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

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 Hydrocarbon Liquids Migration in Double-Porosity Medium Using Digital Image Analysis

The development activity of the country has played a part in natural disasters and climate change such as earthquake, El-Nino, tsunamis and water pollution have caused negative impact on human health and geo-environment. More complicated problems arise when the subsurface has experienced earthquake vibration, which no doubt influences the migration of hydrocarbon liquid into the groundwater sources. These problems need to be addressed in ensuring sustainable groundwater utilization. This paper aims to study the characteristics of hydrocarbon liquid migration that are important for the remediation cleanup of contaminated groundwater. The danger of reproductive toxic hydrocarbon chemicals has made actual on-site study infeasible and has been more practically replaced by physical model simulations. For this purpose, a physical laboratory experimental study was conducted to investigate the pattern and characteristics of different quantity toluene hydrocarbon migration in double-porosity medium under the vibration effect by using digital image analysis. The results of the experiments show that lower quantity of toluene hydrocarbon will take longer time to migrate to the bottom compared to higher quantity of toluene hydrocarbon. During experiment, air bubbles were continuously observed at the soil surface of toluene reducing due to the wettability of the liquids in the soil sample and the air trapped between the fractured aggregate and intra-inter aggregate pores. This study indicate that the digital image analysis is capable to provide the hydrocarbon flow rate and useful information for researchers and professionals to comprehensively understand migration characteristic

Office quality classification theoretical and empirical issues

Office quality classification literature recognises identification of office classes through division of office market rent distribution into intervals but failed to provide sound theoretical framework and comprehensive empirical approach to this method. This paper theorised that as office rental levels are a function of office quality; high quality office classes should have their mean rents greater than average market rent and mean rents of low quality classes. Also that heterogeneous nature of property coupled with lack of perfect information to market participants could result into differential evaluation of rent and quality of the same property by different market participants. The behaviour of participants normally reflects in distribution of market rent by depicting natural breaks in the distribution that could be captured by univariate data exploration. Frequency and histograms of rent distributions that were assumed to depict the behaviour of market participants were used to divide rent distribution to intervals to identify office quality classes. The results of this classification were validated by discriminant analysis. 67% and 59% accuracies were achieved for estimation and holdout subsamples respectively. This paper extended theoretical and empirical approaches in office quality classification. The proposed empirical approach could be used in future classification research

Hydraulic conductivity and volumetric shrinkage properties review on gradation effect of compacted laterite soil liner

This paper reviews the effects of gradation on hydraulic conductivity and volumetric shrinkage properties of compacted laterite soil liner. The distribution of different grain sizes affects the engineering properties of soil such as compressibility, swelling and shrinkage, shear strength, and hydraulic conductivity. It is observed that there are dissimilarities of values in laterite soils from various researches around tropical countries of the world in terms of hydraulic conductivity and volumetric shrinkage. Hydraulic conductivity varies from 4.36×10-3 m/s to 4.7×10-11 m/s and volumetric shrinkage of ≤ 4%relative to fine contents ranging from 1.3% to 69% and coarse contents ranging from 31% to 98.7%.Generally, there is no clear trend established for effects of gradation on hydraulic conductivity and volumetric shrinkage properties of compacted laterite soil liners. This is because laterite soils with less than 50% fines content might not be used as liner or hydraulic barriers because their hydraulic conductivities are less than the minimum requirement of 1 × 10-9 m/s. At times researchers usually left out volumetric shrinkage in their study, but field studies have shown that desiccation can induce severe cracking of unprotected soil barriers. When fine grained soils lose moisture they tend to shrink, which result to cracking that can adversely affect the engineering properties and performance of the soils. The adversative influence includes reduced strength of the cracked soils and increased hydraulic conductivity. It is expected that with logical understanding of the effects of gradation on hydraulic conductivity and volumetric shrinkage properties of compacted laterite soil it will serve as a guide in the design of hydraulic barriers for engineered sanitary landfills in tropical countries around the world

Laboratory and numerical simulations of light nonaqueous phase liquid (LNAPL) in unsaturated zone

The contamination of hydrocarbons in soil and groundwater by fuels and industrial chemicals has become a problem of growing concern. The contaminated groundwater is not only unsafe for human and animal consumption but also not suitable for irrigation purposes. The leaking from underground storage tanks (USTs) and pipelines, hazardous waste sites and surface spills are the general sources of nonaqueous phase liquids (NAPLs). The NAPLs is a common term used in hydrogeology to describe the immiscible, separate liquids phase when in contact with water and/or air that occurred in subsurface environment. These liquids typically have different density and viscosity than water (Charbeneau, 2000). A NAPL with a density less than water is classified as light nonaqueous phase liquid (LNAPL), and a NAPL denser than water is classified as dense nonaqueous phase liquid (DNAPL)

Volumetric shrinkage of compacted soil liner for sustainable waste landfill

One of the main principal sources that contributes to the release of leachates in the environment is the municipal solid waste in landfill facilities. To mitigate the negative effects of leachate, landfill liner is constructed to provide a protective barrier that will not allow the leachate to pass through the compacted soil, which may cause groundwater contamination. Due to seasonal variation in tropical regions, compacted or natural soil liners tend to lose moisture when dry. This result to volumetric shrinkage, which causes cracks that affect the engineering properties and performance of the soils. Groundwater can easily be affected by leachate permeating through these cracks in soils because of desiccation induced by volume change. This paper aims to evaluate the effect of fines content at various gradation and moulding water content on volumetric shrinkage property of compacted laterite soil; and to compare the results with the regulatory standard for compliance to mitigate the negative effects of leachate on the environment. The technique used in this study was to vary the gradation of laterite soil at different moisture contents to achieve a sustainable result. It is observed that the volumetric shrinkage increase as the percentage of fines content increase with corresponding water content. The changes in volumetric shrinkage with time shows a sharp increase within the first five to ten d of drying and then become constant. The soil needs to be compacted on the dry side of optimum moisture content or at the optimum moisture content in order to meet the regulatory criteria of ≤ 4 %

Preliminary inflow and infiltration study of sewerage systems from two residential areas in Kuantan, Pahang / Hiew Thong Yap

Sewerage system is the sole infrastructure which conveys sewage to sewerage treatment plants. The usage of a sewerage system should be optimized at the design stage to enhance environmental protection and human health. Wastewaters flows are produced from domestic sewage whereas inflow and infiltration come from surface runoff and groundwater. The purpose of this study is to identify inflow and infiltration in sewerage systems around Kuantan. This study was conducted in residential catchments at Taman Lepar Hilir Saujana and Bandar Putra with population equivalent of 1253 and 1694, respectively. ISCO 674 Rain Gauge was used to measure rainfall intensity. ISCO 2150 and 4250 Area Velocity Flowmeters were collected wastewater flowrate data which measured at 5-minute intervals and analyzed separately for wet and dry period. Infiltration rate was obtained by comparing the upstream flow and downstream flow from the two selected manholes. Based on the result, the average infiltration rate of Qpeak and Qave was 13.7% and 21.2% higher than the 5% and 10% stated in Hammer and Hammer. Inflow and infiltration is a concern and more comprehensive studies are needed to initiate the review of a revised infiltration rate that is more relevant to the future climate

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

Laboratory simulation of LNAPL spills and remediation in unsaturated porous media using the image analysis technique: a review

Leaking from underground storage and surface spills of hydrocarbon sources can cause serious nonaqueous phase liquid (NAPL) contamination in subsurface environments. The toxic compounds of chemicals have made field study impracticable and it has been replaced by laboratory and numerical simulations. This paper introduces the methodology for two-dimensional light nonaqueous phase liquid (LNAPL) flow behavior and remediation experiments using the image analysis technique (IAT). The LNAPL flow behavior experiments are divided into qualitative and quantitative infiltration and redistribution experiments, with and without numerical modeling. The laboratory setup for the quantitative experiments emphasizes the sand tank fabrication, sand packing techniques, typical porous media properties, and the selection of the LNAPL source. In this paper, several methods of enhanced remediation experiments are discussed to explain how LNAPL extraction was carried out for remediation. The requirements and image processing in the IAT are also highlighted from the existing researches. From the discussion, this nondestructive and nonintrusive technique can provide safer and larger coverage of regions for saturation imaging of LNAPL distribution in porous media compared to other techniques. Overall, this paper discusses the laboratory works to produce a highly reliable saturation imaging and current visualization technique for characterizing and analyzing NAPL migration in 2-D aquifer models