• Geomechanics and Engineering
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• v.11 no.5
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• pp.713-723
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• 2016

Shear wave velocities of three selected sandy soils subject to drained triaxial compression test were continuously measured using the bender elements. The shear wave velocity during isotropic compression, as widely recognized, increased as confining pressure increased and they were correlated well. However, during drained shearing, the mean effective stress could no further provide a suitable correlation. The shear wave velocity during this stage was almost constant with respect to the mean effective stress. The vertical stress was found to be more favorable at this stage (since confining stress was kept constant). When sample was attained its peak stress, the shear wave velocity reduced and deviated from the previously existed trend line. This was probably caused by the non-uniformity induced by the formation of shear band. Subsequently, void ratios computed based on external measurements could not provide reasonable fitting to the initial stage of post-peak shear wave velocity. At very large strain levels after shear band formation, the digital images revealed that sample may internally re-arrange itself to be in a more uniform loose stage. This final stage void ratio estimated based on the proposed correlation derived during pre-peak state was close to the value of the maximum void ratio.

• Geotechnical Engineering
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• v.9 no.4
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• pp.27-36
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• 1993

The drained and undrained behavior of pure silt was investigated experimentally. Special attention was given to the stress-strain behavior of silt prior to failure and behavior at failure under monotonic and cyclic loading. A pure silica flour was chosen to form samples with two different densities of D,=80%, eo=0.68 and D,=35%, eo=0.9. The isotropically consolidated samples were tested in the triaxial testing device under monotonic undrained, drained compression and extension conditions. Also samples were tested under cyclic undrained condition. Based on the experimental results. it was qualitively identified that the overall behavior of silt is similar to that of sand. When compared with clay, silt shows a significantly different behavior due to its dilatant nature under both the monotonic and cyclic shear loadings.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.2
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• pp.155-162
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• 2016

A proton exchange membrane fuel cell (PEMFC) produces only water at cathode by an electrochemical reaction between hydrogen and oxygen. The generated water is transported across the membrane from the cathode to the anode. The transported water collected in water-trap and drained to the cathode within the humidifier outlet. If the condensate water is not being drained at the appropriate time, condensate water in the anode can cause the performance degradation or fuel efficiency degradation of fuel cell by the anode flooding or unnecessary hydrogen discharge. In this study, we proposed an optimization method of condensate water drain logic for the water drain performance and the water drain algorithm as considered the condensate water generating speed prep emergency case. In conclusion, we developed the water management strategy of fuel processing system (FPS) as securing fuel efficiency and operating stability.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.3
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• pp.74-83
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• 1994

A series of isotropic consolidation tests, undrained and drained triaxial compression tests was carried out to investigate the physical characteristics and behaviours of marine silty sands collected from the western coast of Korea. This study also included a theoretical development of the constitutive equation to evaluate stress-strain relationship and volume change of silty sands. The results and main conclusions of the study are summarized as follows; 1. Isotropic compression and swelling index are linearly decreased with an increase in relative density. 2. Both undrained shear strengh and elastic modulus are increased with an increase in relative density and confining pressure. 3. Internal friction angles obtained from drained and undrained compression tests of the soils are proportional to relative density. 4. The phenomenon of dilatancy of each sample is less profound when confining stress is increased but more profound when relative density is increased. 5. The slope of critical state lines is 1.78 for Saemangum, 1.70 for Siewha and 1.26 for Sukmoon sands. 6. In this study, Drucker-Praper type criterion is used and hardening function of Cap model is modified by hyperbolic fuction. This will improve a lack of physical meaning of hardening parameters in conventional Cap model. 7. A newly developed constitutive equation to the forementioned silty sands and checked its applicability. This is in good agreement with the measured data.

• Geomechanics and Engineering
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• v.9 no.6
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• pp.729-742
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• 2015

The aim of the present work was the study of instability in a loose sand from Les Dunes beach in Ain Beninan, Algeria, where the Boumerdes earthquake occurred in 2003. This earthquake caused significant structural damages and claimed the lives of many people. Damages caused to infrastructures were strongly related to phenomena of liquefaction. The study was based on the results of two drained and six undrained triaxial tests over a local sand collected in a region where liquefaction occurred. All the tests hereby analyzed followed compression stress-paths in monotonic conditions and the specimens were isotropically consolidated, since the objective was to study the instability due to static loading as part of a more general project, which also included cyclic studies. The instability was modeled with the second-order work increment criterion. The definition of the instability line for Les Dunes sand and its relation with yield surfaces allowed the identification of the region of potential instability and helped in the evaluation of the susceptibility of soils to liquefy under undrained conditions and its modeling. The dilatancy rate was studied in the points where instability began. Some mixed tests were also simulated, starting with drained conditions and then changing to undrained conditions at different time steps.

• Geomechanics and Engineering
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• v.23 no.6
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• pp.561-573
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• 2020

The creep and consolidation behaviors of clays subjected to thermal cycles are of fundamental importance in the application of energy geostructures. This study aims to numerically investigate the physical mechanisms for the temperature-triggered volume change of saturated clays. A recently developed thermodynamic framework is used to derive the thermo-mechanical constitutive model for clays. Based on the model, a fully coupled thermo-hydro-mechanical (THM) finite element (FE) code is developed. Comparison with experimental observations shows that the proposed FE code can well reproduce the irreversible thermal contraction of normally consolidated and lightly overconsolidated clays, as well as the thermal expansion of heavily overconsolidated clays under drained heating. Simulations reveal that excess pore pressure may accumulate in clay samples under triaxial drained conditions due to low permeability and high heating rate, resulting in thermally induced primary consolidation. Results show that four major mechanisms contribute to the thermal volume change of clays: (i) the principle of thermal expansion, (ii) the decrease of effective stress due to the accumulation of excess pore pressure, (iii) the thermal creep, and (iv) the thermally induced primary consolidation. The former two mechanisms mainly contribute to the thermal expansion of heavily overconsolidated clays, whereas the latter two contribute to the noticeable thermal contraction of normally consolidated and lightly overconsolidated clays. Consideration of the four physical mechanisms is important for the settlement prediction of energy geostructures, especially in soft soils.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.41-51
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• 2023

Cementitious materials such as Ordinary Portland Cement (OPC), fly ash, lime, and bitumen have been employed for soil improvement over the years. However, due to the environmental concerns associated with the use of OPC, substituting OPC with calcium sulfoaluminate (CSA) cement offers good potential for ground improvement because it is more eco-friendly. Although earlier research has investigated the stabilizing effects of CSA cement-treated sand, no attempt has been made to examine soil behavior under high confining pressure. As a result, this study aimed to investigate the shear strength and mechanical behavior of CSA cement-treated sand using a consolidated drained (CD) triaxial test with high confining pressure. The microstructure of the examined sand samples was investigated using scanning electron microscopy. This study used sand with CSA cement contents of 3%, 5%, and 7% and confining pressures of 0.5, 1.0, and 1.5 MPa. It revealed that the confining pressures and CSA cement content significantly affected the stress-strain and volumetric change behavior of CSA cement-treated sand at high confining pressures.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.197-208
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• 2023

Rate-dependent mechanical response of sand, subjected to loading of medium to high strain rate range, is of interest for several civilian and military applications. Such rate-dependent response can vary significantly based on the initial density state of the sand, applied confining pressure, considered strain rate range, drainage condition and sand morphology. A numerical study has been carried out employing a recently proposed visco-plastic constitutive model to explore the rate-dependent mechanical behaviour of Toyoura sand under drained triaxial loading condition. The model parameters have been calibrated using the experimental data on Toyoura sand available in published literature. Under strain rates higher than a reference strain rate, the simulation results are found to be in good agreement with the experimentally observed characteristic shearing behaviour of sand, which includes increased shear strength, pronounced post-peak softening and suppressed compression. The rate-dependent response, subjected to intermediate strain rate range, has further been assessed in terms of enhancement of peak shear strength and peak friction angle over varying initial density and confining pressure. The simulation results indicate that the rate-induced strength increase is highest for the dense state and such strength enhancements remain nearly independent of the applied confinement level.

• Korean Journal of Radiology
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• v.2 no.3
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• pp.164-170
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• 2001

Objective: To evaluate the technical feasibility and the clinical effectiveness of sclerotherapy for the treatment of peritoneal inclusion cysts (PICs). Materials and Methods: Between June 1996 and February 2001, eight PICs in seven female patients aged 28-43 (mean, 36) years were instilled with sclerosant (povidone-iodine in three, ethanol in three, both povidone-iodine and ethanol in one). All seven patients subsequently experienced less abdominal pain. After drainage via an 8.5-Fr pigtail catheter inserted in the PICs (transabdominally in six cases, transvaginally in one), sclerosant equivalent in volume to about one-third that of drained fluid was introduced daily until the drained volume was less than 5ml. Follow-up by means of clinical procedures and ultrasound was performed every three months, at which time the success rate, possible complications and recurrence were determined. Results: Sclerotherapy was technically successful in all seven patients, though immediately after the procedure, minor complications were noted in three patients (mild pain in two, mild fever in one). During the follow-up of 4-60 (mean, 24.7) months, sclerotherapy proved successful and without long-term complications in all seven patients: lower abdominal pain disappeared and the diameter of the cysts decreased more than 50%, with complete regression in four cases. During the follow-up period there was no recurrence. Conclusion: Sclerotherapy following catheter insertion is technically feasible and effective for the treatment of PICs.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.2
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• pp.97-103
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• 2004

This study was performed to assess the influences of liquid pig manure (LPM) on the rice growth and nutrient behavior in soil under two different drainage comditions. Soils of paddy field were Jeonbuk and Gangseo series, and drainage conditions of the soils were imperfectly drained and moderate well drained, respectively, Application of LPM was based on nitrogen, and the treatments included 110 (LPM-N100%), 165 (LPM-N150%) and $220(LPM-N200%)kg\;N\;ha^{-1}$. In the LPM-N150% treatment, rice growth and yield were similar to the control treatment of conventional chemical fertilizer application. Rice yield of moderately well drainedfield were 3-11% higher than that of imperfectly drained field. Loss of nitrogen through $NH_3$ gas after application of LPM was higher in no plowing than in rotary plowing field. Losses of $NO_3-N$, $NH_4-N$, $SO_4$, Ca and K through runoff water were increased as the amount of LPM application increased. Losses of $NO_3-N$ and K through infiltration were higher in LPM-150% and LPM-N200% treatments compared to the chemical fertilizer treatment. Contents of $NO_3-N$ in infiltration water measured from trasplanting to tillering stage was higher at the moderately well drained condition than imperfectly drained condition. Contents of $P_2O_5$ and K in soil were accumulated by application of LPM compared to the chemical fertilizer plot.