e ground freezing technique was first invented for the undisturbed sampling of the granular soils. With increasing necessity of liquefaction evaluation under earthquake loading, there has been more research with high-quality granular samples, with ground freezing techniques in the world. However, there has been little research on the ground freezing techniques since Korea had no records of liquefactions until the Pohang earthquake in 2017. Since more than 10 places were reported with liquefaction phenomena, it is required to assess the liquefaction potential with high-quality samples of granular soils. erefore, in order to obtain undisturbed samples of granular soils, a new local ground freezing equipment and an operating system were developed in this study. e applied coolant was liquid nitrogen and circulated through a double tube inserted in the ground. To evaluate the performance of the system, laboratory scale tests were performed with water only and saturated fine sands. In the laboratory evaluation, a frozen soil column of 60 cm diameter was made after 20 hours and the average freezing rate was approximately 12 mm/hr in radial direction. After laboratory evaluation, the freezing system was applied in the field and the performance was evaluated with the 2D electrical resistivity tomography. In the field evaluation, the frozen region was 4 m diameter with 6.5 m depth in a cylindrical shape.

Recently, the participation on the development of the natural gas pipeline in Russia as well as the recent construction of the second Korean Antarctic research station, the Jangbogo station provide the research interests on the behavior of the permafrost ground. To investigate the effect of fines on the mechanical responses of frozen sands, unconfined compression tests were performed on the frozen sands with 0, 5, 10 and 15% of fine contents at -5, -10 and -15℃. The poorly graded (SP) Joomunjin sand and kaolinite, silt with low plasticity (ML) were used for the preparation of the frozen soil specimens. The mechanical responses of the tested soils were investigated via unconfined compression tests in the temperature controlled laboratory and analyzed in terms of peak unconfined compressive strength and secant modulus at 50% of the peak strength. As the fine contents increase, the unfrozen water contents increase and thus the strength and stiffness of frozen soils decrease. The increment of the stiffness and strength due to the temperature decrease vary with the fine contents.

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: There are many reclamation projects domestically and internationally which requires large quantity of reclaimable materials. To provide enough reclaimable soils which are limited in land, there have been various research focusing on the dredged soils in the marine environments. As a part of this research, a GIS based 3D dredging reclamation visualization program was developed for the volume estimation of dredged soils in 2015. The developed program is based on the digitized spatial information of the site investigation data with a consideration of the reliability of the data. Prior to the validation with the comparisons with the actual dredged volume measurement data, the developed program was compared with the commercial 3D visualization program with 3D visualized results from the test site near the Gunjang harbor. The validation of the developed program was performed in terms of the degree of visualized precision, the sectional and profiling of soil layers and the dredged volume estimation results. Based on the comparisons, both commercial and developed program show similar dredged volume with minor discrepancies in soil layers.

In this research, the three-point bending tests were conducted using frozen sand specimen of 0, 5, 10, and 15% fine contents with specified notch under −5, −10, and −15°C condition to analyse the effects of fine contents and temperature on the mode I fracture characteristics of the frozen sand. Three-point bending tests were performed using the standard test method of other materials such as metal and concrete. In order to investigate the effect of fine and temperature on the fracture characteristics of the frozen sand, the stress intensity factor and fracture energy were calculated using three-point bending test results. Based on the test results, fine contents and temperature can affect the brittle and ductile responses of the frozen sand. Furthermore, the fracture toughness of frozen sand increase with the fine contents’ increase and the temperature decrease. Fracture energy required for the crack initiation can be dominated by the fracture behaviour and brittle and ductile response.