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Shen B.,CSIRO | Guo H.,CSIRO | Ko T.Y.,SK Engineering and Construction | Lee S.S.C.,SK Engineering and Construction | And 8 more authors.
International Journal of Geomechanics | Year: 2013

This paper describes the theory behind a recent extension of a two-dimensional (2D) boundary-element code, FRACOD, to enable simulations of either coupled fracture (F)-hydraulic (H) processes or coupled F-thermal stress (T) in rocks. This extension is the next step in the ongoing development of a three-dimensional (3D) fracture mechanics code that couples F-H-T processes and predicts fracture initiation and propagation under thermal and hydraulic loadings. The original FRACOD simulated both mode I (tensile) and mode II (shear) fracture propagation that only involved mechanical processes in rock masses. In this study, the F-T coupling in FRACOD was developed using an indirect boundary-element method based on fictitious heat sources. The F-H coupling in FRACOD focused on fluid flow in explicit rock fractures using a cubic law. An explicit iteration method is used to simulate the fluid flow process in fractures and its interaction with mechanical deformation. Several verification and application cases have been included in the paper that demonstrate the effectiveness of the coupled functions. The extended code has been applied to the liquefied natural gas (LNG) underground storage experiment in South Korea and the Äspö pillar stability experiment (APSE) pillar spalling experiment in Sweden, and these applications are reported elsewhere. © 2013 American Society of Civil Engineers.

Chung S.-K.,Korea Institute of Geoscience and Mineral Resources | Park E.-S.,Korea Institute of Geoscience and Mineral Resources | Synn J.-H.,Korea Institute of Geoscience and Mineral Resources | Jeong W.-C.,SK Engineering and Construction | Kim T.-K.,SK Engineering and Construction
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

:A new technology for storing LNG in the underground cavern has been developed by combining the concept of groundwater drainage and an ice-ring with insulation system for LNG carriers and above-ground storage tank. Formation of the ice-ring, which is one of the core technologies forming LNG storage system, can be identified by a complex mechanism undergoing between the thermal characteristics of the rock mass and hydro-geological characteristics of groundwater. The key to the technology of LNG storage system have been well demonstrated through the design, construction and operation of the Pilot Plant existing at Daejeon, Korea. The results obtained from the study with regards to the formation of the ice-ring, showed that the freezing temperature of the water flowing through rock joints is affected by the latent heat during freezing, aperture of joints and the flow rate of groundwater. In the present study, the freezing temperature and the penetration length of groundwater was investigated by a thermo-hydraulic coupled analysis and CFD analysis of the groundwater flow in the joints during formation of the ice-ring. The factors affecting the freezing temperature of groundwater during the ice-ring formation are the rate of rise in groundwater level and the joint aperture. In addition, the numerical modeling studies demonstrated that the two factors were affecting each other prominently. The freezing temperature of groundwater in both narrow and wide aperture of a joint can be applied with a value higher than -3°C, which was assumed as freezing temperature in the past. However, these numerical analyses were conducted in a limited range with several assumed conditions. Therefore, further analysis with several other conditions would be necessary to clarify the freezing temperature of groundwater in the rock joints. © 2012 Taylor & Francis Group, London.

Shen B.,CSIRO | Shen B.,Shandong University of Science and Technology | Jung Y.-B.,Korean Institute of Geosciences and Mineral Resources | Park E.-S.,Korean Institute of Geosciences and Mineral Resources | Kim T.-K.,SK Engineering and Construction
Geosystem Engineering | Year: 2015

Underground storage of liquefied natural gas (LNG) has many advantages over the conventional above-ground LNG storage due to its safety and energy efficiency. One of the key technical challenges for the underground storage of LNG is to understand the behaviour of the rock mass in the vicinity of the LNG cavern and hence to take measures to prevent leakage caused by possible rock fracturing in response to the cooling of the rock mass. With the extremely low temperature of the LNG ( − 162°C) in the storage cavern, sub-zero temperatures will be induced in the surrounding rock mass, which on one hand may cause tensile stress due to thermo-mechanical effect and on the other will cause the formation of ice in pores and cracks of the saturated rock mass. Ice formation is likely to cause compressive stress in the rock mass due to its expansion in volume. The combined effect of rock cooling and ice swelling is complicated as cooling tends to create open fractures whereas ice swelling tends to cause compression and the closure of these discontinuities. Understanding this effect is crucially important as it is related to the integrity of the surrounding rock mass for leakage prevention. This study presents recent developments of the thermal-mechanical coupling and ice swelling functions in FRACOD, a numerical code designed to predict rock fracturing processes in fractured rock masses. The new functions enable us to investigate the complicated response of an in situ rock mass to the excavation of LNG cavern and the storage of low temperature LNG in a most realistic way. The pilot LNG storage cavern experiment at Daejeon Korea is used as a case study site, and the measured temperature in the surrounding rock mass are used to validate the numerical model and the modelling method. The ice swelling effect was modelled by introducing a large number of random cracks in the rock mass, which have certain hydraulic apertures to hold water. When the local rock temperature is below zero, the aperture water will become ice and cause crack expansion. It has been found in the study that ice swelling has a major effect on the displacement and stress distribution in the rock mass. It causes a compression zone around the LNG cavern, and effectively prevents tensile fracturing and fluid leakage. © 2015 The Korean Society of Mineral and Energy Resources Engineers (KSMER).

Khin K.,SK Engineering and Construction | Sakai T.,Kyushu University | Zaw K.,University of Tasmania
Gondwana Research | Year: 2014

The Arakan Basin is one of the major sedimentary basins formed in the frontal part of the Himalayan orogenic belt since the Late Cenozoic. Defining one of the four major sedimentary basins of Myanmar, it is geomorphologically and tectonically differentiated from the others. The study area along the westernmost edge of Myanmar is separated from the Arakan Yoma (Indo-Burman Ranges) by a narrow coastal strip and is bordered by the Bay of Bengal to the west.Regional stratigraphic correlation and the geological age of the siliciclastic sequences were established based on planktonic foraminiferal zonation. Deep marine slope and shelf environments during Early- to Middle Miocene (ca. 21.5-11. Ma), and a southward prograded shelf-delta environment during Late Miocene to Pliocene time were determined.The Early Miocene underthrusting along the Himalayan front is well documented by the forced-regressive sedimentation patterns in the slope and shelf systems, sediments of which derived from the paleo-Ganges-Brahmaputra river systems in the Bengal-Arakan basins. Sequential evolution of the Miocene successions manifests in forced regressive wedged systems tracts. These evolved through slope by-passing and slumping and, following deep-marine channel in-filling, began to accumulate an increasing sediment load due to the rapid fall of sea level by the uplift in the hinterlands during the Early- to early-Middle-Miocene.The formation of a shelf-delta systems marks a dramatic shift in the evolution of the southward prograding delta systems following a eustatic sea-level low. In the foreland areas, erosional off-loading with foreland uplifting caused a wide active fluvial systems and formed transverse rivers distally in the late-Middle- to Late-Miocene. © 2013 International Association for Gondwana Research.

Yun T.S.,Yonsei University | Lee J.-S.,Korea University | Lee S.-C.,SK Engineering and Construction | Kim Y.J.,Yonsei University | Yoon H.-K.,Korea University
KSCE Journal of Civil Engineering | Year: 2011

The renewable energy has been investigated as an alternative resource to resolve the demanding consumption of conventional hydrocarbon energy, to minimize the environmental impact, and to secure the sustainability for decades. The exploitation of renewables is often hampered due to the intermittence, site-dependency, and the lack of engineering experiences. The objective of this paper is to introduce the characteristics of various renewable energies and to examine the roles for geotechnical engineers. Beginning with the synopsis of worldwide energy consumption, an overview is presented for renewable energy sources of air, water, heat and organics in terms of associated technologies and issues related to geotechnology. The compressed air energy storage system related to geomaterials is introduced, and the challenges that may need to be advanced by geotechnology are proposed. This paper shows that Optimized site characterization, advanced geotechnical tools, and real-time monitoring systems are necessary for the geotechnical construction of renewable energy systems. © 2011 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.

Kim E.Y.,Inha University | Kim M.S.,SK Engineering and Construction | Lee S.K.,Inha University
Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference 2009, DETC2009 | Year: 2010

A time frequency technique for locating leaks in buried gas distribution pipes involves the use of the cross-correlation on two measured acoustic signals on either side of a leak. This technique can be problematic for locating leaks in steel pipes, as the acoustic signals in these pipes are generally narrowband and low frequency. The effectiveness of the time-frequency technique for detecting leaks in steel pipes was investigated experimentally in an earlier study. The object of this paper is to identify the characteristics of this dispersive acoustic wave through analysis of the cut-off frequency by using the time-frequency method experimentally and BEM (boundary element method) theoretically for the development of an experimental tool to analyze the leak signals in steel pipe. The tool is based on experimental work and theoretical formulation of wave propagation in a fluid-filled pipe. This tool uses the time-frequency method to explain some of the features of wave propagation measurements made in gas pipes. Leak noise signals are generally passed through a time-frequency filter for detection of impulse signal related leakage. Copyright © 2009 by ASME.

Lee T.-H.,Korea Infrastructure Safety and Technology Corporation | Chul I.J.,Pusan National University | Kim C.,SK Engineering and Construction
Marine Georesources and Geotechnology | Year: 2015

The in-situ application of micropiles has gradually increased in limited spaces of downtown areas because the micropile has various advantages, such as low vibration and noise and compact machine size. In this study, model tests were carried out to understand the reinforcement effect induced by the mechanical interaction between the micropile and soil. The micropiles were installed in the soil adjacent to footings. Factors such as reinforced range (W) with piles, spacing (S) between piles, the installed angle (θ) of piles, and pile length (L) were considered variables in the tests. The reinforced angle (θ) was a more critical factor than the others for restraining the settlement and increasing soil stiffness in the model test results. The reinforcement effect rapidly increased around the reinforced range (W) of 2B (B: the width of a footing), the reinforced angle (θ) of 45 ∼ 75°, and the pile length (L) of 3B. Based on the results of the experimental analyses, the purpose of this study is to improve the reinforcement efficiency of micropiles by recommending the most effective pattern and design method for installing them. 2015 Copyright © Taylor & Francis Group, LLC

Ko T.Y.,SK Engineering and Construction | Kemeny J.,University of Arizona
International Journal of Rock Mechanics and Mining Sciences | Year: 2013

Subcritical crack growth plays an important role in evaluating the long-term stability of structures in rocks. The characteristics of subcritical crack growth can be described by a relationship between the stress intensity factor and the crack velocity. This paper presents the results of studies conducted to validate the constant stress-rate test for determining subcritical crack growth parameters in rocks, compared with the conventional testing method, the double torsion test. Various types of specimens including the Brazilian disk, three-point bending, grooved disk, single edge notched bend, and compact tension specimens have been tested on Coconino sandstone under the constant stress-rate scheme and the subcritical crack growth parameters have been determined. The results of the constant stress-rate test are in good agreement with the results of double torsion test. More importantly, the stress-rate tests can determine the parameter A with a much smaller standard deviation than the DT test. Thus the constant stress-rate test seems to be a valid test method for rocks. The results show that the parameter n is almost constant regardless of the test method and specimen geometry, but the parameter A varies with the test method and specimen geometry. © 2012 Elsevier Ltd.

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