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

Simulation of dense non-aqueous phase liquid remediation through steam-enhanced extraction

Steam-enhanced extraction has been reviewed by many researchers as an innovative technology to remediate dense non-aqueous phase liquid (DNAPL) from subsurface. However, the application of steam-enhanced extraction to heterogeneous subsurface conditions is still obscurity and its implementation is limited due to steam flow sensitivity to site characterization. Two-dimensional (2-D) simulations were performed to assess the efficiency of steam-enhanced extraction in remediation of heterogeneous subsurface contaminated with tetrachloroethylene (PCE) spill. The simulation was performed with four different steam injection rates. The results shows that increased in steam injection rate will increase the PCE remediation time. The steam injection with the rate of 1.0 x 10-4 kg/s was successfully removing 100% of the PCE. There are significant impacts in the difference in remediation time with the increment approximately 20 min, 40 min and 70 min for every 2.0 x 10-5 kg/s increment. The dominant mechanisms of PCE removal is physical displacement through vaporization and co-boiling enhanced by steam distillation and steam stripping. The simulation results of steam-enhanced extraction for PCE removal was compared with surfactant-enhanced method implemented in existing experimental study. It was discovered that the time required to remove PCE using steam-enhanced extraction is four times faster than the time required to remove PCE using surfactant-enhanced method. This shows the capability of steam-enhanced extraction to recover contaminant more effectively. Steam-enhanced extraction has a greatest potential to decrease clean-up time which will offset greater capitol cost of the system

Awareness of legislation for hand-dug caisson work in highway construction

Hand-dug caisson work is one of the alternative methods of piling for areas that have restrictions on the use of machines. This type of construction work has been used in urban areas in Malaysia. The technique is considered to be a hazardous operation as it involves various high-risk activities, such as lifting and working in confined space. Hand-dug caisson work must comply with various Occupational Safety and Health (OSH) Legislation that covers every aspect of its operation. The aim of this qualitative and quantitative study is to analyze the awareness of highway construction workers concerning legislation that specifically covers hand-dug caisson work. A questionnaire survey was used to determine the awareness of personnel involved in this activity concerning the relevant legislation. Although the results of the survey showed that the personnel were aware of the basic OSH Legislation currently being used in Malaysia, the survey results for specific OSH Legislation related to each process showed that the awareness of the personnel involved was only about 52.44%. The low awareness of OSH Legislation would lead to non-compliance with the Law and impact on the safety, company image, and productivity. Recommendations to improve awareness of the related OSH Legislation are also discussed in this study

Modeling of Petrophysical Relationship of Soil Water Content Estimation at Peat lands

Estimating Soil Water Content (SWC) for peat soil is fundamental parameters that are essential for quality of soil especially during drying periods. Transformations and subsequent losses to groundwater or atmosphere are mediated by moisture conditions in the soil. Success or failure of food, fiber, and energy production from agricultural crops depends on soil water storage between rainfall and/or irrigation events. Despite this importance, predicting soil water dynamics especially during dry and wet season remains a major challenge in hydrology, environmental science, agriculture, and engineering. Hence this study aims to determine the mathematical model for the site-specific of petrophysical relationship for wet and dry season between dielectric permittivity and water content of the peat soil. Field survey measurements and laboratory measurements were conducted at peat soil area. Soil samples were collected from 0 to 1.0m layer for 20 point. Dielectric permittivity values were determined using 2D adjusted of parallel plate capacitor. The oven-drying process was conducted for soil water content estimation. Linear and polynomial models were adjusted for the peat soil between dielectric permittivity and water content. From the results shows that the modeled of site-specific of petrophysical relationship gives better correlation for dry season (R2=0.9812) and wet season (R2=0.9441). The comparisons of GPR-derived estimates of water content to gravimetric measurements showed that GPR measurements using the modeled site-specific petrophysical relationships for both season had a root mean square error of 0.017 (wet season) and 0.25 (dry season). This indicates that the modeled equations can be used to estimate the water content of the peat soil when measured it by using GPR. Besides, through verifying the model of site-specific of petrophysical relationship using ground penetrating radar (GPR) along with three proposed model (Roth equation, Schaap equation and Idi equation) where the season was taken as consideration, the adjusted models provide sufficient accuracy to determine soil water content of peat soil for wet and dry season

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)

Surfactant-alcohol experiments for dense non-aqueous phase liquid removal: a review

The aim of this paper is to review and to summarize the existing laboratory experiment studies from other researchers regarding surfactant alcohol experiment for dense non-aqueous phase liquid (DNAPL) removal, their approach, method of measurement, factor consideration and their findings together with result discussion. This review includes the selection of surfactant-alcohol, their important characteristics in the remediation of DNAPL, the laboratory experimental setup using 2-D laboratory model and enhanced remediation of DNAPL from recent laboratory studies. It has been shown in the laboratory experiment studies that solubilization is the dominant removal process of DNAPL. After surfactant concentration reached the critical micelle concentration, interfacial tension between DNAPL, water and soil decreased. This has resulted in increasing of solubility and removal rate of DNAPL. Mobilization also takes place in the removal process. However, most of the laboratory experiments did not consider other factor such as soil permeability, soil texture, and interfacial tension between soil and DNAPL. Further studies of surfactant-alcohol flushing shall be considered in the near future

Design of oil water separator for the removal of hydrocarbon from stormwater contaminated with jet-fuel

The airport, in general, has a huge catchment area and a hardstand area that includes runways, taxiways, as well as parking aprons. Therefore, these areas are expected to produce a huge volume of stormwater. Besides this problem, the jet fuel and suspended solids contaminate the stormwater flow rate; hence, much consideration should be given in designing the treatment system to ensure that there is no back-flow expected during the high stormwater production to avoid any flooding occurrences in the airports. Currently, the stormwater treatment system in the Malaysian airport is minimal, and there is no specific treatment for the stormwater contaminated with jet fuel in Malaysia. In this paper, an oil-water separator named Corrugated Plate Interceptor (CPI) was explored to treat stormwater contaminated with jet fuel in the airport. Treating the airport stormwater contaminated with oil, grease, or jet fuel could significantly reduce the contamination issue and develop an environmentally friendly airport in Malaysia. The CPI has combs of plates arranged in packs, and this creates the surface areas for the removal reaction of jet fuel and suspended solids between the incoming contaminated stormwater and the plates. Accordingly, in this paper, the design and development of CPI were discussed, particularly on the design criteria for the oil-water separator, standardized tank dimensions, oil storage capacity in the tank, sludge storage capacity in the tank, and finalized plate packs

Design requirements for the treatment of stormwater contaminated with jet fuel oil using corrugated plate interceptor

Oil contamination in the stormwater has been generally overlooked even though it causes major environmental pollution and a substantial threat to all species in the ecosystem. Likewise, the treatment of oil-contaminated stormwater in public areas and general industries, especially airports, has also been ignored. Airports are known as one of the most potent contributors to the jet fuel oil contamination of stormwater that pollutes the local waterways. There are many Best Management Practices (BMPs) of stormwater at airports, such as detention ponds, retention ponds, and infiltration basins in which stored water is exfiltrated through permeable soils. However, not many kinds of literature regarding specific actions taken to treat the stormwater contaminated with jet fuel oil within the boundaries of airport facilities. This paper presents the design requirements for the treatment of stormwater in an airport using corrugated plate interceptor (CPI). Specifically, this paper discusses the characteristics and the contaminants of stormwater runoff from certain airports and the design requirements of CPI in treating the wastewater. The design requirements were based on an actual study conducted in an airport using the CPI. The requirements include determining jet fuel concentration at the inlet and outlet of the CPI; selecting the jet fuel density; evaluating the flow rate, oil storage and sludge storage capacity; and determining the oil globule size and surface charge. In addition, the evaluation of the coefficient of surface separation and the design of corrugated plate packs are also elaborated

Shear strength degradation of Semarang Bawen clay shale due to weathering process

The effect of weathering processes in decreasing the shear strength of clay shale had been done in this study. The drying process of clay shale with sunlight in the laboratory up to 80 days had been conducted to create the conditions of weathered sample. The peak and residual shear strength parameters of unsaturated and saturated clay shale were obtained from triaxial laboratory test, and all samples were tested on each 8 days of weathering process. Decrease of shear strength in peak and residual condition was obtained during 80 days of the drying process. The residual shear strength parameters were distinguished between residual shear strength without stress release and with stress release of confining pressure. The results up to 80 days of unsaturated clay shale showed that the cohesion at peak stress conditions reduced to 30% based on initial shear strength before the occurrence weathering, while the internal angle friction reduced to 64%. Residual cohesion without and with stress release reduced to 4% and 1%, respectively while residual internal angle friction without and with stress release reduced to 15% and 5%. Similar situation also occurs for the saturated clay shale samples

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