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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Geotechnical Society
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Journal DOI :
Korean Geotechical Society
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Volume & Issues
Volume 24, Issue 12 - Dec 2008
Volume 24, Issue 11 - Nov 2008
Volume 24, Issue 10 - Oct 2008
Volume 24, Issue 9 - Sep 2008
Volume 24, Issue 8 - Aug 2008
Volume 24, Issue 7 - Jul 2008
Volume 24, Issue 6 - Jun 2008
Volume 24, Issue 5 - May 2008
Volume 24, Issue 4 - Apr 2008
Volume 24, Issue 3 - Mar 2008
Volume 24, Issue 2 - Feb 2008
Volume 24, Issue 1 - Jan 2008
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A Case Study on the Hybrid Reinforcement Retaining Wall System Reinforced by Soil Nail and Steel Strip
Chun, Byung-Sik ; Kim, Hong-Taek ; Cho, Hyun-Soo ; Do, Jong-Nam ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 5~12
The reinforced earth wall, which is able to improve the strength of soil highly, is required in case of supporting high surcharge load such as high speed rail way, high embankment road, and massive reinforced earth wall in a mountainous area. And also, it is continuously required that the method is able to minimize the amount of excavated soil on account of environmental issue, boundary of land, etc., on excavation site. However, because the required length of reinforcement should be
of the height of reinforced earth wall for general reinforced earth wall, in fact the reinforced earth wall is hardly applied on the site of cut slope. In this paper we studied the design and construction cases of hybrid reinforcement retaining wall system combined with steel strips and soil nails, connecting the reinforced earth wall reinforcements to the slope stability reinforcements (soil nails) to ensure sufficient resistance by means of reducing the length of reinforcements of reinforced earth wall. And the feasibility of hybrid reinforcement retaining wall system, suggested by real data measured on site, is also discussed.
Calculation of Bearing Capacity of Tapered Drilled Shafts in Cohesionless Soils Using Shape Factor
Paik, Kyu-Ho ; Lee, Jun-Hwan ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 13~22
Fourteen calibration ehamber tests were performed using one cylindrical and two tapered piles with different taper angles to investigate the changes of the bearing capacity of tapered piles with soil state and taper angle of piles. The results of calibration chamber tests show that the ultimate base resistance of tapered piles increases with increasing mean stress and relative density of soil. It also increases with increasing taper angle for medium sand, but with decreasing taper angle for dense sand. The ultimate shaft resistance of tapered piles increases as vertical and horizontal stresses, relative density and taper angle increase. Based on the results of model pile load tests, a new design method with shape factors for estimation of the bearing capacity of tapered piles is proposed considering the effect of soil state and taper angle on bearing capacity of tapered piles. In order to check the accuracy of predictions calculated using the new method, middle-scale field pile load tests were also conducted on cylindrical and tapered drilled shafts in clayey sand. Comparison of calculated values with measured ones shows that the new design method produces satisfactory predictions tor tapered piles.
Numerical Investigation on the Stability of Reinforced Earth Wall during Rainfall
Yoo, Chung-Sik ; Kim, Sun-Bin ; Han, Joon-Yeon ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 23~32
This paper presents the results of numerical investigation on the stability of reinforced earth wall during rainfall. A series of limit-equilibrium based slope stability analyses within the framework of unsaturated shear strength, coupled with transient seepage analyses, were conducted with due consideration of rainfall characteristics in Korea. It is shown that the factor of safety of the reinforced wall during rainfall decreases with time due to decreases in the suction in the reinforced as well as retained zones. Also revealed is that the decrease in the factor of safety depends not only on the backfill soil type but also on the rainfall characteristics. Practical implications of the findings were discussed.
FE Analysis of Rock-Socketed Drilled Shafts Using Load Transfer Method
Seol, Hoon-Il ; Jeong, Sang-Seom ; Kim, Young-Ho ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 33~40
The load distribution and deformation of rock-socketed drilled shafts subjected to axial loads are evaluated by a load-transfer method. The emphasis is on quantifying the effect of coupled soil resistance in rock-socketed drilled shafts using the 2D elasto-plastic finite element analysis. Slippage and shear load transfer behavior at the pile-soil interface are investigated by using a user-subroutine interface model (FRlC). It is shown that the coupled soil resistance provides the influence of pile toe settlement as the shaft resistance is increased to an ultimate limit state. The results show that the coupling effect is closely related to the value of pile diameter over rock mass modulus (D/
) and the ratio of total shaft resistance against total applied load (
/Q). Through comparisons with field case studies, the 2D numerical analysis reseanably presented load transfer of pile and coupling effect due to the transfer of shaft shear loading, and thus represents a significant improvement in the prediction of load deflections of drilled shafts.
Load Carrying Capacity of Back-to-Back Reinforced Soil Walls
Yoo, Chung-Sik ; Kim, Sun-Bin ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 41~52
This paper concerns the load carrying capacity of back-to-back reinforced soil wall for use in roadway and railway construction. Two test conditions, designed with due consideration of the FHW A design guideline, were first developed and a number of cases having different reinforcement lengths were tested under a surchage loading until failure. The results indicated that for cases in which two sides of reinforcements do not overlap, the wall behavior was similar to those of single wall. For cases in which the reinforcements overlap each other, on the other hand, the load carrying capacity of the wall significantly decreased when reinforced with reinforcement layers having lengths less than 50% of the wall height.
Relation between Cone Tip Resistance and Deformation Modulus of Cemented Sand
Lee, Moon-Joo ; Choi, Sung-Kun ; Choo, Hyun-Wook ; Lee, Woo-Jin ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 53~63
In this study, the cone tip resistances of cemented sand are measured by performing a series of miniature cone penetration tests in large calibration chamber, and the relations with constrained modulus, unconfined compressive strength, and shear strength of cemented sand are suggested. Experimental results show that both the cone tip resistance and constrained modulus of sand increase with increasing cementation effect as well as relative density and confining stress. However, it is observed that the relative density and confining stress have more significant influence on cone tip resistance than constrained modulus of cemented sand. Since the cone penetration into the ground induces the damage of cementation, the cone tip resistance can't properly reflect the cementation effect of sand. An analysis based on the constrained modulus shows that the measured cone tip resistance underestimates the deformation modulus of cemented sand by about
. In addition, this study establishes various relationships among the above soil properties from the regression analysis.
Engineering Application of Direct Shear Box Test for Slope Stability Problem
Ikejiri, Katsutoshi ; Shibuya, Satoru ; Jung, Min-Su ; Chae, Jong-Gil ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 65~73
In the current practice for slope stability problem in Japan, the shear strength,
, mobilized along the failure surface is usually estimated based on an empirical approximation in which the cohesion, c, is assumed to be equal to the soil thickness above the supposed slip surface, d(m). This approximation is advantageous in that the result of stability analysis is not influenced by the designers in charge. However, since the methodology has little theoretical background, the cohesion may often be grossly overestimated, and conversely the angle of shear resistance,
, is significantly underestimated, when the soil thickness above the supposed slip surface is quite large. In this paper, a case record of natural slope failure that took place in Hyogo Prefecture in 2007, is described in detail for the case in which the shear strength along the collapsed surface was carefully examined in a series of direct shear box (DSB) tests by considering the effects of in-situ shear stress along the slip surface. It is demonstrated that the factor of safety agrees with that of in-situ conditions when the shear strength from this kind of DSB test was employed for the back-analysis of the slope failure.
Shear Strength Characteristics of Recycled-Aggregate Porous Concrete Pile for Soft Ground Improvement
Yoon, Gil-Lim ; Yoon, Yeo-Won ; Kang, O-Ram ; You, Seung-Kyong ; Lee, Kyu-Hwan ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 75~84
Recycled-aggregate porous concrete pile (RAPP) which forms a composite ground is one of new ground improvement techniques. In this paper, triaxial compression tests are carried out to investigate the shear strength characteristics of RAPP-Clay composite samples. The main purpose of the tests was to investigate the effects of area replacement ratio (
) on behaviors of RAPP-Clay samples during shearing. Also, triaxial compression tests using Sand-Clay composite samples were performed to compare with the behaviors of RAPP-Clay samples. The test results showed that the friction angle and cohesion of the RAPP-Clay composite were
, respectively, whereas those of sand-clay composite samples were 26~35 degree of friction angel and
Evaluation of Influencing Factors on Settlement Behavior of Very Soft Ground with Reinforced Surface
You, Seung-Kyong ; Lee, Jong-Sun ; Ham, Tae-Gew ; Yang, Kee-Suk ; Cho, Sam-Deok ; Choi, Hang-Seok ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 85~92
It is necessary to develop a rational design method for surface reinforcement of very soft ground because most current design works rely on merely crude empirical correlations. In this paper, the mechanical behavior of very soft ground that is surficially reinforced was investigated with the aid of a series of numerical analyses. Several material properties of each dredged soft ground, reinforcement and backfill sand mat have been exercised in the numerical analysis. The result of numerical analysis was compared with those of the laboratory model test. Through the matching process between the numerical and experimental result, it is possible to determine representative material properties of the dredged soft ground, reinforcements and backfill sand mat. These verified material properties permit to evaluate the effect of the stiffness of reinforcement and the thickness of sand mat on the overall deformation of the reinforced soft ground.
Investigation on Support Mechanism of Geogrid-Encased Stone Columns in Soft Ground
Yoo, Chung-Sik ; Kim, Sun-Bin ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 93~101
This paper presents the results of numerical investigation on support mechanism of geogrid-encased stone columns for use in soft ground improvement. A number of cases were analyzed using a 3D stress-pore pressure coupled model that can effectively model construction sequence and drainage as well as reinforcing effects of geogrid-encased stone columns. The results indicated that the geogrid encasement provides additional confinement effect that reduces vertical stress in the soft ground, thus resulting in less excess pore water pressures and associated settlement. Also revealed was that such a confinement effect depends on encasement length and stiffness of geogrid. It is also shown that there exist critical encasement length and stiffness of geogrid for a given condition.
Compressibility and Stiffness Characteristics of Vanishing Mixtures
Truong, Q. Hung ; Eom, Yong-Hun ; Yoon, Hyung-Koo ; Lee, Jong-Sub ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 103~111
Soils naturally contain grains of different minerals which may be dissolved under chemical or physical processes. The dissolution leads changes in microstructure of particulate media, such as an increase in local void or permeability, which affects the strength and deformation of soils. This study focuses on the small strain stiffness characteristics of vanishing mixtures, which consist of sand and salt particles at different volume fractions. Experiments are carried out in a conventional oedometer cell (Ko-loading) integrated with bender elements for the measurement of shear waves. Dissolutions of particles are implemented by saturating the mixtures at various confining stresses. Axial deformation and shear waves are recorded after each loading stage and during dissolution process. Experimental results show that after dissolution, the vertical strain and the void ratio increase, while the shear wave velocity and small strain shear modulus decrease. The decrease of the velocity results from the void ratio increase and particle contact decrease. The process monitoring during dissolution of the particles shows that the vertical strain dramatically increases at the beginning of the saturation process and converges after vanishing process finishes, and that the shear wave velocity decreases at the beginning and increases due to the particle reorientation. Specimens prepared by sand and salt particles are proved to be able to provide a valuable insight in macro structural behaviors of the vanishings mixtures.
Verification of Frequency-Dependent Equivalent Linear Method
Jeong, Chang-Gyun ; Kwak, Dong-Yeop ; Park, Du-Hee ;
Journal of the Korean Geotechnical Society, volume 24, issue 12, 2008, Pages 113~120
One-dimensional site response analysis is widely used to simulate the seismic site effects. The equivalent linear analysis, which is the most widely used type of site response analysis, is essentially a linear method. The method applies constant shear modulus and damping throughout the frequency range of the input motion, ignoring the dependence of the soil response on the loading frequency. A new type of equivalent linear analysis method that can simulate the frequency dependence of the soil behavior via frequency-strain curve was developed. Various forms of frequency-strain curves were proposed, and all curves were asserted to increase the accuracy of the solution. However, its validity has not been extensively proven and the effect of the shape of the frequency-strain curve is not known. This paper used two previously proposed frequency-strain curves and three additional curves developed in this study to evaluate the accuracy of the frequency-dependent equivalent linear method and the influence of the shape of the frequency-strain curves. In the evaluation, six recordings from three case histories were used. The results of the case study indicated that the shape of the frequency-strain curve has a dominant influence on the calculated response, and that the frequency dependent analysis can enhance the accuracy of the solution. However, a curve that results in the best match for all case histories did not exist and the optimum curve varied for each case. Since the optimum frequency-strain curve can not be defined, it is recommended that a suite of curves be used in the analysis.