed and applied on the slope failure monitoring system. The feasibility of developed monitoring system is verified by various experimental approaches such as standard performance test, mockup test and long-term field test. As a result, the developed temperature-moisture combined measurement system is verified to be measuring and monitoring the temperature and moisture in soil accurately.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.4
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• pp.233-237
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• 2003

This study was conducted to provide a rational forest management method for a natural oak (Quercus variavilis) forest stand in the central part of South Korea based on characteristics of growth and water relation parameters. Average volume per hectare was 175.1 ㎥ in the study site of oak stands. Basal area and volume of each direction appeared to increase as the slope direction moves from north to south, but annual mean increment and periodic annual increment of DBH for 10 years showed the lowest value at the southern aspect. Maximum water potentials measured between 12 and 14 o'clock were analyzed by direction and elevation in the oak stands. Water potential of oak decreased as the slope changed from the north to the south aspect and water potential increased at lower elevations. Soil water content for the oak stands tended to decrease as the aspect shifted from north to south. Water potential and soil moisture content were highly correlated. It appears that oaks have a higher moisture requirement at the southern aspect, because of stand density related to intraspecific competition.

• Journal of the Korean Geotechnical Society
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• v.37 no.7
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• pp.5-12
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• 2021

When drilling investigations for Rock Slopes are not possible, it is often difficult to calculate the Ground Design Constants required for the Limit Equilibrium Analysis. Therefore, the outcrops or partially cutted Rock Slopes were analysed using JRC and JCS that can be easily and conveniently measured. In particular, the effect of the JRC on the Safety Factor or the Rock Slopes was analyzed intensively, and the results were presented as a relationship formula and Table. When the Rock slope was stable, the JRC increased by an average of 9.0% as the slope height increased, and increased by an average of 29.8% as the slope angle increased. JRC was more sensitive to slope angle changes. The Cohesion corresponding to JRC was calculated from JRC-Fs formula. JRC and Cohesion showed a nonlinear relationship, and the Cohesion was about 8.0% more sensitive to slope height changes than slope angle changes.