• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.239-246
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• 2000

It has been generally much fine contents in West Coast of Korea. When cyclic shear stress causing liquefaction was estimated as using cyclic triaxial tests in these grounds, it didn't appear linear relations between deviator stress and confining stress where σ'₃ was more than 150 kpa. Namely, due to no normalization of cyclic shear stress ratio, the errors of this is increased. Therefore, more confining stress is increased, more increment of deviator stress is decreased. So, using linear relations between tanø'/sub d/ of dynamic internal friction angle and CSR where σ'₃ was less than 150 kpa, liquefaction of these grounds was evaluated. Also, as doing detail evaluation which had carried response analysis of earthquake, this appeared good results which was well compatible with empirical methods using N-value of SPT. It was thought that these result evaluated vulnerable liquefaction area more correct than existing methods. Also, characteristics of liquefaction in West Coast grounds was compared with clean sands, with analysis of behavior of pore pressure ratio and axial strain affected by fine contents, as cyclic loading was applied.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.179-184
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• 2005

Shear strength parameters obtained from filed survey are important factors in the analysis of slope stability. In this study, sensitivity analysis was performed to evaluate the effect of input parameters on the analysis of slope stability. The input parameters selected for sensitivity analysis were slope angle, cohesion, and friction angle. Monte-Carlo Simulation method was used for calculating input parameters and the factor of safety was computed by means of limit equilibrium method. A rock slope, which has failed in the field, was used for the sensitivity analysis in the analysis of slope stability. The result of analysis shows that the factor of safety of the rock slope was a little low. From partial correlation coefficient(PPC) of input parameters determined from the sensitivity analysis, slope stability was dependant on cohesion and slope angle. The effect of friction angle was lower than that of cohesion and slope angle on slope stability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.5 s.236
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• pp.545-553
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• 2005

In the present study, The characteristics of developing steady laminar flows of a straight duct connected to a $180^{\circ}$ curved duct were examined In the entrance region through experimental measurement. Flow characteristics such as shear stress distributions, pressure distributions and friction coefficient experimentally in a square cross-sectional straight duct by using the PIV system. For the PIV measurement by particles produced from mosquito coils particles. The experimental data were obtained at 9 points dividing the test sections by 400mm. Experimental results can be summarized as follows. Critical Reynolds number, $Re_{cr}$ which indicates transition from laminar steady flow to transition steady flow was 2,150. Shear stress per unit length on the wall was stronger than that in the fully developed flow region. This was attributed to the fact that shear stress and pressure loss in the curvature of a duct were increased. Pressure distributions were gradually decreased irrespective of Reynolds number In the whole test section. This trends were in a good agreement with the reference results. Pipe friction coefficient in the steady state flow region was calculate from method of least squares. The co-relationship between fiction coefficient and Reynolds number was established as follow; ${\lambda}=56/Re$.

• Geomechanics and Engineering
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• v.20 no.6
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• pp.497-503
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• 2020

In the Kingdom of Saudi Arabia, the shallower depth of the earth's crust is composed of loose dune or beach sand with soluble salts. The expansive behavior of salt bearing soil, fluctuation of ground water table and extreme environmental conditions offer a variety of geotechnical problems affecting safety and serviceability of the infrastructure built on it. Despite spending money, time and other resources on repair and rehabilitation, no significant attention is paid to explore the root causes of excessive differential settlement and cracking to these facilities. The scientific solution required to ensure safety and serviceability of the constructed infrastructure is to improve the strength and durability properties of the supporting ground. In this study, shredded plastic is employed as a low cost and locally available additive to improve strength characteristics of the desert sand. The study shows a remarkable increase in the shear strength and normal settlement of the soil. A seven (07) degree increase in angle of internal friction is achieved by adding 0.4 percent of the shredded plastic additive. The effect of different proportions and sizes of the plastic strips is also investigated to obtain optimum values. Such a long-lived solution will seek to reduce maintenance and repair costs of the infrastructure facilities laid on problematic soil along with reduction of environmental pollutants.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09b
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• pp.53-60
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• 2010

The natural soils are classified in saturated soils and unsaturated soils according to level of ground water but the research for only saturated soils has been conducted by this time. However, there are many proble.ms which are not solved by using the concept and principle of saturated soils on the natural soils. In fact, it is known that unsaturated soils represent the behavior characteristic unlike completely saturated soils because of the adhesion under the influence of negative pore water pressure, the high angle of friction and the low water permeability by the air entry. So it needs to conduct the various researches on insufficient unsaturated soils. In this paper, unsaturated triaxial compressive tests are conducted in order to do research on shear strength characteristic on sands and silty sands of Nakdong river. As a result of the tests, the cohesion is increased in non-linear type according to the change of the matric suction, but the angle of internal friction is not changed much.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.131-140
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• 2015

This paper presents overall procedure by experimental study in order to deriving design factors of snow removal machine on roof of multi-span greenhouse. For the purpose of the testing, the scale model of the machine was made in the form to drive above the monorail. The test was performed in order to calculating friction coefficient of the machine and shear coefficient between sliced horizontal section of snow at constant temperature and humidity room in National Academic of Agricultural Science. As a result of the laboratory test, shear coefficient between sliced horizontal section of snow were calculated 1.60~2.37. Further investigation, we will study to derive the relationship between the real and scaled model through the field test.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.69-75
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• 2014

The shear strength characteristics of an unsaturated earth material are highly important not only for evaluating the seepage characteristics but also the stability of levee for a lifelong. In this study, unsaturated strength characteristics of Nak-dong river sand and clay that frequently used for the levee construction in southern province of Korea were analyzed using unsaturated triaxial compressive test. The strength characteristics due to the variation of matric suction were analyzed using multi-stage compression technique and the results were directly compared with the non-linear formulation for the apparent cohesion ($C_{max}$), and the friction component ${\varphi}^b$ were determined and evaluated from the test for the application of linear Mohr-Coulomb failure criteria. Cohesion and friction characteristics of the unsaturated levee material under various suction phases were also explored during this study.

• Tribology and Lubricants
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• v.23 no.3
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• pp.95-102
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• 2007

In recently designed diesel engines, the running conditions for piston pin bearings have become very severe due to combustion pressure and temperature increase. Moreover, the lead removal from the bush material has strongly reduced the capability of the anti friction material to accept asperity contacts. In this paper, before trying to find the pressure distributions on the oil film of piston pin bearings by the unsteady two dimensional thermohydrodynamic lubrication analysis in order to do the optimum design of the bearings of piston pin, it will be investigated the tendancy of piston pin rotating motion by calculating the friction coefficient at piston pin bearings, the oil film thickness and the frictional torques induced by hydrodynamic shear stress.

• Geomechanics and Engineering
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• v.3 no.4
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• pp.285-290
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• 2011

This article employs Multivariate Adaptive Regression Spline (MARS) for determination of friction capacity of driven piles in clay. MARS is non-parametric adaptive regression procedure. Pile length, pile diameter, effective vertical stress, and undrained shear strength are considered as input of MARS and the output of MARS is friction capacity. The developed MARS gives an equation for determination of $f_s$ of driven piles in clay. The results of the developed MARS have been compared with the Artificial Neural Network. This study shows that the developed MARS is a robust model for prediction of $f_s$ of driven piles in clay.

• Structural Engineering and Mechanics
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• v.21 no.1
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• pp.1-18
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• 2005

Foschi's connector model is used as a basic component in the development of nonlinear analysis programs for timber structures. This paper presents the extension of the model to include the effect of shaft frictional forces. The wood medium is modeled using the Foschi embedment model, while shaft friction is modeled using an elastic Coulomb-type friction model. The initial confining pressure for the case of driven fasteners is accounted for by a lateral shift of the load-embedment curve. The model is used to compute the cyclic response of both driven and inserted fasteners. The results obtained from the cases studied indicate that initial confining pressure and friction do not have a significant effect on the computed hysteretic response, however, they significantly affect the computed amount of fastener withdrawal. This model is particularly well-suited for modeling the hysteretic response of shear walls with moderate fastener withdrawal under lateral cyclic or earthquake loading.