11. The stressstrain behavior of partially saturated sand

Sangseom Jeong, Sooyoung Kwon, Sooil Kim
Departement of Civil Engineering College Of Engineering, Yonsei University, 1996
Abstract
The behavior of partially saturated sand was investigated by using an automated triaxial testing device. The
stressstrain behavior of partially saturated sand was compared with the behavior of fully saturated sand prior
to failure and behavior at failure under undrained compression condition. The samples are chosen from a range
of particle size of #20#40, #40#60, #60#200, respectively and are molded to have two different relative
densities of 35% and 80%. The degree of saturation is controlled by varying pore water pressure parameter B.
Based on the experimental results, it is shown that the slope of modified failure envelope line(a¡¯) and the
modified effective cohesion( c¡¯) were not changed for both partially and fully saturated soil up to the point of
critical capillary rise. However, in the case where the capillary rise exceeds the critical value, difference in soil
property between the pa¥ðially and the fully saturated soil is observed and this differ¶§ce is greater as the
capillary rise is increased.



10. The behavior of dry Sand under dymunic loading  a study on the vertical vibration 

Sooil Kim, Sangseom Jeong, Younghoon An
Journal of the Korean Geotechnical Society, Vol.11, (4), 1995
Abstract
The dynamic behavior of dry sand under different vibration conditions is studied through laboratory experiments. Sinusoidal and random vibration experiments of sand are carried out in vertical direction under various surcharge loads.
Five different sand 8¾ønples are selected for the experiment. They are composed of four differentsize samples of particles and one sample which is simulated the field condition. In case of sinusoidal vibration, the change in relative density is measured with acceleration levels. To produce an acceleration. the vibration amplitude is maintained within the range of 0.4nm¡0.6mm and the vibration frequency is changed within the range of 3Hz ¡40Hz.
In case of random vibration. the combined sinusoidal acceleration is produced by a random vibration generator and the change in relative density is measured by an accelerometer.
Based on the experimental results, it is found that the sandy soil is compacted to 94% ¡99% of relative density by vertical acceleration and the peak acceleration producing the maximum relative density is proportional to the difference between maximum and minimum void ratios. It is also found that the effect of surcharge loading : the greater the surcharge loading, the larger the change in relative density and the greater the acceleration required to change the relative density .



9. Development of analytical method for laterally loaded pile groups

Sooil Kim, Sangseom Jeong, Sangwon Lee
Journal of the Korea Civil Engineers Society, 1995
Abstract
In this study, a computer program to predict the behavior of laterally loaded single pile and pile groups was developed by using a finite difference method and a matrix structural analysis in which the soils are modeled as nonlinear springs by a family of py curves for subgrade modulus. The emphasis was given to the lateral displacement of pile groups due to the soil condition and the cap rigidity. The analysis considering group effeet
was carried out for 2 x 2 and 3¡¿ 3 pile groups with the pile spacing 3.0B¡® 4.0B and 5.013. Based on the results obtained it is found that the overall distributions of deflection slope. moment. and shear force in a single pile give a reasonable results irrespective of cap connectivity conditions. It is also found that in pile groups. the prediction by present analysis simulates much better the general trend observed by the centrifuge tests than the numerical solution predicted by PIGLET.



8. The reliability of blast vibration equation

Sooil Kim, Sangseom Jeong, Hooyoun Cho
Journal of the Korea Civil Engineers Society, 1994
Abstract
Blast vibration equations proposed previously are investigated. Special attention is given to the blast vibration equation which shows the best fitting to the geologic condition of Korea. The fittness of proposed blast vibration equation is analyzed and examined using many field data measured in Korea. The prediction of blast vibration equation using field data was performed by linear regression analysis. Moreover, after the prediction of each blast vibration equ¾¾ ion, vibration velocity is recalculated on the basis of scaled distance at each equation¡® Reliability of regressioned blast vibration equation is observed by comparing predicted and measured velocity, which is divided into smallscale blasting of city and larges¾Êle blasting of quarry. Based on this study, the best
fitting equation to the Korean geologic condition is ROOT SCALING & CUBE ROOT SCALING proposed by USBM(United Nations Bureau of l\Iines). Also representative blast vibration equations depending on the different kinds of rock mass are proposed using measured and existing field data.



7. Consolidation analysis of soft clay by using modified consolidation theory

Sooil Kim, Junhwan Lee, Seungrae Lee, Sangseom Jeong
Journal of the Korea Civil Engineers Society, 1994
Abstract
Consolidation behavior on soft clay was investigated by using one and twodimensional analysis based on original and modified one dimensional consolidation theory. For the analytical model, the embankment was simulated by applying single or multisurcharge loading to the surface of soft clay. Based on the results obtained, it was found that the predicted settlement by one dimensional consolidation theory was most of the time higher than the observed one at the mid and especially lateralzone of embankment. When compared with two dimensional analysis, the result of modified one dimensional consolidation analysis showed almost similar trend to the observed one. Therefore even in case where proper selection of soil parameters, one dimensional consolidation theor¥ã like as modified one dimensional consolidation theory could be suggested due to its convenience.



6. The behavior of earth retaining structures using py curve with coupling

Sooil Kim, Sangseom Jeong, Buhmsoo Chang
Journal of the Korea Civil Engineers Society, 1994
Abstract
The behavior of earth retaining structure was investigated by considering coupling between soil springs in elastoplastic soil. For the computation of soil reaction, soil on both sides of walls was simplified as elastoplastic springs, and the required horizontal displacement to mobilize Terzaghi¡¯s active and passive state was applied to construct the py curve. Reliability on computer program developed is verified through the comparison between prediction and insitu measurements. Based on the results obtained, it is found that the prediction by using coupling between soil springs simulates well the general trend observed by the insitu measurements. It is also found that the horizontal displacement required for the active state gives a very small effect to the displacement
of walls in the sandy soil.



5. Vertical interaction factors of pile groups due to downdrag

Sangseom Jeong
Journal of the Korea Civil Engineers Society, 1994
Abstract
The group effect which causes different downdrag distribution in individual piles within the group was investigated by using a numerical analysis and an analytical study. The interaction factors due to group spacing and total number of piles in a group were estimated by using a three dimensional nonlinear finite element approach. Based on the results obtained, it is shown that the interaction factors of pile groups varies remarkably according to the group spacing, a major influencing parameter for the group effect. Also the downdrag prediction by the proposed method was compared with the other analytical methods through an example of calculations.



4. A simplified method for the calculation of skin friction on piles in soft clay

Sooil Kim, Sangseom Jeong, Sungyong Jung
Journal of the Korea Civil Engineers Society, 1994
Abstract
ºÎÁÖ¸é¸¶Âû·ÂÀº ¸»¶Ò¿¡ Downdrag ÇÏÁßÀ¸·Î ÀÛ¿ëÇÏ¿© ¸»¶ÒÀÇ ÁöÁö·ÂÀ» °¨¼Ò½ÃÅ³ »Ó ¾Æ´Ï¶ó °æ¿ì¿¡ µû¶ó¼´Â ¼È°èÇÏÁßÀÌ ±ØÇÑÁöÁö·ÂÀ» ³Ñ¾î¼¼ ±¸Á¶Àû ÆÄ±«¸¦ ¹ß»ý½ÃÅ°±âµµ ÇÑ´Ù. ±×·¯¹Ç·Î ÁÖ¸é¸¶Âû·ÂÀÇ Á¤È®ÇÑ »êÁ¤Àº ¸»¶ÒÀÇ ¼³°è ½Ã°ø ¹× ÇØ¼®½Ã ¾ÈÀüÀ² È®º¸ÀÇ °ü°ÇÀÌ¶ó ÇÒ ¼ö ÀÖ´Ù. ´Üµ¶¸»¶Ò¿¡ ¹ß»ýÇÏ´Â ÁÖ¸é¸¶Âû·ÂÀÇ Å©±â¿Í °Åµ¿À» ¿¹ÃøÇÏ±â À§ÇÑ ¸¹Àº ¹æ¹ýµéÀÌ ¿¬±¸µÇ¾î
¿Ô´Âµ¥ ÀÌ·¯ÇÑ ¹æ¹ýµéÀº Å©°Ô ÃÖ´ë Àü´Ü °µµ¹ý, Åº¼º ¶Ç´Â Åº¼Ò¼º ÇØ¼® ¹æ¹ý, ÇÏÁß Àü´Þ °î¼±À» ÀÌ¿ëÇÑ ¹æ¹ýÀÇ ¼¼ °¡Áö ¹üÁÖ·Î ºÐ·ùÇÒ ¼ö ÀÖ´Ù.
µû¶ó¼ º» ¿¬±¸¿¡¼´Â ¿¬¾à Áö¹Ý¿¡ ½Ã°øµÈ ´Üµ¶¸»¶Ò¿¡¼ ¹ß»ýÇÏ´Â ÁÖ¸é¸¶Âû·ÂÀ» ÇÏÁß Àü´Þ ÇÔ¼ö°³³äÀ» Àû¿ëÇÏ¿© ¸»¶ÒÁö¹Ý Á¢ÃË¸é¿¡ ÀÛ¿ëÇÏ´Â ÁÖ¿¬¸¶Âû·ÂÀ» Á¤È®È÷ »êÁ¤ÇÏ´Â ÇØ¼®Àû ¹æ¹ýÀ» Á¦½ÃÇÏ°í ÀÌ¸¦ Åä´ë·Î ½ÇÁ¦ ¼³°è¿¡ ¹Ý¿µÇÒ ¼ö ÀÖ´Â °£Æí¹ý¿Ã Á¦½ÃÇÏ°íÀÚ ÇÑ´Ù.



3. The behavior of silt due to volume deformation tendency

Sangseom Jeong
Journal of the Korea Civil Engineers Society, 1993
Abstract
The behavior of pure silt was investigated by using an automated triaxial testing device. The stressstrain behavior of silt due to the volume deformation tendency was compared with the behavior of clay prior to failure and behavior at failure under monotonic undrained compression and extension conditions. A pure silica flour was chosen to form samples. The isotropically normallyconsolidated samples with 450 kPa of effective mean confining pressure and overconsolidated samples through unloading were tested. Based on the experimental results, it was qualitatively identified that the undrained strength of normallyconsolidated silt increases due to its dilatant nature which is not seen in clay. Also the overconsolidated silt shows a significantly different behavior under the monotonic loadings due to the volume deformation tendency.



2. Downdrag on a single pile and pile groups

Sangseom Jeong
Journal of the Korea Civil Engineers Society, 1993
Abstract
The downdrag on a single pile and on pile groups was examined by using a numerical analysis and an analytical study. The overall obective of the present study was given to the magnitude and distribution of the downdrag forces on piles within a group. The case of the single pile was analyzed by developing a closed form solution. Subsequently the response of groups was investigated by using a detailed numerical approach. Based on the results, it is found that the downdrag load of piles in a group is much smaller than that of a single pile. Also, a simple method is proposed to design groups of 9 to 25 piles with spacingtodiameter ratios varying from 2.5 to 5.0 for downdrag loads.



1. The stress  strain behavior of a pure silt compared with sand and clay

Sangseom Jeong
Journal of the Korean Geotechnical Society, Vol.9, (4), 1993
Abstract
The drained and undrained behavior of pure silt was investigated experimentally. Special attention was given to the stressstrain 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%, e¡£=0.68 and D,=:35%, e¡£=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.


