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Lee C.,Geotechnical Engineering Research Institute | Park S.,Korea University | Choi H.-J.,Korea University | Lee I.-M.,Korea University | Choi H.,Korea University
Tunnelling and Underground Space Technology | Year: 2016

A novel textile-type ground heat exchanger, a so-called "energy textile", is introduced in this paper. The energy textile to be assembled in a tunnel lining is devised to function as a ground-coupled heat exchanger (GHE) to operate a ground source heat pump (GSHP) system in tunnels. A test bed of six pilot energy textile modules with various configurations was constructed in an abandoned railroad tunnel in South Korea. Long-term field monitoring was performed to measure the heat exchange capacity of each energy textile module by applying artificial heating and cooling loads on it. In the course of monitoring, the inlet and outlet fluid temperatures of the energy textile, the pumping rate, the ground temperature, and the air temperature inside the tunnel were measured continuously. Each type of energy textile modules was compared in terms of its heat exchange efficiency, which appears to be sensitive to fluctuation of air temperature in the tunnel. In addition, three-dimensional computational fluid dynamic (CFD) analyses were carried out, employing FLUENT, to simulate the field test for each energy textile module. After verification of the numerical model with the field measurement, the influence of a drainage layer on the performance of the energy textile was parametrically examined. A conventional design procedure for horizontal GHEs was used in a preliminary design of an energy textile module, taking into consideration the air temperature variation inside the tunnel over the course of one year. © 2016 Elsevier Ltd.

Mok Y.J.,Kyung Hee University | Park C.S.,Geotechnical Engineering Research Institute | Nam B.H.,University of Central Florida
Soil Dynamics and Earthquake Engineering | Year: 2016

A borehole seismic source was developed to measure horizontally-polarized shear (SH-) waves in the near surface and to improve drawbacks of conventional seismic sources. An electro-mechanical-type source, called "TahcBalm", has exceptional repeatability in generating signature SH-waves, while being sufficiently small and light to be fitted in 76 mm diameter cased or uncased boreholes. The source has been extensively used for borehole seismic testing at various locations with diverse soil and rock conditions. The cross-hole and in-hole testing signals are strong enough and allow the clear identification of the first arrival of SH-waves in all tested geologic environments. TahcBalm generates SH-waves with proper wavelength of about 1 m and 0.5 m for cross-hole and in-hole testing configurations respectively, at soil and rock sites. The source performs well in terms of data quality and ease of use. © 2015 Elsevier Ltd.

Hung L.C.,Dong - A University | Nguyen T.D.,Dong - A University | Lee J.-H.,Geotechnical Engineering Research Institute | Kim S.-R.,Dong - A University
Acta Geotechnica | Year: 2015

This paper presents a study on applicability of predicting toe bearing capacities from cone penetration test (CPT) for PHC (pretensioned spun high-strength concrete) driven piles into deep sandy deposits in the Nakdong River deltaic area west of Busan City in South Korea. Using toe bearing capacities obtained from pile driving analyzer (PDA) tests as reference values, which were reliably calibrated by on-site O-cell tests, the applicability of the CPT-based methods was evaluated using a statistical rank index (RI). A total of 82 piezocone penetration test soundings and 190 PDA test piles were used for reliability analysis in this study. Three correction steps were applied to obtain reliable PDA and CPT data sets before ranking is carried out. The RI index is combined from four criteria: (1) the best-fit line, (2) the arithmetic mean and standard deviation, (3) the cumulative probabilities, and (4) the log-normal and histogram distributions. Based on these criteria the performance of some SPT-based methods in the literature is evaluated. © 2015 Springer-Verlag Berlin Heidelberg

Park J.H.,Geotechnical Engineering Research Institute | Chung M.,Geotechnical Engineering Research Institute | Huh J.,Chonnam National University
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015

For the implementation of the LRFD in practice, a case study on an actual bridge foundation design using both the ASD and the LRFD is comprehensively conducted. The bridge considered in this study is a 5-span (230m long span length) and, 464m-long concrete cable-stayed girder bridge, which foundation consists of drilled shafts socketed in weathered rock. The Bayesian theory was implemented to update distributions of resistances followed by the resistance factors. The result showed that the LRFD method can contribute to economical foundation designs guaranteeing the probabilities of foundation failure do not exceed the quantitative target failure probability. Furthermore, Bayesian-implemented LRFD was found to give more cost-savings than non-Bayesian LRFD by reducing margins of safety. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).

Chang I.,Geotechnical Engineering Research Institute | Prasidhi A.K.,Samsung | Im J.,Korea Advanced Institute of Science and Technology | Shin H.-D.,Georgia Institute of Technology | Cho G.-C.,Korea Advanced Institute of Science and Technology
Geoderma | Year: 2015

Desertification and soil degradation are becoming more serious due to global warming and concurrent extreme climate events. Although anti-desertification efforts have been mounted worldwide, most undertakings have shown poor performance because of failure to consider soil and geotechnical aspects. Soil erosion is accelerated by reductions in soil cohesion and water retention due to the transfer of fine particles from the original ground. Thus, soil internal cohesion must be recovered to ensure effective and reliable anti-desertification attempts. In this study, soil treatment using biopolymers is suggested as an alternative method to prevent soil erosion and for revitalization, taking into consideration engineering and environmental aspects. Even as a relatively small part of the soil mass (i.e., 0.5-1.0%), biopolymers in soil have the positive potential to significantly reduce the erodibility of soil by enhancing inter-particle cohesion. Moreover, biopolymer treatment also improves both vegetation germination and soil water retention characteristics against evaporation, and therefore can provide suitable environments for plants and crops used as a desertification countermeasure in arid and semi-arid regions where annual precipitation is limited. We suggest combining biopolymers with pre-existing anti-desertification efforts (e.g., afforestation and windbreaks) on desert fronts (i.e., boundaries between arid and semi-arid regions) for best efficiency. © 2015 Elsevier B.V.

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