• Geotechnical Engineering
• /
• v.9 no.3
• /
• pp.35-48
• /
• 1993

This paper was focused on the design and construction of stone columns as a method of reinforcements in slightly soft clay or loose silty sand overlying the firm strata. It was intended to find out the effects of soil improvement by field tests in Kwangmyoung Haan Site by comparing the test results performed before and after the installation of stone columns . The results of this experimental study are as follows : the hearing capacity was increased by 3.33 times and the SPT N -valued was increased by 3.9 times by installing the stone columns : the stone column method can cut down the construction cost almost 35% compared to the precast concrete pile method in economic viewpoints.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.8
• /
• pp.5-16
• /
• 2007

The stone column method is widely used in Europe as an alternative to conventional pile foundations. Several benefits of using the stone column method include sound performance, low cost, expediency of construction, and liquefaction resistance among others. Recently, geosynthetic-encased stone column approach has been developed to improve its load carrying capacity through increasing confinement effect. Although such a concept has been successfully applied in practice, fundamentals of the method have not been fully explored. This paper presents the results of an investigation on the load carrying capacity of geogrid-encased stone column using a series of 2D finite element analyses. A parametric study was then conducted for influencing factors such as effect of geogrid encasement, encasement length, geogrid strength, among others. The results of the analyses indicated improved short- and long-term load carrying capacity of the geogrid-encased stone column method has advantages over the conventional stone column method without encasing.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.613-620
• /
• 2002

Sand Compaction Pile(SCP) is a soil improvement method that a sand charge is introduced into the pipe, and the pipe is withdrawn part away while the sand pile is compacted and its diameter is enlarged. The sand used in this method should be of good quality. In Korea, crushed stone and washed sea sand are used frequently in SCP. However, use of these materials is restricted because of environmental problem and deficiency of supply. In the copper smelting process, about 0.7 million tons of copper slag are produced in Korea. The range of particle size distribution of copper slag is from 0.15mm to 5mm, so it can be a substitute for sand, and the relatively high specific gravity compared with the sand, is its characteristic. Copper slag is hyaline and so stable environmentally that in foreign country, such as Japan, Germany etc., it is widely used in harbor, revetment and offshore structure construction works. Therefore, in this study, the several laboratory tests were peformed to evaluate the applicability of copper slag as a substitute for sand of SCP. From the mechanical property test, the characteristics of sand and copper slag were compared and analyzed, and from laboratory model test, the strength of composite ground was compared and analyzed by monitoring the stress and ground settlement of clay, SCP and copper slag compaction pile. Specially, this study focused on the application of copper slag as sand substitute in SCP pilot tests based on laboratory tests results.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.3
• /
• pp.1-9
• /
• 2019

In this study, the effect of ground improvement was to be verified by granular compaction pile from the ground reclaimed with Fly Ash landfill site. The depth and strength parameters of the Fly ash layer was determined using the ground investigation and cone penetration test. And the STONE C program was used to predict the strength parameter, bearing capacity and settlement of the improved ground. As a result of the plate bearing test, the bearing capacity of improvement ground was higher than the design load and the settlement was smaller than the reference value. After the construction, the improvement effect by the cone penetration test was confirmed. The cone penetration resistance value($q_c$) increased by 250% to 500% and the effect was excellent.

• International Journal of Highway Engineering
• /
• v.12 no.4
• /
• pp.139-145
• /
• 2010

An integrity testing for stone columns was attempted using crosshole S-wave logging. The method is conceptionally quite similar to the crosshole sonic logging (CSL) for drilled piers. The critical difference in the logging is the use of S-wave rather than P-wave, which is used in CSL, because swave is the only wave sensing the stiffness of slower unbounded materials than water. An electro-mechanical source, which can generate reversed Swave signals, was utilized in the logging. The stone column was delineated using the S-wave travel times across the stone column, the S-wave velocity profile of the crushed stone($V_{cs}$-profile) and that of surrounding soil($V_s$-profile). In the calculation of $V_{cs}$-profile of the crushed stone, its friction angle and Ko (coefficient of lateral earth pressure at rest) are recommended to be used. The calculation of the column diameter is not much affected by the values of friction angle and Ko.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.38 no.1
• /
• pp.69-78
• /
• 2002

In order to examine the directional suitability of the axis direction of the fishing gear against the current, the experiments were carried out at the bamboo weir in Samchunpo water area from January, 2000 to September, 2001 The results of the study are as follows: In the experimental fishing gear constructed in the "V" shape, the range between two reference piles located at the entrance was 2.5m. The direction of bamboo weir′s axis was 355.5$^{\circ}$ The length of the left wing and those from the reference pile to the starting point of a curve were 106.0m, 7.5m, respectively. The length of the right wing and those from the reference pile to the starting point of a curve were 79.0m, 10.0m, respectively. Depths around the left and right stone wall that drove the steel pile were 5.0~6.5m and 6.5~9.5m, respectively. Also, depths on the bamboo weir′s axis and around the sack were 7.0~8.0m and about 8.0m, respectively. The maximum height of stone walls at the point of the left wing, the right wing and around the sack on the bamboo weir\` axis were 3.0m, 4.7m and 4.0m, respectively, Widths of stone walls at the point of both of the wings and around the sack on the bamboo weir\`s axis were 10.0~l4.0m, 22.0~25.0m, respectively. The averaging current direction on ebb tide was measured two times and it was 169.2$^{\circ}$ but the direction had about a 6.3$^{\circ}$ difference from the bamboo weirs axis. The maximum current speed appeared two to three hours later from the time of high tide and the current speed over 80.0cm/s lasted during about two Hours on the ebb tide In the case of a straight type wing In the bamboo weir, the eddy out of the left wing was comparatively big and the current on the right side from the bamboo weir′s axis had a tendency in turning to the right wing side. But in the case of a curve type wing, the eddy and tendency reduced significantly. It was thought that the experimental fishing gear was set suitably from the result of this simulation.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.4
• /
• pp.21-30
• /
• 2006

In this study, centrifuge model tests were performed to investigate the stress concentration ratio, bearing capacity and deformation modes of piles in clay ground improved by granular piles with two types of pile (CSCP, SCP) and various replacement ratios (0, 20, 40, 60%). According to the results of tests, the load ratio of ground improved by SCP and CSCP proportionally increased as replacement ratio increased. It shows that average normalized load of ground improved by CSCP is higher by about $8{\sim}21%$ than by SCP. As a result of rigid loading tests, it was evaluated that average stress concentration ratio of CSCP is higher than that of SCP. Only expansion failure occurred in CSCP, whereas SCP showed the expansion and shear failure simultaneously.

• Journal of the Korean Geosynthetics Society
• /
• v.6 no.1
• /
• pp.17-25
• /
• 2007

This study presents a modeling approach for geogrid-encased stone column(GESC) method which is widely used in Europe as an alternative to conventional pile foundations. Several benefits of using the stone column method include sound performance, low cost, expediency of construction, and liquefaction resistance, among others. Recently, geosynthetic-encased stone column approach has been developed to improve load carrying capacity through increasing confinement effect. The aim of this research is to establish a systematic approach for modeling of GESC and to form a database for the fundamentals of GESC. This paper presents details of 3D modeling of GESC together with the general behavior of GESC.

• Korean Journal of Heritage: History & Science
• /
• v.50 no.4
• /
• pp.222-251
• /
• 2017

This paper analyzes the characteristics of the ancient tombs discovered in the Gyeongju site and discusses the direction of the excavation. There are six special features of the wooden chamber tomb covered with stone in Gyeongju. First, confirmation of the above-ground type and the underground type burial mound. Second, confirmation of the construction such as the partition of mound and the pile of stone structure. Third, confirmation of the frontal part structure of the protect stone such as pebble-stone layer, boundary stone. Fourth, confirmation of the relationship before and after the mound. Fifth, the circumference and boundary of the confirmed(before 1990s) burial mounds were discovered, resolving the uncertainty. Sixth confirmation of the crowd unit tombs. By summing up these six features, it is possible to clearly divide the individual units and the crowd units of the Silla tombs. Confirmation of individual units and crowd units can clarify the size and scope of the tombs located by the concatenation and overlap. It is possible to get a glimpse of the formation process through the interrelationships between the two sides. The tombs are located in the upper-and-lower layer structure of the tombs and show selective site selection. When this formative process is rearranged, it is understood that the Gyeongju Silla Cemetery is formed through the course of four stages. It is anticipated that it will be possible to make selective projects in the excavation survey based on the confirmation of the individual unit and the crowd unit of the Silla ancient tombs and the formation process.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.20 no.2
• /
• pp.160-165
• /
• 2010

As the various industrial machinery has come into being by development of industrial technology, the productivity of the basic industrial machinery has improved. However, at the same time, noise from various industrial machinery disturbs the quiet environment. There are 35 kinds of the noise emission machinery defined in the noise and vibration control act according to the horse power and the number of machinery. These were classified in 1992, and the characteristics of the noise emission machinery may be different from the past one. So we need to investigate the characteristics of the noise emitted by machinery to control it rightly. We measured sound intensity of 32 noise emission machinery to calculate the sound power levels of those and investigated the characteristics of the sound power level of those according to the frequency. We found that the forging machine, concrete pipe and pile making machine, sawing machine, etc. are noisy. The generator, the concrete pipe and pile making machine, etc. emit the low frequency noise, but the molding machine, the stone cutter, the metal cutter, etc. emit the high frequency noise.