Jaehun Ahn

Characterization of a Polyacrylamide Solution Used for Remediation of Petroleum Contaminated Soils

Biopolymers are viewed as effective and eco-friendly agents in soil modification. This study focuses on the wettability analysis of polyacrylamide (PAM) solutions for soil remediation. The contact angle, surface tension, and viscosity of PAM solutions were experimentally evaluated in air- and decane-biopolymer solution systems. Furthermore, a micromodel was used to investigate the pore-scale displacement phenomena during the injection of the PAM solution in decane and or air saturated pores. The contact angle of the PAM solution linearly increases with increasing concentration in air but not in decane. The surface tension between the PAM solution and air decreases at increasing concentration. The viscosity of the PAM solution is highly dependent on the concentration of the solution, shear rate, and temperature. Low flow rate and low concentration result in a low displacement ratio level, which is defined as the volume ratio between the injected and the defended fluids in the pores. The displacement ratio is higher for PAM solutions than distilled water; however, a higher concentration does not necessarily guarantees a higher displacement ratio. Soil remediation could be conducted cost-efficiently at high flow rates but with moderate concentration levels.

Coefficient of Subgrade Reaction for the Permeable Block and Base System at Korea GI and LID Center

The Permeable block pavement is one of the representative Low Impact Development (LID) techniques for innovative water management based on systems that can infiltrate usually over the surface. The material of each layer in permeable block pavements is often comprised of a granular material with very high porosity not like conventional pavements. However, unlike conventional pavements, researches on structural characteristics of permeable block pavement is insufficient yet. Therefore, in this study, as part of study to understand the structural characteristics of permeable block pavement and open graded aggregate that is used as base material of permeable block pavement, plate load test was carried out on two different pavement sites, site M and N. Site M is aggregate base sites and site N is permeable block pavement site. Based on the relationship between load and settlement that is obtained from the test, coefficient of subgrade reaction (k) was calculated. Through the relationship between load-settlement and k, structural characteristics were evaluated according to material differences of the pavements.

Small Strain Stiffness of Unsaturated Sands Containing a Polyacrylamide Solution

Sand improvements using organic agents have shown promising results. Polyacrylamide is one possible organic agent, which has been shown to influence the shear strength, stiffness, soil remediation, and erosion resistance of geomaterials. In this study, we explored the shear wave velocity (S-wave) and water retention curves of unsaturated sands containing polyacrylamide solutions. The shear wave velocity was measured during the water retention curve measurement tests according to the variation of the degree of saturation. The experimental setup was verified through comparison of the measured water retention curves with the published data. The results show that (1) the S-wave velocity of saturated sands increases with polyacrylamide concentration; (2) as the degree of saturation decreases, the S-wave velocity increases; (3) near the residual water (or polyacrylamide solution) saturation, the S-wave velocity increases dramatically; (4) as the degree of saturation decreases, the S-wave velocity at unsaturated conditions increases with any given water (or polyacrylamide solution) saturation, like the water retention curves; (5) the S-wave velocity increases with the increase in capillary pressure; and (6) the predicted S-wave velocity at a given degree of saturation is slightly overestimated, and the modification of the equation is required.

Back-Calculation of Soil-Water Characteristics Curve for Permeable Pavement Material Based on Infiltration Tests

Permeable pavement systems, an Low Impact Development technique, are widely used for pedestrian and bicycle roads, and parking lots, to relieve the flooding and enhance water cycle, which arises due to climate change and urbanization. However, due to lack of analytical means, permeable pavements are constructed most of time without knowing their performance in reducing runoff. In this paper, saturated permeability and porosity of a pervious concrete sample were experimentally estimated, and a set of infiltration model test was conducted; then, finally, the soil-water characteristics curve of the sample was back-calculated. In inverse analysis, van Genuchten model was selected, and Levenberg-Marquardt method was used for parameter searching algorithm. The results of soil-water characteristics curve presents the air-entry suction pressure is little below 1 kPa, and all the water expels at a suction pressure of 10 kPa. When compared to typical sands, the volumetric water content of pervious concrete drops more steeply with increasing suction pressure.

Compressibility and Thermal Characteristics of Plant Biomass Ashes

Biomass has become one of major sources of renewable energy, but, after combution, the ashes of biomass are not well recycled. The compressibility and thermal characteristics of biomass ashes were experimentally analyzed and compared to silica sand, in attempt to utilize the biomass ashes as sustainable construction material. The mean particle sizes of wood and sugarcane bagasse ashes were 0.15 mm and 0.04 mm, respectively; the particles were angular and had non-uniform array. The compressibility of biomass ashes were much larger than those of sands with the same initial loading; the thermal conductivity lower. In addition, the more saturated, the higher thermal conductivity. The compressibility and thermal characteristics of biomass ashes, reported in this paper, are for uniform materials that contain relative high void contents; the mixture of soil and biomass ashes, which has denser composition, needs to be inspected further.

Characteristerization of Environment-Friendly Soils Stabilized with Biomass Wood Ash

세계적으로 현재 많은 양의 바이오매스가 농업, 산림 및 에 너지 자원으로 사용되고 있다. 사용된 바이오매스는 단순히 소각되어 바이오매스 재가 되어 일부 재생에너지원으로 재사 용되고 있다. 하지만, 여전히 많은 양의 바이오매스 재가 단순 폐기되고 있는 실정이다. 이는 자원의 낭비와 폐기 공간 부족 등의 문제를 초래하게 되며, 이에 따라 바이오매스 재의 처리 및 활용에 대한 방안은 시급하다고 하겠다. 이 중 나무 및 산 림은 전체 바이오매스 발생량의 약 40%를 차지하며(Fig. 1), 이에 따라 나무재가 바이오매스 재의 많은 비중을 차지하고 있음을 예상할 수 있다. 따라서 나무재를 건설재료로 활용할 수 있다면, 이는 자연자원의 보존과 쓰레기 저감에 크게 기여 할 수 있을 것으로 판단한다. 본 논문은 바이오매스 재의 한 종류인 나무재의 건설재료로 서의 적용 가능성을 타진하기 위하여, 나무재와 나무재가 혼 Abstract

Characteristerization of Biopolymer Solution Used for Soil Remediation and Petroleum Production

Biopolymers are one of environment-friendly materials that can be completely degraded by microbes, not like other chemical prod-ucts. It is more effective to saturate the pore of soils by biopolymer solutions than by water, and therefore biopolymers are used forsoil remediation and petroleum production. Two types of biopolymers, alginic acid sodium salt (SA) and polyethylene oxide (PEO),are employed in this study to experimentally investigate the basic properties – contact angle, surface tension, viscous force – and flowcharacteristics of biopolymer solutions using microfludic device. It was found that the contact angles of biopolymer solutions on a sil-icon dioxide plate were lager than that of water. The magnitudes of surface tensions of biopolymer solutions did not show a cleartrend. The viscous force of biopolymer solutions were larger than that of water, and it increased with increasing concentration of solu-tions. The tests with a microfluidic device showed that the pore is better saturated by the biopolymer solutions with more concen-tration and more injection velocity. The results of this study provides basic properties of biopolymer solutions for flow analysis, andcan be referenced for effective soil remediation and petroleum production usingn biopolymer solutions.Key words : biopolymer, microfluidic device, contact angle, surface tension, viscous force