Numerical modelling of thermo-hydromechanical (THM) in deforming porous media for subsurface systems

The study of multiphase flow and heat flow in partially saturated porous media is important in environmental geomechanics engineering because of its relevance to consolidation of porous media in unsaturated zone. A numerical model which describes the thermo-hydro-mechanical (THM) coupled problems in deformable porous material with two-phase flow has been developed. The relationships between capillary pressure, saturation of water and relative permeabilities of water and gas, proposed by Brooks and Corey was used. An extended study of the numerical model, based on the COMES-GEO code was conducted recently to solve unsaturated problems in local condition of Kg. Puteh wellfield, Kota Bharu. This site is a potential shallow aquifer which contribute to the largest groundwater supply in Kota Bharu, Kelantan. Some numerical investigation on the proposed formulation is discussed with illustrative example problems to demonstrate solution procedures and validating of the model

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 doubleporosity 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 the Influence of Particle Size on the Migration of DNAPL in Unsaturated Sand

Four experimentswere conducted to investigate the migration of dense non-aqueous phase liquid (DNAPL) in unsaturated porous media using Light Reflection Method (LRM). The porous media was natural sand collected from a river and segregated into different sizes through sieving. Three different sizes of the sand were used in the first three experimentswhile the fourth experiment used a mixture of these sands.The sands were packed separately in rectangular acrylic columns and then DNAPL was injected from the top of the column. The migration of DNAPL, modeled by tetrachloroethylene (PCE), 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 into the software. The results show a significant difference in the migration of PCE through these sands. The migration of PCE in Experiment 3 was much faster than the migration in the other experiments. This is most likely due to the large pores in the sand samples. Moreover, in the experiment using mixture sand, it was observed that the migration was uneven and relatively slower than other experiments. LRM provides a non-intrusive and non-destructive tool for studying fluid flow for which rapid changes in fluid flow in the entire flow domain is difficult to measure using conventional techniques

A Review of Light Reflection and Transmission Methods in Monitoring Non-Aqueous Phase Liquid Migration in Porous Media

Recently, image analysis techniques in monitoring non-aqueous phase liquid (NAPL) migration have been gaining attention from researchers. Over the last two decades, photographic methods such as light reflection and light transmission methods have been shown to be applicable and effective tools for characterization and measuring NAPL migration. A review of recent studies published on light reflection and light transmission methods used in NAPL migration is summarized and presented in this paper. Besides discussion on the research efforts, recommendations for future research in using light reflection and light transmission methods are provided. This study concluded that, although having some limitations and drawbacks, photographic methods are still a promising and valuable tool for measuring NAPL migration

Application of Light Reflection Method to Observe DNAPL Movement in Different Soil Media

In this research, the behaviour of dense non-aqueous phase liquid (DNAPL) was observed in different unsaturated porous media using light reflection method (LRM). Natural sand was used as a porous media that was collected from a river and segregated into different sizes through sieving. Three different sizes of the sand were used in this study. The sands were packed separately in rectangular acrylic columns and then DNAPL was injected from the top of the column. Tetrachloroethylene (PCE) was used as the DNAPL, and it was observed using a digital camera connected to a laptop and controlled using special software. The findings show a significant difference in the migration of PCE through these sands. The migration of PCE in Experiment 3 was much faster than the migration in the other experiments. This is most likely due to the large pores in the sand samples. LRM provides a non-intrusive and nondestructive tool for studying fluid flow for which rapid changes in fluid flow in the entire flow domain is difficult to measure using conventional techniques

An Overview of Photographic Methods in Monitoring Non-Aqueous Phase Liquid Migration in Porous Medium

Over the last decades and among numerous techniques, image analysis techniques occupy a noticeable place in monitoring non-aqueous phase liquid (NAPL) migration in porous media. In recent years, photographic methods have been shown to be valuable and effective tools for measuring NAPL migration and characterization. This study aims to provide an overview of NAPL fate and behavior in subsurface systems. Furthermore, a review of recent literature published on using photographic methods in NAPL migration in one and two dimensions is summarized and presented in this paper. Besides the discussion of the research efforts, recommendations for future research in using photographic methods are provided. This study concluded that, although photographic methods have some limitations and drawbacks,photographic methods are still promising and valuable tools for measuring NAPL migration

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

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 top-soils, 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 contaminants 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 by using the second approach. In conclusion, the LTV method is viable to monitor the behavior of fluids in porous media under different conditions

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

A review of meteorological drought based indices towards integrated water resources management in Iraq

Drought is considered as one of the natural dangerous and extreme phenomena. Since ancient times, the world had suffered from drought, which has a negative impact on human life that affect economic, social, cultural and tourism sectors. It means a severe shortage of water resources due to lack of rainfall and falling below the normal rate during a certain period of time, causing heavy losses on agricultural production, forcing some population to migrate and occurrence of disasters humanitarian disasters such as famine. Climate in Iraq is classified as a semi-arid and arid, many researchers had found that Iraq has suffered from drought, but this suffering will increase in the future due to deficiency of expected precipitation and increase temperatures. Therefore, the aimed to review meteorological drought in Iraq. This paper attempts to illustrate the key elements, indices, and categorization of drought and previous studies conducted in Iraq about drought. Conclusions of the review highlight gaps where it needs to focus more research of integrated water resources management to be implemented by decision makers in Iraq