• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.281-292
• /
• 2008

Prefabricated Board Drains (PBDs) recently become more widely used than conventional sand drains in improving soft ground because the PBD is more time and cost effective. The performance of PBDs is affected by disturbance in the adjacent soil formation during inserting mandrels, the intrusion of fine particles into filter fabric, and necking of the drain by excessive lateral pressure especially occurring in very deep clay formation such as the Busan New Port site. In this study, the PBD with double-core is introduced, which seems to overcome the shortcomings of usual single-core PBDs. An in-situ test program was established in the Busan New Port site, in which a set of the double-core PBDs and the single-core PBDs was installed to compare the efficiency of each of the drains. The discharge capacity of the double-core and the single-core PBDs was compared for various confining pressures in the modified Delft test and the chamber test. A series of CRS consolidation tests was performed in order to obtain profiles of void ratio-effective stress and void ratio-permeability relationships in the Busan New Port site that are used as input date in performing a numerical program ILLICON. The numerically simulated settlements of ground surface in the test site are in good agreement with those of in-situ measurements. In addition, the performance of the double-core and single-core PBDs has been experimentally and numerically compared in this paper.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1630-1637
• /
• 2008

Jeju-do is a island formed by the volcanic activity and has more than 360 volcanic cones distributed widely along the long axis of the elliptically shaped island. The volcanic cones consist mainly of scoria, so called "Song-I" in the local dialect. In this study the chemical and soil mechanical properties of scoria being very different from those of the inland were investigated with the various tests. In the sieve-passing test the particle size of scoria had more than 10 of uniformity coefficient and gradation coefficient of 1 ~ 3, showing relatively homogenous distribution. Based on the uniformity classification, scoria was assorted into GW. In the large scale direct shear tested for measuring the mechanical strength of scoria the internal friction angle of red scoria was $37^{\circ}$ and that of black scoria was $36^{\circ}$. This indicated that there was no difference in the mechanical strength between two types of scoria. On the other hand, red and black scoria had $1.24{\times}10^{-3}$ to $3.55{\times}10^{-2}$ cm/sec of k values for the static water level permeability, thus being classified into a coarse or fine sand as compared with that representing the saturated soil. They also had 1.411 to $1.477\;g/cm^3$ of notably low $r_{dmax}$ values for the compaction test as compared with common soil, which was considered to be due to their low specific gravity and high porosity. In conclusion, the soil mechanic properties of scoria obtained from this study are thought to be very helpful for reducing lots of trial and error happening in the civil engineering construction.

• Korean Journal of Medicinal Crop Science
• /
• v.5 no.2
• /
• pp.119-125
• /
• 1997

This study was carried out to know the factors affecting rooting and growth in stem cutting of Ligusticum chuangxiong for mass propagation. The results indicated that : (1) Rooting and growth were better in perlite which has higher air permeability. (2) Sub-irrigation with 15min long with 30min interval was more favorable for growth. (3) Proper tempeature for rooting and growth ranged from $25^{\circ}C\;to\;30^{\circ}C$ while photoperiod had no effect on rooting and growth.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.3
• /
• pp.83-91
• /
• 2003

The electrokinetic technique has been applied to remove mainly the heavy metal and the ultrasonic technique to remove mainly organic substance in contaminated soil. In this study, the combined electrokinetic and ultrasonic remediation technique was studied far the removal of heavy metal and organic substance in contaminated soils. This study emphasized the coupled effects of electrokinetic and ultrasonic techniques on migration as well as remediation of contaminants in soils. The laboratory soil flushing tests combining electrokinetic and ultrasonic technique were conducted using specially designed and fabricated devices to determine the effect of both of these techniques. A series of laboratory experiments involving the simple, electrokinetic, ultrasonic, and electrokinetic & ultrasonic flushing test were carried out. A soil admixed with sand and kaolin was used as a test specimen, and Pb and ethylene glycol were used as contaminants of heavy metal and organic substance. An increase in out flow, permeability and contaminant removal rate was observed in electrokinetic and ultrasonic flushing tests. Some practical implications of these results are discussed in terms of technical feasibility of in situ implementation of electrokinetic ultrasonic remediation technique.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.10
• /
• pp.105-111
• /
• 2008

To improve the stability of levee structure, it is required to use good quality fill materials, intensive management, appropriate hydraulic structure and construction of cut-off wall. In particular, the most important factor of levee construction technology is to use bed sediment for its safety. In this study, seepage model test and numerical analysis were performed based on a standard section of levee recommended in the river design standard of korea (2005). The results of test and analysis show that most of the bed soil is a sand (SP in USCS), which does not satisfy the permeability criteria for levee materials ($< k=10^{-3}cm/sec$), thus for the safety of levee it is required to adopt a stabilizing method such as good quality soil mixing, water content control.

• The Journal of Engineering Geology
• /
• v.28 no.1
• /
• pp.101-115
• /
• 2018

This study was carried out to evaluate the effects of various filter conditions on unconfined aquifer (alluvial aquifer). We made model test device which has filter layer, pumping well and observation well which consist of sand layer and gravel layer to test. Step drawdown test and long term pumping tests were carried out using the device. The permeability characteristics of each test group were confirmed and the optimal yield was calculated. As a result of comparing the optimal yield of double filter and single filter in sand, dual-filter SD-300 was valued at 216.8 % higher final optimal yield than single-filter SS-300. Comparing the dual filter SD-300 and the single filter SS-100 with a thin filter layer, dual-filter SD-300 was valued at 709.2% higher final optimal yield than single-filter SS-300. As a result of analysis of optimal yield change over time, It was confirmed that the ratio of optimal yield of single filter and dual filter increase over time. In order to evaluate the long-term change in water intake efficiency, we considered the point at which the initial optimal yield was reduced by 50%. The dual filter SD-300 is about 351.1% higher than SS-300, which is the same thickness filter, and about 579.0% higher than SS-100. From these results, Assuming that the point at which the initial quantity of water intake is reduced to 50% is the well life, double filters are expected to increase their lifespan by about 3.5 times over single filters of the same thickness and by about 5.8 times over typical single filter. These results can be used to design wells to river bank filtration or filtered seawater. In addition, it is possible to clarify the effect of the double filter through the comparison with the future field test results.

• The Korean Journal of Petroleum Geology
• /
• v.4 no.1_2 s.5
• /
• pp.27-39
• /
• 1996

In the Cretaceous, the Gulf Coast Basin evolved as a marginal sag basin. Thick clastic and carbonate sequences cover the disturbed and diapirically deformed salt layer. In the Cretaceous the salinities of the Gulf Coast Basin probably matched the Holocene Persian Gulf, as is evidenced by the widespread development of supratidal anhydrite. The major Lower Cretaceous reservoir formations are the Cotton Valley, Hosston, Travis Peak siliciclastics, and Sligo, Trinity (Pine Island, Pearsall, Glen Rose), Edwards, Georgetown/Buda carbonates. Source rocks are down-dip offshore marine shales and marls, and seals are either up-dip shales, dense limestones, or evaporites. During this period, the entire Gulf Basin was a shallow sea which to the end of Cretaceous had been rimmed to the southwest by shallow marine carbonates while fine-grained terrigengus clastics were deposited on the northern and western margins of the basin. The main Upper Cretaceous reservoir groups of the Gulf Coast, which were deposited in the period of a major sea level .rise with the resulting deep water conditions, are Woodbinefruscaloosa sands, Austin chalk and carbonates, Taylor and Navarro sandstones. Source rocks are down-dip offshore shales and seals are up-dip shales. Major trap types of the Lower and Upper Cretaceous include salt-related anticlines from low relief pillows to complex salt diapirs. Growth fault structures with rollover anticlines on downthrown fault blocks are significant Gulf Coast traps. Permeability barriers, up-dip pinch-out sand bodies, and unconformity truncations also play a key role in oil exploration from the Cretaceous Gulf Coast reservoirs. The sedimentary sequences of the major Cretaceous reseuoir rocks are a good match to the regressional phases on the global sea level cuwe, suggesting that the Cretaceous Gulf Coast sedimentary stratigraphy relatively well reflects a response to eustatic sea level change throughout its history. Thus, of the three main factors controlling sedimentation (tectonic subsidence, sediment input, and eustatic sea level change) in the Gulf Coast Basin, sea-level ranks first in the period.

• Korean Journal of Soil Science and Fertilizer
• /
• v.45 no.6
• /
• pp.1222-1229
• /
• 2012

The total area of a reclaimed tidal soil distributed on the south-west coast is approximately 156,600 ha, and the soil contains high contents of sand and silt as well as highly saline. Most of the reclaimed tidal soils are used as a paddy due to bad permeability and high groundwater table, resulting in easy accumulation of salts on the soil surface by capillary rise. Therefore, resalinization may occur because of rise of groundwater table after desalinization. The researches related to the reclaimed tidal soil mainly focused on desalinazation while most of the researches completed were limited to yields of crop based on desalinazation. pH of old reclaimed tidal soil is neutral or less than 7 while that of newly developed reclaimed tidal soils is greater than 7, that cause N-fertilizer to be volatile as ammonia. Thus, the physical and chemical properties should be investigated to be used as an arable upland instead of a paddy soil due to change in government policy. We need to develop measures to make soils grow crops normally by identifying problems related to reclaimed tidal soils.

• The Journal of Engineering Geology
• /
• v.15 no.2 s.42
• /
• pp.105-121
• /
• 2005

Most of the landslides triggered by intensive rainfall on natural slope occur serious damages of human beings and properties. There have been many landslides since 1991 in Gyeonggi province. The influential factors are rainfall, topography, geology and soil properties. There were 660 landslides occurred by intensive rainfall as much as 250mm at Yongin and Anseong area from Tuly 19th to luly 21st,1991 This study surveyed location, topography, geology, geometry of the landslide and rainfall at the area and analyzed occurrence characteristics of the landslides. Most of the landslides occurred on the soil layer above the bed rock. They showed changes of landslide types from translational slides at the head part to flow at the central part. The landslides have relatively small magnitude of which length is shorter than 50m. In order to identify characteristics of landslides dependent on soil conditions, geotechnical properties of soil were evaluated by laboratory tests using soil samples which were collected on slided area and not-slided area. Soil properties of the slided area show high percentage of coarse material such as gravel and sand. However, soil of the not-slided area is mainly composed of fine material such as silt and clay. Permeability coefficients of the slided area are higher than those of the not-slided area.

• The Journal of Engineering Geology
• /
• v.17 no.1 s.50
• /
• pp.125-133
• /
• 2007

The environmental and geotechnical properties are investigated to the 8th landfill area made of only sewage sludge in Nanji-Do. To do this, the soils are sampled in this area, and leaching tests, heavy metal content tests, and so on are performed to research the environmental properties. As the result of heavy metal content tests, Pb, Zn, Cu, Ni, Cd and Cr were leached from the sewage sludge. Because the leaching concentration of Cu is more than the standard value of California state, Cu content have to bring down during the recycling of the sewage sludge. Meanwhile, a series of tests concerning specific gravity, liquid and plastic limits, compaction, permeability and shear strength is performed to research the geotechnical properties. The sewage sludge is consisted of sand, silt and clay, and is classified into non-organic silt or organic clay with 42.3% of plastic index. As the result of compaction test, it is expected that the compaction effect according to variation of water contents is low relatively because the dry unit weight is low and the curve of compaction forms flatness. Also, as the result of direct shear tests, the cohesion is $0.058kg/cm^2$, and the internal friction angle is $14^{\circ}$. Taking everything into consideration, the various problems are happening in case of recycling the sludge like the cover layer of landfill and so on because the compaction is bad, and the shear strength is low. Also, it is expected that the ground water pollution caused by leaching the heavy metal into the sludge. To do recycling the sewage sludge in this site, supplementary and treatment programs should be prepared.