• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.5-19
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• 2017

This study has been conducted to improve the conventional compaction management method by measuring the water content and dry unit weight of soil using the Time Domain Reflectometry (TDR) method. In order to verify the measured value of the developed flat TDR system, laboratory tests were conducted on six soils. Also, based on laboratory experiments, field tests were conducted to evaluate the applicability of the developed flat TDR system. Also, a comparison experiment was conducted with the Purdue TDR system. In addition, FE analysis was done to confirm the influence range of the Flat probe. As a result, it was confirmed that the influence range was about 10 cm. As a result of laboratory experiment, the water content ratio showed an error of about 0.4% on the average, and in the case of dry unit weight, it showed an error of about 1.6%. For the field test, the water content ratio and unit weight showed an error of 0.8% and 2.5%, respectively. Through the experimental results, it was confirmed that the measured value of the Flat TDR system is more accurate than that of the conventional TDR system.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.333-342
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• 2021

In this study was conducted to measure the water content and dry unit weight of the ground using TDR (Time Domain Reflectometry) in order to supplement the problems of the conventional compaction management method. The Flat TDR system is a device that does not cause ground disturbance, and in order to verify the measured values, the dry density and water content were measured for samples of the ground subject at 7 sites other than Jumunjin Standard Temple. The water content section was divided into 6 sections of 3, 6, 9, 12, 15, and 18%, and the experimental results were confirmed according to the unified classification method. As a result of the indoor experiment, the water content showed an error of about 0.7% for the SP sample and about 1.3% for the SM sample. In addition, the dry unit weight confirmed an error of about 7% for the SP sample and about 5% for the SM sample. It was confirmed that stable values were derived in sandy or silty sandy ground except for clay or gravel. Through the experimental results, it was confirmed that the measured values of the flat TDR system derive similar values to the existing traditional compaction management method, and it was determined that the flat TDR equipment was suitable for construction sites that require quick constructability and economic feasibility.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.173-191
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• 2022

In this study, the shear wave velocity of the ground was measured using Flat TDR, and the precision analysis of the measured value and the verification of field applicability were performed. The shear wave velocity measurement value was derived in the field using the piezo-stack combined in the Flat TDR. analyzed. As a result of the experiment, the average value of the change in shear wave speed at the time of grout material injection was 10.15 m/s at the beginning of age, and the average value of the change in shear wave speed after the 7th to 14th days was 65.99 m/s, showing a tendency to increase with age. Also, it was found that dry density and shear wave speed increased as the water content increased on the dry side, and that the dry density and shear wave rate decreased as the water content increased on the wet side as the water content increased. The shear modulus value derived from the field test was confirmed to be a minimum of 17.36 MPa and a maximum of 28.13 MPa, confirming a measurement value similar to the reference value. Through this, it can be seen that the measured value of the shear modulus using Flat TDR is reliable data, and it can be determined that the compaction management of the site can be effectively managed in the future.

• Journal of the Korean Geotechnical Society
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• v.32 no.4
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• pp.51-61
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• 2016

In this study, a new TDR system equipped with a flat type probe has been developed to improve the currently used TDR system that measures dry density and water content. To verify the developed TDR system, TDR tests were conducted on Jumunjin sand and three typical soils. Also, additional tests were performed to measure the correction value of the developed probe. Using the TDR signals, dielectric constant, electrical conductivity and soil constants were derived. The water content and dry density of the soils were determined through the TDR tests. The applicability of the TDR system was examined by comparison of the measured values by TDR and the real values. The values of dry density and water content were found to have about 2% and 0.5% error, respectively. Based on the test results, it has been confirmed that the new TDR system can be used as an alternative to the previous TDR system as it can measure the dry density and the water content with reasonable accuracy, leading to significant time and cost savings.

• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.77-85
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• 2016

This study was conducted to solve the problem such as damage of completed compaction ground using the conventional compaction control method. In this study, a TDR system equipped with a flat type probe has been developed. Also, the Piezoelectric stack, which is an instrument for measuring the elastic wave on the ground, has been added to the developed flat type probe. In this study, the strength variation of reinforced soil with time was determined by using the TDR system. The value of compression and shear modulus increased from 198.65MPa to 541.80MPa and from 125.55MPa to 302.02MPa with time, respectively. Based on the test results, it has been confirmed that the developed TDR system can be used as reinforced effect analysis of soil and compaction control.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.1
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• pp.21-30
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• 2018

In this study, we developed the Soil Moisture Data Assimilation (SMDA) scheme to extract Effective Soil Characteristics-ESC (Sand, Silt, Clay %) from MODerate resolution Imaging Spectroradiometer (MODIS) products. The SMDA scheme was applied to the MODIS-based Soil Moisture (SM) data during the summer (July to September) period. Then the ESC and soil erosion factors (K) were predicted, respectively. Several numerical experiments were conducted to test the performance of SMDA at the study sites under the synthetic and field validation conditions. In the synthetic experiment, the estimated soil moistures values(R: >0.990 and RMSE: <0.005) were identified well with the synthetic observations. The field validation results at the Bangdongri and Chungmicheon sites were also comparable to the TDR-based measurements with the statistics (R: 0.772/0.000 and RMSE: 0.065/0.000). The estimated ESC values were also matched well with the measurements for the synthetic and field validation conditions. Then we tested the SMDA scheme to extract the ESC from the MODIS-based soil moisture products. Although uncertainties exist in the results, the estimated soil moisture and ESC based on the SMDA were comparable to the measurements. Overall, the K factors were similarly distributed based on the derived ESC. Also, the K factors in the mountainous regions were higher than those of the relatively flat areas. Thus, the newly developed SMDA scheme can be useful to estimate spatially and temporally-distributed soil erosion and establish soil erosion management plans.