Younguk Kim

Effect of Ultrasound on Surfactant-Aided Soil Washing

The use of ultrasound as an enhancement mechanism in the surfactant-aided soil-washing process was examined by conducting desoption tests of soils contaminated with naphthalene or diesel-oil. The experiments were conducted to elucidate the effect of ultrasound on the mass transfer from soil to the aqueous phase using naphthalene-contaminated soil. In addition, the use of ultrasound for the diesel-oil-contaminated soil was investigated under a range of conditions of surfactant concentration, sonication power, duration, soil/liquid ratio, particle size and initial diesel-oil concentration. The ultrasound used in the soil-washing process significantly enhanced the mass transfer rate from the solid phase to the aqueous phase. The removal efficiency of diesel-oil from the soil phase generally increased with longer sonication time, higher power intensity, and large particle size.

Effect of Ultrasound on Dewaterability of Sewage Sludge

In this study, we investigate the effect of ultrasound on the dewaterability of sewage sludge. The investigation involves laboratory experiments, which were conducted under a broad range of conditions, including energy levels of ultrasonic waves, treatment time, and pH. Results of the study show that ultrasound enhances dewaterability significantly. The degree of enhancement varies with sonication energy, treatment time, and the amount of treated sludge.

Field and Laboratory Investigation of Pullout Resistance of Steel Anchors in Rock

AbstractThis paper presents a field and laboratory investigation of pullout resistance of steel anchors in rock. The field testing involved pullout tests of six steel anchors installed in rock by gravity grouting and pressure grouting. The laboratory testing involved unconfined axial compression tests of six grout specimens prepared in custom-made molds using the two grouting methods to investigate the effect of grouting method on the mechanical properties of grout. The pressure-grouted specimens had a higher density and compressive strength, which was a result of their denser microstructure with significantly fewer and smaller voids from air bubble inclusions than the gravity-grouted specimens. The field pullout tests suggest a progressive failure mechanism, which was manifested through the progressive elongation of the bond zone. The pressure-grouted anchors yielded higher pullout resistance than did the gravity-grouted anchors. The increase in rock-grout bond strength from pressure grouting is likely d...

Experimental Investigation of Acoustically Enhanced Dewaterability of Unconsolidated Soils

The acceleration of water content reduction by vibrational energy was investigated with a series of laboratory tests. Vibration was generated with a poly(vinylidene fluoride) (PVDF) film as a flexible transducer at various frequencies. Test conditions included the power and duration of sonic energy, and the soil type. Test results showed a significant increase in dewaterability when ultrasound was applied. The time required for the outflow of the same amount of water was shorter for the sonicated conditions. The degree of enhancement varied with the test conditions. Using the test results, we discuss the potential development of a new method that can reduce the dewatering period.

Setting up Relationship between Pull-out Resistance of Helical Anchor and Rotational Penetration Torque for Methodology Development

This study evaluated the potential of methodology development of the helical type anchor for soft ground applications. The rotational penetration of the helix structure might make construction-steps easy without the soil spitting and reusable rods could reduce the material cost. Removal of the anchors would be simple as a construction, which can be named the removal anchor. The anchoring resistance after construction is strongly related to the number of helixes resulting in a concise design process. The investigation involved a chamber test with soft soils. In the test, a specially designed and fabricated helical anchor and torque-driver were used to obtain the maximum pull-out resistance of the anchor after rotational penetration. As a result of the tests, The rotational torque and pull-out resistance have a proportional relationship with the strength of the prepared soils. Within the range of the study, the torque of the anchor penetrating increased with increasing pull-out resistance.

Effect of Gap grade on Shear Strength of sandy soil

Soils with various particle sizes generally show good shear strength. Some soils have a relatively strong resistance to shear failure in spite of narrow particle distribution, such as gap grading. Based on this example, it can be inferred that appropriate arrangements of particle size in soils might result in an increase in shear strength. This study investigates the strength variation of soils with respect to the particle size distribution. Gap, well, and uniform graded soils were prepared with a desired ratio, and a wide range of direct shear tests were done using the prepared samples. The test results show that there is a strong relationship between the particle size ratio and internal frictional angle. Gap graded soil has a greater frictional angle than a well-graded sample, even when specimens have the same maximum particle size, which is also the case for the uniform grade specimen. The results have potential for developing a methodology for stronger soils through a simple manipulation of particle size distribution.

Use of amphiphilic triblock copolymers for enhancing removal efficiency of organic pollutant from contaminated media

We have studied amphiphilic triblock copolymers poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-b-PPG-b-PEG) and poly(propylene glycol)-b-poly(ethylene glycol)-b-poly(propylene glycol) (PPG-b-PEG-b-PPG) as possible substitutes for sodium dodecyl sulfate as anionic surfactants for the removal of hydrophobic contaminants. The triblock copolymers were compared with sodium dodecyl sulfate in terms of their abilities to remove toluene as hydrophobic contaminant in fuel, and the effects of polymer structure, PEG content, and concentration were studied. The PEG-b-PPG-b-PEG copolymer containing two hydrophilic PEG blocks was more effective for the removal of hydrophobic contaminant at extremely high concentration. We also measured the removal capabilities of the triblock copolymers having various PEG contents and confirmed that removal capability was greatest at 10% PEG content regardless of polymer structure. As with sodium dodecyl sulfate, the removal efficiency of a copolymer has a positive correlation with its concentration. Finally, we proposed the amphiphilic triblock copolymer of PPG-b-PEG-b-PPG bearing 10% PEG content that proved to be the most effective substitute for sodium dodecyl sulfate.

A Field Investigation of Pullout Resistance of Steel Anchors in Rock

This paper presents a field investigation of pullout resistance of steel anchors in rock. The field testing involves pullout tests of six steel anchors installed in biotite gneiss rock by gravity grouting and pressure grouting methods. The field pullout tests suggest a progressive failure mechanism, which was manifested through the progressive elongation of the bond zone. The pressure-grouted anchors yielded higher pullout resistance than did the gravity-grouted anchors. The increase in rock-grout bond strength from pressure grouting is likely due to a combination of several factors including the resultant higher grout strength, higher rock-grout contact stresses, and grout injected under pressure into the fractures/fissures that existed in the bedrock.

Case Studies of PSDDF for Phased Placement of Dredged Soils

Use of Terzaghis one-dimensional consolidation theory is not suitable for consolidation of highly deformable soft clays such as dredged soils. To model this condition, it is necessary to consider non-linear finite strain consolidation behavior, i.e., changes in compressibility and permeability with increasing stress. A one-dimensional non-linear finite strain numerical model, Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill (PSDDF), has been used to predict the stress-dependent settlement of fine-grained dredged materials. In this paper, two case studies of using PSDDF are discussed to illustrate the applicability and accuracy of PSDDF. The first case study involves PSDDF simulations of laboratory-phased placement of a marine clay dredged from Busan, Korea. PSDDF results are in good agreement with the corresponding results of the laboratory large strain consolidation tests. The other involves estimating the service life of the Craney Island Dredged Material Management Area near Norfolk, Virginia, in the United States. The excellent agreement between measured and calculated values shows that PSDDF is a reliable tool for predicting settlement of dredged material.

An Experimental Study on the Behavior of Composite Ground Improved by SCP and GCP with Low Replacement Ratio

Abstract This paper presents the results of laboratory tests conducted to investigate the effectiveness of applying methodology of a sand compaction(SCP) and a gravel compaction pile(GCP) on soft ground. The test conditions involved relatively low replacement ratios (=10, 20, and 30%) of a pile to unit cell at 1g (gravity acceleration) level. Results revealed that GCP significantly enhanced bearing capacity, settlement reduction, and consolidation rate compared with SCP. Key Words : SCP, GCP, Low replacement ratio, Bearing capacity, Settlement * Corresponding Author : Wan-Kyu Yoo (Korea Institute of Construction Technology)Tel: +82-31-336-8837 email: lyu5553@hanafos.comReceived October 24, 2012 Revised February 1, 2013 Accepted February 6, 2013 1. 서론 해상 또는 해안의 연약지반에 구조물을 축조할 때 지반개량을 목적으로 모래다짐말뚝(sand compaction pile, 이하 SCP), 자갈다짐말뚝(gravel compaction pile, 이하 GCP) 또는 쇄석기둥(stone column) 등의 공법을 적용할 수 있다. 이들 공법은 연약지반에 골재를 다짐하면서 압입하여 말뚝을 조성하는 공법으로 점토지반에 적용할 때에는 주로 지반의 전단강도 및 지지력 증대, 측방변위 억제, 압밀침하 저감 등의 효과를 목적으로 한다[1, 2]. 이러한 공법들 가운데 국내에서 가장 많은 시공실적을 보이며 널리 사용된 SCP공법의 경우에는 모래 자원의 고갈, 가격상승 및 다짐말뚝 품질유지에 어려움이 있는 등 문제점이 있다[3]. 이에 따라 대체 공법으로 쇄석 또는 자갈을 말뚝의 재료로 사용하는 GCP공법에 대한 관심과 시공실적이 증가하였다. SCP와 GCP 등 골재 말뚝으로 보강된 지반은 복합지반으로 고려할 수 있으며 이러한 복합지반의 거동특성은 골재의 종류, 치환율(