• Proceedings of the Korean Geotechical Society Conference
• /
• 1992.10a
• /
• pp.137-144
• /
• 1992

This paper reports a case study of dynamic consolidation. The objective of the study is to evaluate the effectiveness of ground improvement at the site for Hyundai Petrochemical Compound constructed at Daesan-Myeon, Seosan-Gun in the western shores of Korea. The site ground was prepared by filling on the existing soft marine deposit which consists of a loose granular soil layer and a medium stiff clay layer. For the stabilization of site ground, the compaction was executed in three different procedures with same pounder weigh, drop height and imprint spacing. The post investigation showed that the object was successfully achieved indicating a significant increase of bearing capacity of the treated ground. In this study the effectiveness of dynamic consolidation is evluated for various factors the applied energy, temping sequences, the radial distance from the imprint location and the depth of bed rock.

• Journal of the Korean Geosynthetics Society
• /
• v.4 no.3
• /
• pp.45-52
• /
• 2005

Most marine structures are constructed on very soft soil, soil improvements are needed for the area of road, buildings. In this paper, some considerations of several case studies on soil placement method after geotextile placement, known as surface treatment, are done. Considerations of strength applicability on the advanced construction method of sand and soil placement are proposed in this paper. Typical tensile strength of geotextile used in the surface soil stabilization method is 15t/m, and thickness of sand and soil placement between 1.6m and 3.1m. Undrained shear strength of soft clay layer ranges $0.2{\sim}1.2t/m^2$. In order to minimize the difficulties which include soil disturbance, soft soil gush and overturn of vertical drain installation rig more studies are needed.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.03a
• /
• pp.349-356
• /
• 1999

In general, the term soft ground includes clayey soils, which have large compressibility and small shear resistance due to the external load. All process of consolidation in compressible soils can be explained in terms of a transfer of load from an incompressible pore-water to a compressible soil structure. Therefore, one of the most important subjects about the characteristics of the time-dependent consolidation of the clay foundation by the change of load may be the presumption of the final settlement caused by consolidation and the degree of consolidation according to the time. The problems of discontinuous layer interface are very important in the algorithm and programming for the analysis of multi-layered soils using a numerical analysis, finite difference method. Better results can be obtained by the Process for discontinuous layer interface, since it can help consolidation analysis to model the actual ground. The purpose of this paper Provides an efficient computer algorithm based on numerical analysis using finite difference method(F.D.M.) which account for multi-layered soils to determine the degree of consolidation and excess pore pressures relative to time and positions more realistically.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.4
• /
• pp.57-67
• /
• 1999

In conventional stability analysis of embankment on soft clay ground, an averaged undrained shear strength$(s_u)$ for the depth of clay layer is usually used. Also, all applied load is assumed to an immediate load for simplicity of analysis. The load in the field, however, increases gradually. Undrained shear strength increases during loading due to consolidation of clay ground. In this study, the stability analysis program(RSI-SLOPE) is developed. By using this program, it is possible to consider the rate of strength increase according to the elapsed time of consolidation and the depth of clay ground. And the rested duration for consolidation and gradually increased load can also be considered. Using the examples of some embankments, the critical embankment heights calculated by RSI-SLOPE program are compared with those by PCSTABL without the considerations of gradually increased load and rate of strength increase. In addition, this study contains analysis and comparison about the influence of coefficient of consolidation$(c_u)$ and drainage distance$(H_{DR})$ in the embankment design. RSI-SlOPE program may be useful for more effective and accurate embankment design.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.577-584
• /
• 2002

We have employed two methods to remove slime at the end of the sampler in clay layers. The first method is a sampling process that harnesses low pressure to clean up the ground around the sampler tip. The second method, in consideration of a disturbed layer, involves a technique of inserting the sampler 50 cm deep into the ground before cleaning up the verge of the sampler by using high pressure. Physical and mechanical properties of these two methods have been compared and analyzed to investigate how different sampling methods affect degree of disturbance. The first method shows little disturbance since the unconfined compression test results in quite greater E$\_$50//q$\_$u/ in the first method than in the second method. On the other hand, the consolidation test results in a slightly greater compression index in the second method than in the first method, when their indexes are compared in the same depth. This suggests that the second method demonstrates less disturbance than the first method does. It is assumed that the second method may reduce disturbance slightly, However, we suspect that choosing any of the two methods would not obtain a considerable difference in sampling.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.5
• /
• pp.179-186
• /
• 2005

Each static and cyclic load test was performed in a laboratory model test. As a result, ground displacement decreased and bearing capacity of the soil increased owing to the sheer strength of geosynthetics in general. In addition, numerical analysis was operated using Mohr-Coulomb, Modified Cam-Clay models, and FLAC 4.0 2D and compared with the laboratory model test. The results were shown to be of a great difference because the existing equations had not considered the characteristics that sheer strength increases with a load increment. Therefore, this paper proposes an equation of cable elements considering an effect of load given through repeated tests.

• Geomechanics and Engineering
• /
• v.2 no.3
• /
• pp.191-202
• /
• 2010

The porosity (including the specific surface area and pore volume-diameter distribution) of montmorillonitic soft rock (MSR) was studied experimentally with an electrochemical treatment, based on which the change in porosity was further analyzed from the perspective of its electrokinetic potential (${\zeta}$ potential) and the isoelectric point of the electric double layer on the surface of the soft rock particles. The variation between the ${\zeta}$ potential and porosity was summarized, and used to demonstrate that the properties of softening, degradation in water, swelling, and disintegration of MSR can be modified by electrochemical treatment. The following conclusions were drawn. The specific surface area and total pore volume decreased, whereas the average pore diameter increased after electrochemical modification. The reduction in the specific surface area indicates a reduction in the dispersibility and swelling-shrinking of the clay minerals. After modification, the ${\zeta}$ potential of the soft rock was positive in the anodic zone, there was no isoelectric point, and the rock had lost its properties of softening, degradation in water, swelling, and disintegration. The ${\zeta}$ potential increased in the intermediate and cathodic zones, the isoelectric point was reduced or unchanged, and the rock properties are reduced. When the ${\zeta}$ potential is increased, the specific surface area and the total pore volume were reduced according to the negative exponent law, and the average pore diameter increased according to the exponent law.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.1
• /
• pp.21-29
• /
• 2003

In this study, practical guidelines to check the possibility of some lateral movement of piled abutment were investigated. In these tests, both the depth of soft clay and the rate of embankment construction are chosen to examine the effect on lateral soil movements. The depth of soft clay layer varies from 5.2 m to 11.6 m, and the rate of embankment construction has two types : staged construction(1m/30days, 1m/15days) and instant construction. Various measuring instruments such as LVDTs, strain gauges, pressure cells, and pore pressure transducers are installed in designed positions in ordo. to clarify the soil - pile interaction and the short and long term behavior f3. piled bridge abutments adjacent to surcharge loads. The validity of the proposed guidelines by centrifuge test was compared with the observed performance by lateral movement index, F(Japan Highway Public Corporation) and modified I index(Korea Highway Corporation). Based on the results obtained, the critical values off and modified I, as a practical guidelines, are proposed as 0.03 and 2.0, respectively.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.11
• /
• pp.113-122
• /
• 2006

Although a number of static pile load tests have been performed in this country, re-consideration on the interpretation and loading method is needed, because of their less usefulness in practice. For this study, a static loading testing was performed for a long instrumented PHC pile, which was installed in sand layer overlying thick soft clay. The shaft resistance of the pile had been monitored for a long time after installation, and then the static load testing was performed by the quick load test, unlike the recent Korean practice. Using the measured data, the elastic modulus of pile, residual stress and true resistance on the pile were determined. In the event, it was found that the residual stress on the pile, which remained prior to the static loading, significantly affects the shaft and toe resistances. Also, it was realized that the setup effect for the long pile is significant.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.10a
• /
• pp.497-508
• /
• 2006

Busan-Geoje Fixed Link, total length of 8.2km, consist of bridge and immersed tunnel connects Gaduk island, Busan and Jangmokmyon, Geoje, in extension of the $58^{th}$ local road. The immersed tunnel, a total length of 3.7km within Busan-Geoje Fixed Link, was planed first timein domestic but the deep water depth like maximum of 50m with offshore conditions and the 35m thickness of soft clay layer under the immersed tunnel, migth be some problems like the differential settlement during or after works. So it was designed to install SCP(Sand Compaction Pile) column partially to improve the soft ground under the immersed tunnel. In this paper, it is presented to illustrate the design including ground condition under the immersed tunnel, improvement design, upheaval shape and ratio due to SCP test construction.