Simulation on the Permeability Evaluation of a Hybrid Liner for the Prevention of Contaminant Diffusion in Soils Contaminated with Total Petroleum Hydrocarbon

Abstract

This study describes the test results to evaluate the impermeability efficiency, according to the total petroleum hydrocarbon (TPH) reaction time of a hybrid liner for preventing the TPH diffusion, and the numerical analysis results, according to the various TPH reaction times of the hybrid liner. The experimental results indicated that the hybrid liner performed effectively as an impermeable material under the condition of a 4 h reaction time between TPH and the hybrid liner. In other words, the permeability of the hybrid liner was lower than 7.64 × 10^-7 cm/s when the reaction time of the TPH and the hybrid liner exceeded 4 h. This means that polynorbornene applied as a reactant becomes completely gelated four hours after it reacts with TPH, demonstrating its applicability as a liner. The numerical analysis results to evaluate the TPH diffusion, according to the hybrid liner-TPH reaction time indicated that the concentration decreased, compared to the initial concentration as the hybrid liner-TPH reaction time increased, regardless of the head-difference and the observation point for all concentration conditions. In addition, the reduction ratio of the concentration, compared to the initial concentration was 99% ~ 100%, when the reaction time of the hybrid liner-TPH was more than 4 h. It was found that the concentration diffusion of TPH reacting with the hybrid liner was decreased when the distance from the hybrid liner and the reaction time of the hybrid liner-TPH were increased. In other words, in the case of a high-TPH condition, the concentration reduction ratio is 12.5~17.8%, 16.9~29.7%, depending on the distance ratio (D/L = 0.06, 0.54, 0.94), respectively, when the reaction time of the hybrid liner-TPH is 0 h and 0.5 h, respectively. In the case of medium- and low-TPH conditions, the concentration reduction ratio, according to the distance ratio is 12.0% to 20.8% and 17.0% to 29.8%, respectively. This result means that a numerical analysis model can be used sufficiently to predict the TPH diffusion, according to the distance from the location where the hybrid liner is installed.

Keywords: contaminant; diffusion; hybrid liner; permeability.

Figure 1

Hybrid liner: (a) Conceptualization; (b) Gelation over time (modified from [32]).

Figure 1

Hybrid liner: (a) Conceptualization; (b) Gelation over time (modified from [32]).

Figure 2

Absorption, expansion, and gelation of polynorbornene (reactive material): (a) Weight change after the reaction with TPH, before: 3.5 g, after: 130.1 g; (b) Gelation over time [32].

Figure 3

Permeability test apparatus: (a) Schematic; (b) Set-up.

Figure 4

FDA model: (a) 3D view; (b) Plan view (modified from [32]).

Figure 5

Variation of the permeability coefficient of the hybrid liner by reactive time of TPH.

Figure 6

Concentration variance at the high-TPH condition: (a) Maximum concentration (ppm) at the observation point; (b) Reduction ratio of the concentration at the observation point.

Figure 6

Concentration variance at the high-TPH condition: (a) Maximum concentration (ppm) at the observation point; (b) Reduction ratio of the concentration at the observation point.

Figure 7

Concentration variance at the medium-TPH condition: (a) Maximum concentration (ppm) at the observation point; (b) Reduction ratio of the concentration at the observation point.

Figure 7

Concentration variance at the medium-TPH condition: (a) Maximum concentration (ppm) at the observation point; (b) Reduction ratio of the concentration at the observation point.

Figure 8

Concentration variance at the low-TPH condition: (a) Maximum concentration (ppm) at the observation point; (b) Reduction ratio of the concentration at the observation point.

Figure 8

Concentration variance at the low-TPH condition: (a) Maximum concentration (ppm) at the observation point; (b) Reduction ratio of the concentration at the observation point.

Figure 9

Evaluation of the impermeable efficiency using D/L: (a) High-TPH condition (6000 ppm); (b) Medium-TPH condition (2000 ppm); (c) Low-TPH condition (500 ppm).

Figure 9

Evaluation of the impermeable efficiency using D/L: (a) High-TPH condition (6000 ppm); (b) Medium-TPH condition (2000 ppm); (c) Low-TPH condition (500 ppm).