Soo Sam Kim

Electrokinetic settling and sedimentation behavior of cohesive soils in dilute suspension

In this study, the electrokinetic (EK) effects on settling behavior of clayey soils under different electrolyte solution, electric field strength, and moisture content were evaluated using kaolin and natural marine clay. A number of laboratory-scale column experiment were carried out in order to examine the effects of electrophoresis and electro-osmosis during settling processes. The settling velocity under different electrolyte solution was found to become faster resulting from the formation of floc due to the contraction of electrical double layer. The electrically induced surface settlement was faster in settling rate and greater in magnitude by comparison with that under the conventional gravitational sedimentation. The effects of electrophoresis on settling behavior become significant from the beginning of hindered settling stage due to the influence of electrochemical interactions between the charged clay particles.

Application of enhanced electrokinetic extraction for lead spiked kaolin

In this study, an electrokinetic technique applied for the purpose of extracting lead from contaminated soil was investigated. To do this, the laboratory test for the kaolin clay contaminated by lead was performed and pH distribution, transport of contaminants in soil sample was studied. Moreover, injecting citric acid and SDS solution, anionic surfactant, and the reversal of the electrode were carried out in order to remove accumulated heavy metal in the cathode region. Under 1V/cm voltage gradient, lead was transported to the cathode and the removal rate reduced about at 75% in 80% region between electrodes. In spite of this removal rate, most of the transported lead was precipitated in the cathode region and finally the amount of lead drained into the cathode reservoir was found to be small. However, it was found that injection of citric acid and SDS into the contaminated soil was effective to remove lead three times or more than the unenhanced method.

Soft ground improvements using natural fiber

In this study, natural fiber drains made with coconut coir, rice straw and jute filter were tested to evaluate their practical applicability if used in fields properly. Firstly, the tensile strength, and discharge capacity of the natural fiber drains were tested and verified prior to usage. Based on the test results, natural fiber drains excelled in tensile strength, but their initial discharge capacity obtained from composite discharge capacity tests was less than that of plastic drain board. Although their initial discharge capacity was relatively low compared to that of plastic drain board, the surface settlement from installation of the natural fiber drains, which is one of the most important factors to control the construction progress, was identical to that of plastic drain board. Therefore, it was concluded that the natural fiber drain boards satisfy the required minimum discharge capacity as a vertical drain and have great potential as a substitute for conventional plastic drain board. Secondly, long term changes in tensile strength of natural fiber drains embedded in sea water and clayey soil were examined. The tensile strength of fiber drain board in clayey soils decreased with time. These results indicated active decomposition of natural fibers embedded in sea water and clayey soils.