Double-porosity Soil Research Articles

Predicting the soil freezing characteristic curve of the expansive soil with double porosity accounting for hydraulic effects

Based on the similarity between the drying-wetting process and freezing-thawing process in the soil, a physically based equation predicting the soil freezing characteristic curve (SFCC) can be formulated combining the generalized Clapeyron equation. In this paper, by introducing the weighing factors in two scales of pore sizes, the physically based equation for single-porosity soil is extended for double-porosity soil, with the ability in well characterizing the bimodality of the SFCC. A systematic approach formulating the SFCC of the expansive soil is presented accounting for the pore size distribution and its evolution in two scenarios of the hydraulic conditions. Good agreements can be found between model predictions and experimental data for both scenarios. The effects of hydraulic condition on the pore structure of an expansive soil, as well as the consequences of the evolved pore structure on the SFCC, are emphasized and quantified. In addition, the framework presented herein demonstrates how an initially bimodal SFCC evolves into a unimodal shape along hydration and provides the theoretical SFCCs at different levels of saturation, which contributes to modelling the water-heat transfer in the freezing process of the unsaturated expansive soil.

Investigation of light non-aqueous phase liquid penetration in double-porosity using physical experiment and computer simulation

Groundwater resources benefits to human activity for developing country. Groundwater contamination is crucial, particularly due to the amount of leakage and spillage of hydrocarbon liquids such as light non-aqueous phase liquids (LNAPLs), resulting in contaminated the groundwater and unsafe for domestic and agriculture activities. Penetration of hydrocarbon liquids into groundwater can be seen through double-porosity soil. Therefore, this paper investigates the penetration of LNAPLs in double-porosity soil using computer modelling to calibrate and validate from physical experiment data. These computer modelling and physical experiment studies discuss the pattern and rate of LNAPL penetrations by employing PetraSim commercial software and digital image processing technique (DIPT) by using acrylic glass cylinder, mirror and Nikon D90 digital camera. The LNAPL volume of 70 ml and 150 ml were poured instantaneously onto the surface of soil sample for calibration and validation purposes. The penetration pattern in double-porosity were monitored and recorded using digital camera at pre-determine time intervals. The images were processed using Surfer software and Matlab routine to plot the LNAPL penetration pattern. PetraSim simulation was used to calibrate and validate the penetration of LNAPL through double-porosity soil with physical experiment data. As a result, the PetraSim results valid with the physical experiment results. The Nash-Sutcliffe efficiency results more than 0.50 with percentage of differences for calibration and validation are 1.34% and 5.47% between physical experiment and PetraSim simulation. As a conclusion, PetraSim simulation can be used for further investigation on LNAPL penetration through subsurface soil.

Experimental investigation of cosolvent flushing of DNAPL in double-porosity soil using light transmission visualization

This paper investigates the effect of cosolvent content and flushing velocity on the remediation of dense non-aqueous phase liquid (DNAPL) in double-porosity medium using light transmission visualization technique (LTV). Double-porosity was created using local silica sand and sintered spheres of kaolin, arranged in a periodic manner. The flushing solution consisted of ethanol–water mixtures with various ethanol concentrations ranging from 20% to 65% by volume. The effect of contact time was investigated by changing the flow rates of the flushing solution. The accuracy of the LTV technique was examined by comparing an actual injected volume of DNAPL with the calculated volumes generated from image analysis. The LTV results allowed for the visualization of the DNAPL enhanced dissolution as well as its mobilization. While the removal efficiency increased with the increase of the ethanol content, the removal efficiency was negatively affected by the velocity of flushing solution. Image analysis revealed that the highest DNAPL removal efficiency of 92% was obtained at 65% ethanol content and low flushing velocity. This efficiency decreased to 85%, in the case of high flushing velocity. Overall, this study demonstrated that the LTV technique is a viable laboratory tool that can accurately depict enhanced DNAPL dissolution and DNAPL mobilization due to cosolvent flushing.

Characterization of Capillary Pressure–Saturation Relationships for Double-Porosity Medium Using Light Transmission Visualization Technique

Capillary pressure saturation (Pc–Sw) relationship plays a central role in the description of fluid flow in porous media. In this research, the light transmission visualization (LTV) technique was applied to characterize the Pc–Sw relationship in a double-porosity medium. Four experiments were conducted in two-dimensional (2-D) flow chambers packed with a double-porosity medium composed of a mixture of silica sand and sintered kaolin clay spheres. In each experiment, a different volumetric fraction of macropores and micropores was used. The experiment was also repeated by compacting the flow chamber with silica sand only to represent single-porosity medium. Variable saturations of water across the height of the system were applied by controlling the capillary pressure. Images of the 2-D model were collected using a digital camera and analyzed pixel by pixel to determine water saturation in the double-porosity medium. Results from the LTV technique showed that the Pc–Sw relationships for all experiments in double-porosity soil medium were similar in shape but varied depending on the porous media composition. Comparison with the pressure cell test results showed that the Pc–Sw curves for all experiments consistent comparable to those obtained by the LTV technique. The Pc–Sw curves were also fit to van Genuchten model for comparison and validation. For double-porosity media, the best-fit parameters were consistent with published data for sandy clay. Moreover, little variability was observed in the best-fit α and n values for the different double porosity. Overall, this study proves that the LTV technique is a noninvasive laboratory tool that can provide high-resolution spatial data for water saturation distribution in different types of porous media and is capable of producing highly resolved Pc–Sw relationships.

Consolidation behaviour of double-porosity clay using flexible wall permeameter

Restoration of a site that has previously been prepared using dredged clay is a serious geotechnical challenge. Much of these clays exists as lumps suspended in slurry. These double-porosity soils consolidate due to the expulsion of water from the voids within each lump and the voids between the lumps. Due to this complex nature, the conventional theory of consolidation is not applicable to them. This study discusses the laboratory consolidation test results of double porosity samples. The tests were conducted on 10–30 mm clay lumps. The size, initial packing and the stiffness of the lumps were the variables. At low confining pressure the 30 mm lumpy samples experienced a significantly higher deformation than the 10 mm lumpy samples. In all the tests, the lumps and slurry merged to close the inter-lump voids as confining pressure neared or reached the pre-consolidation lump pressure. This paper also discusses the use of a simple constitutive relationship to model the behaviour of double-porosity fill. It uses the structured clay framework to describe the volumetric strain in the double-porosity samples by using two parameters, in addition to those required in the critical state soil mechanics. A parametric study demonstrated the capabilities of this model.

Vibration impact towards deformable laterite soil with different moisture content

In engineering practice, natural and man-made vibration phenomenon can cause dynamic stress to be imposed on soils such as blasting, construction operations and machinery, and vehicle traffic vibrations. This issue need to be addressed to ensure the geo-environment is sustainably secure. Laboratory experiments were conducted to characterize the behaviour of vibrated deformable double-porosity under different moisture content in repeated vibration. This paper presents the investigation of vibrated double-porosity soil by aggregating laterite soil with 29%, 32% and 34% moisture content. The experiments were conducted by using acrylic soil column, accelerometer and vibrating table. Aggregated laterite soil is poured in acrylic soil column then compress until 10 cm height. High-frequency accelerometers were installed to observe acceleration at 2 points; (1) surface of soil sample, and (2) surface of vibrating table. The experiments for repeated vibration were conducted by increasing the amplitude of the vibrating table. The acceleration time histories at accelerometers were collected to observe maximum amplitude. The results showed that the acceleration response in non repeated vibration was increased with increasing of moisture contents. It was found that with vibrated samples, the soil structure was rearrange and porosity characteristics identified as expected influence the speed of liquid penetration.

Impact of Vibration on Double-Porosity Unsaturated Laterite Soil with Different Water Contents

Engineering practices, natural and man-made vibrations phenomena such as blasting, construction machinery and operations, and vehicle traffic vibrations can cause stresses to soils. In addition, changes in moisture content may affect the speed of liquid penetrating the soils. Therefore, the impacts due to vibrations and changes in moisture contents need to be addressed to ensure geo-environment sustainability. This can be achieved by conducting laboratory experiments to determine the behaviour of deformable double-porosity soil samples with different water contents subjected to non-repeated vibrations. In this study, aggregated laterite soil samples were prepared with 30% and 34% moisture contents. Each aggregated soil was poured into an acrylic column then the soil was compressed to a pre-determined height of 10 cm. Testing was performed on each soil column using a vibrating table where accelerometers were installed to measure high-frequency acceleration time histories on the surfaces of the vibrating table and laterite soil. The tests were conducted by increasing the amplitude of displacement and the acceleration time histories were collected to record maximum amplitudes. The results showed that the soil surface acceleration in non-repeated vibration was increased with increasing moisture contents. It was also discovered that the speed of liquid penetration was influenced by vibration due to rearrangement of soil particles and changes in soil structure and porosity characteristics.

Assessing the influence of infiltration on the migration of light non-aqueous phase liquid in double-porosity soil media using a light transmission visualization method

The influence of infiltration on the migration of a light non-aqueous phase liquid (LNAPL) in double-porosity soil using the light transmission visualization (LTV) technique is investigated. Two LNAPL volumes (low and high volumes) were exposed to two rainfall intensities (light and heavy infiltration). For comparison purposes, the experiments were also repeated by compacting the flow chamber with silica sand only to represent the single-porosity medium and to investigate the influence of double-porosity on LNAPL migration. High-resolution LTV images of the flow chamber during LNAPL injection and subsequent water infiltration events were collected. Results show that the LNAPL migration depth during injection and its migration velocity were both correlated to the LNAPL volume. Subsequent water infiltration events caused the LNAPL that was entrapped in the porous media to be pushed further downward in all the experiments. The LNAPL migration velocity was 1.1 and 1.6 cm/h for the low and high LNAPL spillage volumes for double-porosity experiments, respectively, a reduction rate of 64.7 and 70% compared to the LNAPL migration velocity during LNAPL injection, respectively. However, for single-porosity experiments, the LNAPL migration velocity was 0.7 and 1.2 cm/h for the low and high LNAPL volumes, respectively. Furthermore, it was observed that the capillary fringe level was depressed in the saturated zone due to the influence of both infiltration and LNAPL volume. This study demonstrates that the LTV technique is an accurate and cost-effective laboratory tool for the visualization of the time-dependent influence of infiltration on LNAPL migration in porous media.

Vibration effect influence upon non-aqueous phase liquid migration in double-porosity soil

Natural disasters such as earthquakes, El-Nino, tsunamis and water pollution have a negative impact on human health and living environment. Some of these may give rise to subsurface vibrations that can potentially increase groundwater pollution risks in double-porosity systems. The more complicated situation was where underground storage tanks and petroleum pipeline damage have caused the leakage of non-aqueous phase liquids (NAPLs) which migrated into the groundwater resources. These problems need to be addressed by both professionals and researchers worldwide to ensure the sustainability of groundwater utilization. This paper aims to investigate and understand NAPL migration in vibrated double-porosity soils. To do so it was necessary to study the phenomena and characteristic of soil structure and the pattern of NAPL migration to identify cost-effective remediation schemes. A laboratory experiment was conducted to study the phenomena and characteristics of vibration response and NAPL migration in double-porosity soil deformation under vibration effect using a digital image processing technique(DIPT). The outcomes of the experiment show that the gradual increase of vibration table excitation frequency yielded different vibration responses from the respective soils. This indicated that soil surface acceleration depended significantly on the soil conditions, soil water content, soil structure and the pattern of soil fracturing. NAPL migration was faster in sample 2 with 150 ml toluene than sample 1 with 70 ml toluene and this could be because the greater amount of toluene in sample 2 exerted an extra entry force on top of the soil sample that had yet to migrate through the sample surface. Finally, it was concluded that the DIPT may provide detailed information, and can be used to understand and identify the remediation method as well as to ensure the sustainable consumption of groundwater.

Laboratory Investigation of LNAPL Migration in Double-Porosity Soil Under Fractured Condition Using Digital Image Analysis

The issue of leakage and spillage of light non-aqueous phase liquid (LNAPL) contribute to groundwater contamination, resulting in groundwater pollution and rendering the quality of groundwater unsafe for drinking and agriculture. Therefore, the objective of this study was to investigate LNAPL migration in the double-porosity soil under vibration effect, which has become important for sustainability of groundwater utilization and a comprehensive understanding of the behaviour of liquid migration into the groundwater. A laboratory experiment was conducted to observe the phenomena and characteristics of soil structure, and the pattern of liquid migration in deformable double-porosity by using digital image processing technique. The experiments show that the simulated results were reasonably concise with the visual observations. The gradual increase in vibration table excitation frequency yielded different vibration responses from the respective soils. This indicated that the soil surface acceleration depended significantly on the soil conditions, soil water content, soil structure, and the pattern of soil crack. Faster migration occurred at the cracked soil surface condition compared to other locations on the soil surface that were not cracked. Comparison between soils with 25% and 30% moisture content showed that the downward migration of LNAPL is faster when the soil moisture content is higher. This occurs in soil with higher moisture content due to greater capillary pressure exerted by the liquids and the inter-aggregate pores. This study proved that the digital image processing technique is capable to provide detailed migration flow information to facilitate the researchers to better understand contaminate migration patterns and to ensure sustainability of groundwater resources.

Study of Aqueous and Non-Aqueous Phase Liquid in Fractured Double-Porosity Soil Using Digital Image Processing

The leakage and spillage of non-aqueous phase liquids (NAPLs) and aqueous phase liquids (APLs) contribute to groundwater contamination, resulting in groundwater pollution and rendering the quality of groundwater unsafe for drinking and agriculture. Ensuring the availability and sustainable management of water and sanitation for all was the goal and target of the 2030 United Nations agenda for sustainable development, consisting of a plan of action for the population, the planet and general prosperity. This paper is intended to investigate the aqueous and non-aqueous phase liquid migrations in a deformable double-porosity soil, which has become important for both sustainable groundwater use and the comprehensive understanding of the behaviour of liquid migration into groundwater. A modelling experiment was conducted in an attempt to study the pattern and behaviour of aqueous and non-aqueous phase liquid migration in fractured double-porosity soil using a digital image processing technique. The results of the experiments show that the flow of the APL and NAPL migration was not uniformly downward. Faster migration occurred where the soil surface was cracked compared to other locations where the soil surface was not cracked, even when liquids such as toluene were not used. It was concluded that the factors that significantly influenced the APL and NAPL migration were the structure of the soil sample, fracture pattern of the soil sample, physical interaction i.e. bonding between the liquid and soil sample, and the capillary pressure of the fluid. This study indicates that digital image analysis can provide detailed information to help researchers better understand and be able to simulate the pattern and characteristics of liquid migration that have an influence on groundwater resources.

Investigation of aqueous and non-aqueous phase liquid migration in double-porosity soil using digital image analysis

The development activity of the country has played a part in climate change and natural disasters, which lead to a negative influence on the geo-environment and health. The issues of leakage and spillage of Non- Aqueous Phase Liquids (NAPLs) and Aqueous Phase Liquids (APLs) contribute to groundwater contamination, resulting in groundwater pollution and rendering the quality of groundwater unsafe for drinking and agriculture. Ensuring availability and sustainable management of water and sanitation for all were the goal and target of the 2030 United Nations agenda for sustainable development, consisting of a plan of action for people, planet and prosperity. This paper investigates the aqueous and non-aqueous phase liquid migrations in the deformable double-porosity soil, which has become important for sustainability of groundwater utilisation and a comprehensive understanding of the behaviour of liquid migration into the groundwater. An experiment model was conducted to study the pattern and behaviour of aqueous and non-aqueous phase liquid migration in deformable double-porosity soil using digital image processing technique. The results of the experiments show that the flow of the APL and NAPL migration was not uniformly downward. Faster migration occurs at the cracked soil surface condition compared to other locations on the soil surface that were not cracked, even when not using liquid such as toluene. The factors that significantly influence the APL and NAPL migration are the structure of the soil sample, fracture pattern of the soil sample, physical interaction bonding between the liquid and soil sample, and the capillary pressure of the fluid. This study indicates that digital image analysis provides detailed information to facilitate researchers to better understand and simulate the pattern of liquids migration characteristics as well as to ensure sustainable consumption of groundwater.

Non-aqueous phase liquids distribution in three-fluid phase systems in double-porosity soil media: Experimental investigation using image analysis

Over the last few decades, contamination of groundwater and soil by non-aqueous phase liquids (NAPLs) has become a serious and wide-spread problem for the environment In this research, a light transmission visualization (LTV) method was used to observe the migration of dense non-aqueous phase liquid (DNAPL) and light non-aqueous phase liquid (LNAPL) in double-porosity soil within a three-fluid phase system (air-NAPL-water). The double-porosity characteristics of the soil were created using a composition made up of local sand and sintered kaolin clay spheres arranged in a periodic manner. Toluene was used to simulate LNAPL while tetrachloroethylene (PCE) represented the DNAPL. Both NAPLs were dyed using Oil-Red-O for better visualization. For comparison purposes, the same experiments were carried out using just local silica sand acting as a type of single-porosity soil. A significant difference in the migration of the toluene and PCE was observed as both the NAPL migration rates in the double-porosity medium were much faster compared to the migration rates found in the single-porosity medium. This result is most likely due to the occurrence of inter-aggregate pores in the double-porosity soil that contribute to increasing velocity of fluids migration through porous media. Other factors such as the wettability of fluids and capillary pressure characteristics that exist in the soil pores were found to be influential factors in fluid migration within porous media. In addition, the results show that chemical properties have a significant influence on the NAPL migration in porous media. It was found that the migration velocity of toluene was much faster compared to the migration velocity of the PCE. This observation is most likely caused by the fact that the distribution coefficient of toluene was higher than that of PCE which in turn means that the retardation factor of toluene is lower than that of PCE in the same porous media. This paper proved that the LTV provides a non-intrusive and non-destructive technique for studying multiphase flow in double-porosity soil media where rapid changes in fluid distribution in the entire flow domain is not easy to measure using conventional tools.

Experimental study on aqueous phase liquids migration in double-porosity soil under non-isothermal effect using digital image analysis

Aqueous phase liquid (APLs) leakage and spillage into the subsurface system, leading to groundwater contamination is an issue that needs to be addressed. This paper aims to investigate the APLs migration characteristics in fractured non-isothermal double-porosity soil. A laboratory experiment was conducted to observe and monitor the characteristics of the soil structure and APLs migration in heated deformable double-porosity soil using digital image processing technique. The results show rapid liquid migration for the fractured soil samples. The time taken for the liquid to migrate under the application of heat is less for sample with low moisture content due to faster dry off and rapid evaporation. It can be concluded that APLs migration under vibration and non-isothermal effect is highly influenced by the soil sample structure, the soil fractured pattern, the soil water content, and the applied heat in the soil.

Investigation of Aqueous and Non-Aqueous Phase Liquids Migration in Fractured Double-Porosity Soil

The issue of leakage from underground storage tank and spillage of contaminate liquids can contribute to the aqueous and non-aqueous phase liquids contamination into the groundwater, resulting in groundwater pollution and rendering the quality of groundwater unsafe for consumption. Ensuring availability and sustainable management of water and sanitation for all was the goal and target in the 2030 agenda for sustainable development, consisting of a plan of action for people, planet and prosperity of the United Nations. This paper is intended to investigate the aqueous and non-aqueous phase liquid migrations in the fractured double-porosity soil, which become important for sustainability of groundwater utilisation and a comprehensive understanding of the pattern and behaviour of liquid migration into the groundwater. For this aim, an experiment model was conducted to study the pattern and behaviour of aqueous and non-aqueous phase liquid migration in fractured double-porosity soil using digital image processing technique. Outcome of the experiments show that the fractured double-porosity soil has faster liquid migration at the cracked soil surface condition compared to intact soil surface. It can concluded that the factors that significantly influence the aqueous and non-aqueous phase liquids migration was the soil sample structure, soil sample fractured pattern, physical interaction bonding between the liquid and soil, and the fluid capillary pressure. This study demonstrates that the hue saturation intensity contour plot of liquids migration behaviour can provide detailed information to facilitate researchers and engineers to better understand and simulate the pattern of liquids migration characteristics that influence the groundwater resources .

EXPERIMENTAL STUDY ON UNSATURATED DOUBLE-POROSITY SOIL PHENOMENA UNDER VIBRATION EFFECT

A physical experiment approach was conducted to observe the deformation of double-porosity soil under vibration effect. The double-porosity soil characteristic was created using kaolin soil. An experiment on a soil sample fitted with accelerometer was conducted on a vibratory table to obtain peak ground acceleration and peak surface acceleration. After the vibration process, the deformable double-porosity soil was verified through field emission scanning electron microscopy tests. As seen in the microscope images, large surface cracks were observed due to the weakness of aggregated kaolin soil structure with its 25% water content. However, the 30% water content soil had small surface cracks due to its stronger soil structure. It was found that the deformable double-porosity soil had more fractured pores compared to the intact soil sample. From the acceleration response analysis, it was seen that both samples had amplification and dis-amplification shaking. In conclusion, the fractured double-porosity, as expected, has high permeability become a dominant factor in fluid migration. Meanwhile, the unconstrained soil and large fracture structure fabric showed significantly different porosity. The percentage of water content plays an important role in the structure of fractured double-porosity soil.

Influence of Macro-pores on DNAPL Migration in Double-Porosity Soil Using Light Transmission Visualization Method

Double porosity is a substantial microstructure characteristic in a wide range of geomaterials. It is a natural phenomenon that can be found in many types of soil, and it can result from biological, chemical or mechanical damage. In this paper, the influence of macro-pores on dense non-aqueous phase liquid (DNAPL) migration in double-porosity medium was investigated using light transmission visualization technique. Three experiments were carried out in two-dimensional flow chambers filled with a double-porosity medium composed of a mixture of local sand and sintered kaolin clay spheres arranged in a periodic manner. In each experiment, a different volumetric fraction of macro-pores and micropores was used. Tetrachloroethylene (PCE) was used to simulate DNAPL, and it was dyed using Oil-Red-O for better visualization. A predetermined amount of PCE was injected into the flow chambers and this amount was re-calculated using image analysis. A very strong correlation was found between the PCE amount injected and the amount calculated from image analysis in each experiment. The experiment was repeated by filling the flow chamber with silica sand to represent single-porosity medium. The results show that the macro-pores have a considerable effect on the PCE migration in double-porosity soil as the PCE movement was the fastest in the third experiment which contained the largest macro-pores volume. The accuracy of the method was validated using statistical analysis. The results show a slight difference between the means of the three experiments, indicating that the method is viable for monitoring NAPL migration in double-porosity medium under different volumetric fractions of macro-pores and micropores.

QUANTIFICATION OF DENSE NONAQUEOUS PHASE LIQUID SATURATION IN DOUBLE-POROSITY SOIL MEDIA USING A LIGHT TRANSMISSION VISUALIZATION TECHNIQUE

In this research, the light transmission visualization (LTV) technique was used to measure the dense nonaqueous phase liquid (DNAPL) saturation distribution in a two-dimensional (2-D) flow chamber packed with double-porosity soil medium. This, to the best of our knowledge, is a new application of LTV in measuring DNAPL saturation as well as monitoring its migration in double-porosity soil media. The double-porosity structure was created using layers of fine silica sand and solidified kaolin clay spheres. Tetrachloroethylene (PCE) was used to simulate DNAPL and was dyed with Oil-Red-O for better visualization. Known amounts of PCE were injected into the flow chamber before being correlated to amounts calculated using image analysis based on the LTV method. A strong correlation having an R2 value of 0.994 was found between the injected PCE volumes and calculated PCE volumes obtained from the LTV method. For comparative purposes, the same experiment was carried out by filling the flow chamber with local silica sand as a single-porosity medium to investigate the influence of soil structure on DNAPL migration. Results, again, showed a strong correlation, with an R2 value of 0.996, between the amounts of PCE injected into the flow chamber and the calculated amounts of PCE. A significant difference in the migration of PCE in the two experiments was observed as the rate of PCE migration in the double-porosity medium was much faster compared to the migration rate in the single-porosity medium. This finding is most likely due to the occurrence of interaggregate pores in the double-porosity soil. This research proves that the noninvasive and nonintrusive LTV technique can be used to quantify DNAPL saturation in double-porosity soil structure in 2-D, two-phase systems.

Assessment of the behaviour of soil structure in double-porosity kaolin media using light transmission visualization (LTV) method

Double-porosity is a phenomenon that occurs naturally and can be found in many subsurface media such as rock aquifers, agricultural topsoils and compacted soils. These media have different pore size characteristics that result in different hydraulic properties. Two approaches were used to create the double-porosity soil structure using kaolin clay to be tested in migration of contaminant experiments using light transmission visualization (LTV) method. Aggregated kaolin and sintered clayey spheres mixture were used as the media for the first and second test, respectively. The observation shows that the first approach is not viable for a saturated-porous medium because kaolin particles have disintegrated and turned into emulsion. In contrast, uniform kaolin particles that remain strong and solid have been produced using the second approach. In conclusion, the LTV method is viable to monitor the behaviour of fluids in porous media under different conditions.

Investigation of Light Non-Aqueous Phase Liquid Migration Single and Double-Porosity Soil Using Light Transmission Visualization Method (LTV)

Two experiments were conducted to investigate the migration of light non-aqueous phase liquid (LNAPL) in two different porous media using LTV technique. The first media was fine sand as a single-porosity and the second media was S300 kaolin as a double-porosity. The two media were packed separately in the flow chamber and then LNAPL was injected from the top of the model and the migration of LNAPL (Toluene) was observed using a digital camera connected to a laptop and controlled using special software. The images were captured according to a predetermined time interval set by the software. The results show a significant difference in the migration of LNAPL in the two porous media, where the migration in the double-porosity media was much faster than the migration in the single-porosity. This finding is due to the occurrence of inter-aggregate pores in the double-porosity soil structure. This paper shows that more attention should be given towards the pollution of the groundwater sources that are located within or near the double-porosity media especially the agricultural soil.