• Smart Structures and Systems
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• v.34 no.1
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• pp.41-50
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• 2024

The accurate measurement of temperature in the ground source heat pump system is crucial for assessing the thermal response of the system and validating the numerical model for parametric study, which is necessary for the thermal performance evaluation of the geothermal energy system. Conventional temperature sensors have some disadvantages such as they are difficult to install, and their position can be shifted during the backfill process of the ground heat exchanger. In this study, Fiber Bragg Grating (FBG) sensors were used to measure the temperature change of a recently developed ground heat exchanger (Coil Column Unit, CCU). FBG sensors were first calibrated in a thermal chamber alongside a correlation sensor (RTD sensor). The calibrated sensors were then mounted on the pipe surface at each spiral of the CCU to measure how temperature changes during the in-door mockup thermal response test. Finally, the measurement results of the FBG sensors were verified with a finite element coded program. The results indicated that the temperature difference between the numerical analysis and the experiment was less than 1%, which is significantly lower than that of the previous study using the RTD sensors. Therefore, it is feasible to apply FBG sensors for temperature measurement during the operation of the TRT of the geothermal energy system.

• Journal of the Korean Geotechnical Society
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• v.35 no.5
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• pp.21-30
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• 2019

While the study of the shallow tunnel has been mainly on the longitudinal load transfer and horizontal surface conditions, the study of the ground behavior of shallow tunnel under the slope is not sufficient. Therefore, in this study on the ground behavior around a tunnel due to the sidewall deformation of shallow tunnel under the slope that is excavated in longitudinal direction, a scale-down model test has been performed. The model tunnel has the dimension of 320 mm wide, 210 mm high and 55 mm long with enough material strength in aluminum and the model ground has the uniform ground conditions by 3 types of carbon rods. The model test has been performed with the variables of slopes and the cover depths by controlling the tunnel sidewall deformation, and the change of sidewall-load, load transfer, ground subsidence was monitored and analyzed. According to the increase of the slope, the maximum ground subsidence increased by 20~39% compared to the horizontal surface. The load ratio increased by maximum 20% in the tunnel crown and decreased in sidewall according to the surface slope. The load transfer shows maximum 128% of increase at the cover depth of 1.0D, while at the 1.5D cover depth it shows non-critical difference from horizontal surface. The slope has major effects on load transfer at the cover depth of 1.0D.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1224-1231
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• 2009

1D Analysis have been using Design of SCP in order to improve the soft ground. But 2D Analysis is researching and developing to get more accurate results. Using 2D Analysis, suitable Numerical Analysis Model should be selected and be tested in many situations. In this study, Laboratory Model Tests are analyzed by Numerical Analysis Method. After selecting Numerical Analysis Model, it is being tested many conditions.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.117-128
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• 2000

Sand compaction pile(SCP) is one of the ground improvement techniques which is being used for not only accelerating consolidation but also increasing bearing capacity of loose sands or soft clay grounds. In this study, laboratory model test and large-scale direct shear test were performed to investigate the effects of area replacement ratio of composite ground in order to find out the optimum value of area replacement ratio for the ground improvement purpose. Area replacement ratios of 20%, 30%, 40%, 50%, 60% were chosen respectively in the model tests to study the effects of area replacement ratio on variations of stress concentration ratio, settlement and shear strength characteristics of composite ground. In large-scale direct she4ar tests, area replacement ratios of 20%, 30%, 46% were applied to study their effects on shear strength characteristics of composite ground.

• Journal of the Korean Geosynthetics Society
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• v.10 no.1
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• pp.43-51
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• 2011

Pile-supported embankment is one of the reinforcing methods to minimize damage due to the severe subsidence and lateral flow when soft clay ground is supported with embankment. pile-supported embankment mainly penetrates soft ground into the bearing stratum in order to support surcharge load which minimizes the subsidence and lateral flow due to the surcharge load. The aim of this research is to review quantitatively reinforcing effect of pile-supported embankment which is installed in soft clay ground. From the model test, it reproduced the ground movement with regard to the non-reinforced and reinforcing embankment-pile and also analyzed stabilizing effects of lateral flow due to the pile-supported embankment. With regard to the case of installing pile-supported embankment, its were analyzed stabilizing effects of lateral flow in cases of quick-load and slow-load to make different surcharge load.

• Journal of the Korean GEO-environmental Society
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• v.24 no.11
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• pp.19-24
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• 2023

Ground anchor has been widely used specially for maintaining stability on reinforced cut slope in expressway. While the durability of the ground anchors should be ensured over the service life. However, the long-term loss of tensile force has occurred in most of field-installed anchors. Main causes are not clearly identified and very few studies have been made for analyzing long-term behavior of ground anchor in slopes. In this study, full-scale model tests and long-term measurements were made to obtain the load-displacement data and identified the causes of the long-term behaviors of ground anchor. As a result, the bond strength decreases exponentially with increasing water-binder ratio. Especially, groundwater is the most influencing factor to the bond strength. In the long-term behavior, the load decreases sharply until the initial settlement stabilized, and thereafter the tension force decreases constantly.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.15-23
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• 2023

The grouting method is a method of construction for the purpose of waterproofing and reinforcing soft ground. When grout is injected into the ground, there are various types of penetration and diffusion of grout depending on the shape of the ground, the size of soil, the porosity, and the presence or absence of groundwater. the current situation. Therefore, in this study, to investigate the penetration performance of the grouting to conductive material, laboratory tests were performed on the addition of the conductive material. In the injection test, 0%, 3%, and 5% of the mixed water were added as conductive materials to the grout, and the original ground condition was composed of various types of ground composed of gravel and silica sand. Conductive grout is injected by pressure into the model ground using a dedicated injection device, and the injection time (t), pressure (p), flow rate (v) and injection amount (q) are measured, and the hardened body injected in the model ground is collected. Penetration performance was evaluated. In the results of the grout injection experiment, the amount of conductive material used and the grout injection rate showed an inverse relationship, and it was confirmed that the penetration pattern was changed according to the size of the soil particles in the model ground. The grout containing the conductive material has relatively good penetration into the ground and excellent strength and durability of the hardened body, so it was judged that it could be used as an additive for measuring the penetration range of the grout.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.2
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• pp.1-12
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• 2024

In order to integrate two consolidation theories of Terzaghi's consolidation theory and Mesri's secondary compression theory and to identify a model suitable for analyzing stress-strain behavior over time, numerical analysis on consolidation tests were conducted using a modified cam-clay model and a soft soil creep model and the following conclusions were obtained. The results of numerical analysis applying the theory that a linear proportional relationship is established between the void ratio at logarithmic scale and the permeability coefficient at logarithmic scale is better agreement with the result of oedometer test than the results of applying constant hydraulic conductivity. The modified cam-clay model is a model that does not include secondary compression, but the slope of the normal consolidation line corresponding to the compression index of the standard consolidation test includes secondary compression, so the actual settlement curve over time is lower than the predicted value through numerical analysis. It always gets smaller. Other previous studies that applied Terzaghi's consolidation theory to consolidation test analysis showed the same results and were cross-confirmed. The soft soil creep model, which includes secondary compression in the theory, showed good agreement in all sections including secondary compression in the consolidation test results. It was judged appropriate to use a soft soil creep model when performing numerical analysis of soft clay ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.82-89
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• 2004

To secure stability and availability of Rammed Aggregate Pier method as the foundation of a structure, the shear strength characteristics according to the area replacement ratio of RAP and the relative density of in-situ ground was studied through soil laboratory tests and large direct shear tests in a model ground. As a result, the internal friction angle tends to increase in proportion to in-situ relative density(Very Loose, Loose, Medium) in composite ground formed by the same area replacement ratio of RAP and also increase in proportion to increasing the area replacement ratio(30, 40, 50%) of RAP in the same ground condition. Furthermore, the comparative analysis between the experimental value and theoretical value of the shear strength is carried out.

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.61-72
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• 2002

In this study, model tests were performed to evaluate the injection characteristics of cement grouting which was used as waterproof method for leakage of underground structures. To simulate in situ condition, model tests were performed with varying the ground conditions such as the kinds of test soils, soil density, water content, etc. and the injection conditions such as kinds of injection materials, injection pressure, injection quantity, injection velocity, etc. From the results of model tests, the major factors influencing the permeability of injection material were determined to be the kinds of soils and soil density. To obtain optimal injection effects, injection should be performed after investigating the condition of backside ground accurately.