• Journal of the Korean GEO-environmental Society
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• v.5 no.1
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• pp.13-25
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• 2004

Granular compaction piles increase the load bearing capacity of the soft ground and reduce the settlement of foundation built on the reinforced soil. The granular compaction group piles also accelerate the consolidation of the soft ground and prevent the liquefaction caused by earthquake using the granular materials such as sand, gravel, stone etc. However, this method is one of unuseful method in Korea. In the present study, the optimum locations of granular compaction group piles using genetic algorithm are proposed. The results were shown that the bearing capacity was increased in the case concentrated on the central part of the group piles. Also, the optimum design for total weight of granular compaction group piles was carried out in consideration of the economical efficiency and parametric studies were performed to examine the effects of parameters at the design of granular compaction group piles.

• Structural Engineering and Mechanics
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• v.85 no.3
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• pp.381-391
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• 2023

The seismic performance of the tall building equipped with a tuned mass damper (TMD) considering soil-structure interaction (SSI) effects is well studied in the literature. However, these studies are performed on the nominal model of the seismic-excited structural system with SSI. Hence, the outcomes of the studies may not valid for the actual structural system. To address the study gap, the reliability theory as a useful and powerful method is utilized in the paper. The present study aims to carry out reliability analyses on tall buildings equipped with TMD under near-field pulse-like (NFPL) ground motions considering SSI effects using a subset simulation (SS) method. In the presence of uncertainties of the structural model, TMD device, foundation, soil, and near-field pulse-like ground motions, the numerical studies are performed on a benchmark 40-story building and the failure probabilities of the structures with and without TMD are evaluated. Three types of soils (dense, medium, and soft soils), different earthquake magnitudes (M_w = 7,0. 7,25. 7,5 ), different nearest fault distances (r = 5. 10 and 15 km), and three seismic performance levels of immediate occupancy (IO), life safety (LS), and collapse prevention (CP) are considered in this study. The results show that tall buildings built near faults and on soft soils are more affected by uncertainties of the structural and ground motion models. Hence, ignoring these uncertainties may result in an inaccurate estimation of the maximum seismic responses. Also, it is found the TMD is not able to reduce the failure probabilities of the structure in the IO seismic performance level, especially for high earthquake magnitudes and structures built near the fault. However, TMD is significantly effective in the reduction of failure probability for the LS and CP performance levels. For weak earthquakes and long fault distances, the failure probabilities of both structures with and without TMD are near zero, and the efficiency of the TMD in the reduction of failure probabilities is reduced by increasing earthquake magnitudes and the reduction of fault distance. As soil softness increases, the failure probability of structures both with and without TMD often increases, especially for severe near-fault earthquake motion.

• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.99-104
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• 2007

The deep soil mixing, on ground modification technique, has been used for many diverse applications including building and bridge foundations, port and harbor foundations, retaining structures, liquefaction mitigation, temporary support of excavation and water control. This method has the basic objective of finding the most efficient and economical method for mixing cement with soil to secure settlements through improvement of stability on soft ground. In this research, the experiments were conducted on a laboratory scale with the various test conditions of mixing method; the angle of mixing wing, mixing speed. Strength and shapes of improved soil of these test conditions of deep mixing method were analysed. From the study, it was found that the mixing conditions affect remarkably to the strength and shapes of improved soils.

• Journal of the Korean Geotechnical Society
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• v.39 no.6
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• pp.21-30
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• 2023

One of the methods for calculating unit skin friction of soft-rock-socket parts for cast-in-place piles involves the roughness measurement of the parts. The measurements are conducted during the excavation stage. A roughness measuring device is installed in the excavation hole and the unit skin friction is calculated from the measured surface roughness of the rock socket. Herein, the results of roughness measurement of rock-socket parts in cast-in-place piles and that of load transfer tests are analyzed and compared. The unit skin friction from the roughness measurements can be converted into unit skin friction corresponding to the displacement of a pile generated in a load transfer test. A reduction factor is given as R_f = -0.14n + 1.48.

• Journal of Korea Technology Innovation Society
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• v.19 no.1
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• pp.105-136
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• 2016

This paper analyzed the qualitative evaluation indicators of the SYSTEM sector of the LINC program, which aimed at strengthening ability of regional universities through the activities of industry-academia cooperation (IAC). By using interview data and the program reports of universities, this research explored the problems of the indicators and suggested improvement measures which could lead to performance creativity. According to research results, in university system reform for activating IAC, some improvements are required as follows: limiting excessive expansion of IAC-friendly faculty evaluation; and evaluating soft aspects in the reform of academic affairs. In relation to strengthening of ability of the IAC organization, the indicators need to be amended as follows: enhancing the role of channel of IAC Foundation; strengthening the function of planning team of the IAC Foundation; and inducing development of own model of universities for IAC. As regards expansion of IAC infrastructure, it is necessary to enlarge the manpower who can develop programs of the support center in the foundation and to secure of operators for effective operation of joint-using equipments. Therefore, the indicators are required to be upgraded, considering these improvement direction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.662-671
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• 2020

The uplift force acts directly on the foundation and causes a building to float to the upper ground. To examine the stability of a structure according to the uplift force, four sites (Paju, Anyang, Osan, and Gangneung) were selected, and sensors were installed on the foundations for the field tests. The rainfall characteristics were analyzed around June~September, and the changes in the water level of the adjacent river were considered. The maximum uplift force except for Gangneung did not exceed 72% of the water pressure when the groundwater level was up to the surface. On the other hand, the maximum uplift force in Osan was approximately 67%, but the reliability was slightly inferior because the difference from the average (46%) was large. The minimum uplift force was within 10% except for Anyang (~ 41%). At the Gangneung site on soft rock where the permanent drainage facility was installed before the measurement, the maximum and minimum uplift force was approximately 14% and 3.5%, respectively. Based on the measurement results, the possibility of overdesigning or underdesigning comes from the design by the hydrostatic pressure when the groundwater level is up to the surface.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.202-209
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• 2015

This study compared and analyzed the measurements of pullout load according to the depth of reclamation in the foundation, compaction ratio of soil, spiral diameter, and soil textures in an experiment with a model and reached the following conclusions: The comparison results of extreme pullout load between farm and reclaimed soil show that farmland soil recorded a score that was 1.2~3 times higher than that of reclaimed soil. The investigator measured pullout load in farmland and reclaimed soil and observed a tendency of rising extreme pullout load according to the increasing depth of reclamation and compaction ratio with a similar load-displacement curve between the two types of soil. Extreme pullout load made a greater increase by the rising size of diameter than the increasing depth of reclamation, also making a considerably bigger increase according to the rising compaction ratio than the other conditions. Therefore, the spirals bar is expected to be available in soft soil foundation, as well as farmland as increasing buried deep of foundations, compaction rate, diameter of the spiral, ect.

• Journal of the Korean GEO-environmental Society
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• v.12 no.3
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• pp.55-61
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• 2011

Song-Do international city is the area developed in large-scale land reclamation. Song-Do area consists of reclamation layer, sedimentary layer(loose silt, soft clay and sand alternating) and residual layer from the ground surface. Therefore, using pile foundation is inevitable to build structures safely. In this area, driven PHC piles have been generally constructed in terms of environmental and economic conditions. As a result of analyzing 4 sites in Song-Do district 5 and 7 recently, the method of driving pile has many problems because of existence of rigid soil in sedimentary layer and installation of more than 30m piles. In this case, when installing piles by drive after pre-boring up to appropriate depth, the results of constructability analysis were very good. And in the economic efficiency, although 4% of construction cost rose, it was a very slight increase in comparison with improvement of workability. In the case of the stability, more than 70% compared to the allowable stress of piles was satisfied through the load test. As a result, when PHC piles is installed in Song-Do district, the proper construction method is that piles are located at bearing layer after boring rigid sand layer.

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

• Proceedings of the Korean Geotechical Society Conference
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• 2000.02a
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• pp.1-11
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• 2000

The use of Compaction Grouting evolved in 1950's to correct structural settlement of buildings. Over the almost 50 years, the technology has been developed and is currently used in wide range of applications. Compaction Grouting, the injection of a very stiff, 'zero-slump' mortar grout under relatively high pressure, displaces and compacts soils. It can effectively repair natural or man-made soil strength deficiencies in variety of soil formations. Major applications of Compaction Grouting include densifying loose soils or fill voids caused by sinkholes, poorly compacted fills, broken utilities, improper dewatering, or soft ground tunneling excavation. Other applications include preventing liquefation, re-leveling settled structures, and using compaction grout bulbs as structural elements of minipiles or underpinning. In this paper, on the basis of the case history constructed in this year, a study has been performed to analyze the basic mechanism of the Compaction Grouting. Also, the effectiveness of the ground improvement and the bearing capacity of the Compaction Pile has been verified by the Cone Penetration Test(CPT) and Load Test. Relatively uniform Compaction grouting column could be maintained by planning the Quality Control in the course of grouting. And, the Quality Control Plan has been conceived using grout pressure, volume of grout and drilling depth.