• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.1
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• pp.43-50
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• 2005

This test was performed to evaluate the change of the unconfined compressive strength, strength parame¡?ters which resulted from direct shear test and oil residue percents analyzed by GC-MS as time lapse, oil addition. Unconfined compression strength of $10\%$ kerosene added by weight of dry soil recovered as time passed. In the case of $5\%$ kerosene added, the strength recovered as much as clean clayey soil after about 50 days passing. For the case of diesel added, the recovery of unconfined compressive strength was not shown even though about 60 days passed. The strength parameters (c, $\psi$) of kerosene added not changed but for diesel added, the cohesion was very decreased as diesel addition increased. Residual percent of kerosene in the soil was less than that of diesel as time passed.

• Geomechanics and Engineering
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• v.25 no.2
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• pp.89-98
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• 2021

The paper presents an experimental study on the strength behaviour of a coral gravelly sand from Vietnam subjected to monotonic and cyclic loading. A series of direct shear tests were carried out to investigate the shear strength behaviour and the factors affecting the shear strength of the sand such as relative density, cyclic load, amplitude of the cyclic load and loading rate. The study results indicate that the shear strength parameters of the coral gravelly sand include not only internal friction angle but also apparent cohesion. These parameters vary with the relative density, cyclic load, the amplitude of the cyclic load and loading rate. The shear strength increases with the increase of the relative density. The shear strength increases after subjecting to cyclic loading. The amplitude of the cyclic load affects the shear strength of coral gravelly sand, the shear strength increases as the amplitude of the cyclic load increases. The loading rate has insignificantly effect on the shear strength of the coral gravelly sand.

• Structural Engineering and Mechanics
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• v.83 no.3
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• pp.377-386
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• 2022

This paper considers dynamic impedance functions and presents a detailed analysis of the soil plasticity influence on the pile-group foundation dynamic response. A three-dimensional finite element model is proposed, and a calculation method considering the time domain is detailed for the nonlinear dynamic impedance functions. The soil mass is modeled as continuum elastoplastic solid using the Mohr-Coulomb shear failure criterion. The piles are modeled as continuum solids and the slab as a structural plate-type element. Quiet boundaries are implemented to avoid wave reflection on the boundaries. The model and method of analysis are validated by comparison with those published on literature. Numerical results are presented in terms of horizontal and vertical nonlinear dynamic impedances as a function of the shear soil parameters (cohesion and internal friction angle), pile spacing ratio and frequencies of the dynamic signal.

• Geomechanics and Engineering
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• v.36 no.4
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• pp.391-406
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• 2024

In order to study the soil seasonal dynamic characteristics in the regions with four distinct seasons, the soil dynamic triaxial experiments were conducted by considering the environmental temperature range from -30℃ to 30℃. The results demonstrate that the dynamic soil properties in four seasons can change greatly. Firstly, the dynamic triaxial experiments were performed to obtain the dynamic stress-strain curve, elastic modulus, and damping ratio of soil, under different confining pressures and temperatures. Then, the experiments also obtain the dynamic cohesion and internal friction angle of the clay under the initial strain, and the changing rule was summarized. Finally, the results show that the dynamic elastic modulus and dynamic cohesion will increase significantly when the clay is frozen; as the temperature continues to decrease, this increasing trend will gradually slow down, and the dynamic damping ratio will go down when the freezing temperature decreases. In this paper, the change mechanism is objectively analyzed, which verifies the reliability of the conclusions obtained from the experiment.

• Journal of computational fluids engineering
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• v.19 no.4
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• pp.14-19
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• 2014

This study conducts shape optimization of rib turbulator on the internal cooling passage that has triangular cross-section of high pressure turbine nozzle. During optimization, various types of rib turbulator including angled, V-shaped, A-shaped and angled rib with intersecting rib are considered. Each type of rib turbulator is parameterized with attack angle(s), rib height, spacing ratio and bending/intersecting location. For optimization, Design of Experiment (DOE) and Kriging surrogate model are used to utilize computational resource more efficiently and Genetic Algorithm (GA) is used to search the optimum points. As a result, Pareto front of each type of rib turbulator with friction factor that relates to pressure drop in cooling passage and spatially averaged Nusselt number that relates to heat transfer on the wall is drawn and optimum points on the Pareto front are suggested.

• The Journal of Engineering Geology
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• v.18 no.3
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• pp.277-285
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• 2008

For the soil nailing, recently, its application is expanded, but there is no officially approved method to design it yet. Furthermore, there are a great number of design valuables in soil nailing, it is also used without clear data under the situation that uncompleted detailed research on the sensibility between design variables. Especially, there has no deal with the installation angle of the nail - the major contents in this study. Therefore, this study based on the theoretical estimation analyzed safety rate about the angle of the nail, unit weight, adhesive force, internal friction angle and tensile farce worked on nail in the case of the rear of pond side is both horizontal and perpendicular. As a result, it could be verified that the safety rate increased on every cases in the situation of the nail installation angle was in upward direction than in downward direction.

• Korean Journal of Agricultural Science
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• v.5 no.1
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• pp.15-28
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• 1978

It has been known that the shear strength of soil is an important design parameter for the foundation of structures, the retaining walls, the slope failures and so forth. In this study, the shear test was performed by using the direct shear apparatus under various degree of the moisture content and the density of the sample soils. The results of the study were summarized as follows; 1. The shear strength of soil increased with increase in the dry density of soil, and at the same level of density of the sample the shear strength of soil showed large values on a good grading of the sample. 2. The cohesion of the soil varied directly with the dry density of it, however the internal friction angle of soil was not affected by the dry density of tile sample. 3. The shear strength of sample varied inversly with the moisture content of it, and this phenomenon was apparent on a good grad ing of sample. 4. The cohesion of soil showed maximum value when the moisture content of the soil reached optimum level and the internal friction angle decreased with increase in the moisture content of it. These phenomena were very obvious on a good grading sample, SDC-1. 5. The cohesion of the soil decreased with increase in void ratio of the sample, but the internal friction angle of the sample didn't show such tendency.

• Geotechnical Engineering
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• v.7 no.3
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• pp.21-32
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• 1991

The purpose of this paper is to develop a reliability model for slope stability of Earth-rockfill dams which accounts for all uncertainties encountered. The uncertain factors of the design variables include the cohesion, the angle of internal friction, and the porewater Pressure in each zone. More specifically, the model errors in estimating those variables are studied in depth. To reduce the uncertainties due to model errors, updated design variables are obtained using Bayesian Theory. For stability analysis, both the two-dimesional stability analysis and the three-dimensional stability analysis where the end effects and the system reliability concept are considered are used for the reliability calculations. The deterministic safety factor by the three-dimensional analysis is lager than that by the two-dimensional anlysis. However, the probability of failure by the three-dimensional analysis is about 3.5 times larger that by the two-dimensional analysis. It is because the system reliability concept is used in the three-dimensional analysis. The sensitivity analysis shows that the probability of failure is more sensitive to the uncertainty of the cohesion than that of the angle of internal friction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.195-205
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• 2013

This study, using the MCC Model to consider consolidation, estimated the range within which no influences occur from lateral movement and its amount of the foundation pile and abutment on the soft ground. This study performed finite element analyses, with variations on the adhesiveness and internal friction angle, depth of soft clay, embankment height, consolidation parameters, and separation distance between the abutment and embankment. The abutment's horizontal displacement exhibits linear change with a longer separation distance, and changes into an exponential form as the embankment gets closer to the abutment. As the soft clay layer becomes 10 m deeper, the horizontal displacement tends to increase 1.5~3.0 times. However, it decreases at a rate of 0.3~0.95 when adhesiveness is increased by 10 $kN/m^2$ and internal friction angle is increased by $5^{\circ}$. The increase change rate in a lateral movement amount becomes greater if it is closer to the abutment when the abutment separation distance is long. When the distance is short, the change rate of horizontal displacement increases in similar a way, but it tends to be decreasing overall.

• Journal of the Korean Geotechnical Society
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• v.30 no.2
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• pp.65-76
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• 2014

For soil improvement, sand mats or sand compaction piles are often constructed on soft marine clays. In such cases, some amounts of sand and clay are inevitably mixed. Sand or gravel often exists in the weathered soils near the slope surface. This research investigates the effect of mixing sand content on consistency limits and shear strength of clays. Firstly, sand was mixed with kaolinite or bentonite at 0, 9, 17, 23, 29, 33, 50% and then liquid and plastic limits were measured. Both plastic and liquid limits decreased as a sand content increased. The water content of clay-sand mixtures with different sand content increased by 10% or 20% step by step and then their undrained shear strength was measured using a portable vane shear device called Torvane. For all cases, undrained shear strength of clay-sand mixtures decreased rapidly until reaching a certain value. Their state changed from undrained to drained state gradually as the sand content increased, which caused their undrained shear strength to decrease. On the other hand, a series of direct shear tests were also conducted on such clay-sand mixtures to investigate the effect of sand content on cohesion and angle of internal friction. It was found from clay-sand mixtures that their cohesion decreased but angle of internal friction increased as the sand content increased.