Cover System Design Research Articles

Theoretical Analysis of Landfill Gas Migration in Capillary Barrier Covers Considering Effects of Waste Temperature

The high-temperature and high-humidity conditions arising from the biochemical degradation of landfill waste result in significant temperature gradients within the landfill cover. The effects of waste temperature on landfill gas transport and microbial aerobic methane oxidation are not fully understood. In this study, a fully coupled theoretical model was developed to simulate the interactions of moisture, heat, and gas transport within a capillary barrier cover. A series of parametric studies were carried out to investigate the influence of the combined effects of temperature gradient, initial soil moisture content, and landfill gas generation rate on methane transport, oxidation, and emissions. The simulated results indicated that increasing waste temperature intensified the temperature gradient, leading to higher surface evaporation rates and variations in methane oxidation efficiencies. Additionally, variations in initial soil moisture content and landfill gas generation rates were found to significantly impact gas migration and methane oxidation in the cover. This study demonstrates the critical role of waste temperature in landfill gas migration within landfill cover systems, providing technical methodologies for the optimized design of soil cover systems.

Short-Term Predictions of Evaporation Using SoilCover at the Near-Surface of a Mine Waste Pile following Heavy Rainfall Events

Accurate measurements and predictions of near-surface soil drying and evaporation following heavy rainfall events are often needed for research in agriculture and hydrology. However, such measurements and predictions at mine waste pile and tailing settings are limited. The prediction of evaporation at mine waste piles is essential for many problems in geotechnical engineering, including the design of soil cover systems for the long-term closure of hazardous waste sites, and thus mitigates, for example, the generation of acid mine drainage (AMD) and metal leaching. AMD is one of mining’s most serious threats to the environment. This study investigated the short-term (8 days) and medium-term (27 days) drying rates and evaporative fluxes at the surface and near-surface of the Deilmann South waste-rock (DSWR) pile at the Key Lake uranium mine, northern Saskatchewan, using the gravimetric (GV) method and SoilCover (SC) model, respectively, during and following heavy rainfall events for the environment. The SC simulation results showed that during the weather-controlled stage (Stage I) of the first 5-day period of rainfall events, while the surface was wet, the potential evaporation (PE) was equal to the actual evaporation (AE) (i.e., AE/PE = 1). As the surface became drier on Day 6, the cumulative PE began to separate from the cumulative AE and the surface’s drying rate rapidly diverged from those at the deeper depths. This occurrence signaled the onset of the soil profile property-controlled stage (Stage II). As the drying continued, the surface became desiccated and the slow-rate drying stage (Stage III) was established from Day 7 onward. The SC-simulated AE results were compared to those measured using the eddy covariance (EC) method for the same test period at the DSWR pile in a different study. The comparison showed that the two methods yielded similar AE results, with 18% relative errors. The results of this study provided the opportunity to validate the SC model using actual data gathered under field conditions and to ascertain its ability to accurately predict the PE and AE at the surfaces of mine waste piles.

Patient Record Management System using Laravue

This study introduces a Patient Record Management System developed using Laravue, combining Laravel PHP and Vue.js. The system aims to streamline patient record handling, enhance data accessibility, and improve overall healthcare efficiency. Through an analysis of existing systems, the study emphasizes the need for Laravue's adoption. The methodology covers system design, development tools, and user feedback. Results include a comprehensive evaluation of system features, performance, and scalability. The Laravue-based system demonstrates its capability to efficiently manage patient records, ensuring secure and reliable healthcare data management.

Assessing the importance of drainage layers over geomembrane liners within engineered cover systems: Seven years of field monitoring at three mine waste rock piles

Geomembrane liners are commonly subject to defects that can allow water leakage through these openings and significantly undermine their performance. While defects are difficult to prevent and characterize, minimization of potential leakage can still be attained with appropriate lateral drainage over the liner. The objective of this study is to assess the performance of different drainage layer materials within HDPE-lined cover systems at three mine waste rock piles (WRPs) in the Sydney Coalfield, Nova Scotia, Canada. Natural soil, clean gravel and a geocomposite net were employed at the Summit, Victoria Junction and Franklin WRPs, respectively. Extensive field monitoring of precipitation (PPT), moisture content within the cover materials, and head of water above the liner, was performed. The head of water and moisture was consistently high at Summit throughout the year, while consistently low at Victoria Junction and Franklin, with the geocomposite net being just as effective as the gravel layer. Using typical assumptions of defect size/number, leakage rates at Victoria Junction and Franklin remained very low due to limited water head and flow gradient. Therefore, while the prevention of defects is highly challenging at HDPE-lined cover systems, potential defect leakage can be proactively controlled during cover system design with the implementation of adequate drainage layers above the liner.

Infrasound measurements of tornadoes and other severe storm events at close range

Recent experimental evidence suggests that, during tornadogenesis and through the life a tornado, acoustic waves at frequencies below human hearing (infrasound) are produced. To date, acoustic data required to identify the fluid mechanism responsible for this infrasound has been limited—often gathered by large fixed installations. The design and deployment of a mobile Ground-based Local Infrasound Data Acquisition (GLINDA) system was completed at Oklahoma State University to expand the number of samples and enable close-range measurements which would mitigate the measurement uncertainty associated with long distance atmospheric propagation. GLINDA has been deployed alongside Oklahoma-based media storm chasers since May 2020 and has already returned data over multiple severe weather events, including tornadic measurements acquired with GLINDA on 22 May 2020 in Lakin, Kansas. The GLINDA-equipped storm chaser vehicle can additionally provide acoustic data on other weather events such as wildfires and winter weather storms as the vehicle is appropriate for sustained, close observation of these environments. This presentation will cover system design, measurement capabilities, and acoustic production by select weather phenomenon.

Multicomponent landfill gas transport in soil cover: column tests and numerical modelling

A soil column test was carried out to investigate the mechanism of multicomponent landfill gas transport in loess. Four gas components, namely methane (CH4), carbon dioxide (CO2), oxygen (O2) and nitrogen (N2), were considered. Based on the dusty-gas model and mass balance equation, a one-dimensional transient model for multicomponent gas transport in landfill layered cover soils was then developed. Methane oxidation in the soil is also considered in the model. The numerical model was solved by the finite-element method-based program Comsol Multiphysics v5.1. The numerical results agree well with those observed from the soil column tests. The parameter analysis shows that ordinary diffusion plays an important role in the transport of multicomponent gases. For methane and carbon dioxide, ordinary diffusion contributes to 97% of the total transport flux in the shallow zone. The effect of ordinary diffusion decreases with the increase in the depth. Advection contributes to 37% of the flux at the bottom of the cover soil. The effect of Knudsen diffusion is relatively weak, which only contributes 0.5–12% to the total flux. This is due to the relatively high gas permeability of the soil. The contribution of advection is comparable to that of diffusion when the gas permeability increases up to 3 × 10−13 m2. The maximum methane oxidation rate is found to increase by a factor of 1.8, when influent flux increases from 1 × 10−5 to 1 × 10−4 (mol/m2)/s. The numerical solution can be used for the analysis of multicomponent landfill gas transport in the soils and the design of landfill cover systems with respect to gas pollution control.

The role of pore-gas dynamics in guiding reclamation practices

The storage and transportation of pore gasses in overburden and reclamation soil covers were evaluated using statistical analyses and finite difference numerical modelling to guide mine operators regarding practical issues surrounding the construction of overburden landforms, design of soil cover systems and management of reclamation sites. Factors that were found to impact gas transfer were soil moisture, soil temperature, differential pressures and dry bulk density of the overburden landform. Furthermore, the construction of the overburden landform appears to be more impactful to pore-gas dynamics than the design of the soil covers. Practicable recommendations can therefore be inferred to facilitate simultaneously methane oxidation in the uppermost horizon of the overburden while maintaining sufficient pore-gas oxygen in the plant-rooting zone of the soil covers to facilitate growth and survivability of reclamation vegetation. It is recommended that overburden be placed to approximately 1·6 Mg/m3. Mine operators should also recognise and manage extreme moisture conditions in the soil covers and uppermost overburden to mitigate restrictions in gas exchange and methane oxidation.

Fully coupled heat and water dynamics modelling of a reclamation cover for oil sands shale overburden

Numerical models of soil-water dynamics have been widely used in the design of soil cover systems for mine site reclamation; however, in most cases these models only consider water dynamics without consideration of heat dynamics. For cover systems in northern climates, such as those associated with oil sands mines in northern Alberta, Canada, freezing conditions exist for approximately 6 months of the year and snow melt comprises approximately 25% of annual precipitation. This study attempts to assess whether a fully coupled water and heat flow model (CM) provides additional insights into cover performance as compared with a water flow model (FM). The CM and FM are developed for a monitored reclamation cover constructed over oil sands shale overburden. The validated results indicated that the key limitation of the CM was its inability to simulate frozen ground infiltration. This limitation results in an overestimate of snow melt runoff and does not replicate the development of perched conditions on the shale overburden surface as a result of snow melt infiltration. The FM is also unable to simulate the observed infiltration of snow melt deep into the cover when snow melt is represented simply as surface precipitation in early spring following ground thaw. Both models are improved if snow melt infiltration is represented in the model by the preferential filling of macropores across the full depth of the cover and oxidized shale prior to ground thaw. This methodology is incorporated with the CM to produce a coupled water and heat model with enhanced infiltration (CM-EI), and with the FM to produce a flow model with enhanced infiltration (FM-EI). The CM-EI provided an improved simulation of soil temperature dynamics under frozen and unfrozen conditions, as well as soil water dynamics under unfrozen conditions, including the improved representation of the annual water balance components over each water year. Given the small difference in annual water balance components between the CM-EI and FM-EI modelling approaches (∼5 mm/year), it is concluded that a FM-EI provides the best tool with which to assess the performance of these reclamation covers.

Dessie Health Science College Store Management System

Dessie Health Science College (DHSC) uses manual process system for the store. When customers need to borrow an item, and return the borrowed item they must go to the office and record what they want manually, that’s way it is making the process too late. Which requires the employee to use paper based recording files to know the status of each customer and to perform the process in the system. The paper includes three chapters or phases. The first phase covers the introduction, which contains background, Existing system study, proposed system, objective of the project, benefits of the project, scope, methodology and significant of the project. The second phase covers the system features which contain existing system description, hardware requirement, software requirement, user requirement, system requirement, functional requirement, non-functional requirement, use case diagram, Use case description, activity diagram and sequence diagram. The third phase covers system design which include Deployment diagram, user interface design, ER diagram and Algorism design.

One-dimensional coupled model for landfill gas and water transport in layered unsaturated soil cover systems

Cover systems are used to prevent water infiltration into a waste body. They also play an important role in controlling landfill gas transport from the waste body to the atmosphere. It is important to assess the flux of landfill gas at the surface of a cover system by considering the coupled effects of rainwater infiltration and gas transport in the cover soils. We have developed a 1D mathematical model for coupled transient gas and water transport in unsaturated cover soils. The coupled model was solved by the finite element method. Results obtained by the proposed model agreed well with experimental data. Based on the proposed solution, the influences of gas pressure, gas permeability, and the thickness of the cover soils on soil gas concentration profiles were investigated. The difference in soil gas concentration reached up to 31% as the thickness of cover increased from 1 to 2 m. Gas concentration at a depth of 0.2 m decreased by 6% as the amplitude of atmospheric gas pressure fluctuation increased from 20 to 100 Pa. The gas concentration increased by only 3% when gas permeability increased by a factor of 2 for a relatively long period of gas migration (e.g., 60 h) under the given conditions. Results suggest that both diffusion and advection should be considered when estimating gas transport in unsaturated cover soils. The numerical model can be used in the design of cover systems in relation to gas breakthrough time, breakthrough concentration, and flux.

Conceptual Design of a Cover System for the Degmay Uranium Tailings Site

The Republic of Tajikistan has ten former uranium mining sites. The total volume of all tailings is approximately 55 million tonnes, and the covered area is more than 200 hectares. The safe management of legacy uranium mining and tailing sites has become an issue of concern. Depending on the performance requirements and site-specific conditions (location in an arid, semiarid or humid region), a cover system for uranium tailings sites could be constructed using several material layers using both natural and man-made materials. The purpose of this study is to find a feasible cost-effective cover system design for the Degmay uranium tailings site which could provide a long period (100 years) of protection. The HELP computer code was used in the evaluation of potential Degmay cover system designs. As a result of this study, a cover system with 70 cm thick percolation layer, 30 cm thick drainage layer, geomembrane liner and 60 cm thick barrier soil layer is recommended because it minimizes cover thickness and would be the most cost-effective design.

Water repellent soils: the case for unsaturated soil mechanics

Water repellent (or “hydrophobic” or “non-wetting”) soils have been studied by soil scientists for well over a century. These soils are typified by poor water infiltration, which leads to increased soil erosion and poor crop growth. However, the importance of water repellence on determining soil properties is now becoming recognised by geotechnical engineers. Water repellent soils may, for example, offer novel solutions for the design of cover systems overlying municipal or mine waste storage facilities. However, investigations into factors affecting their mechanical properties have only recently been initiated. This purpose of this paper is to introduce geotechnical engineers to the concept of water repellent soils and to discuss how their properties can be evaluated under an unsaturated soils framework. Scenarios in which water repellent properties might be relevant in geotechnical applications are presented and methods to quantify these properties in the laboratory and in the field examined.

Effects of biochar amendment on geotechnical properties of landfill cover soil.

Biochar is a carbon-rich product obtained when plant-based biomass is heated in a closed container with little or no available oxygen. Biochar-amended soil has the potential to serve as a landfill cover material that can oxidise methane emissions for two reasons: biochar amendment can increase the methane retention time and also enhance the biological activity that can promote the methanotrophic oxidation of methane. Hydraulic conductivity, compressibility and shear strength are the most important geotechnical properties that are required for the design of effective and stable landfill cover systems, but no studies have been reported on these properties for biochar-amended landfill cover soils. This article presents physicochemical and geotechnical properties of a biochar, a landfill cover soil and biochar-amended soils. Specifically, the effects of amending 5%, 10% and 20% biochar (of different particle sizes as produced, size-20 and size-40) to soil on its physicochemical properties, such as moisture content, organic content, specific gravity and pH, as well as geotechnical properties, such as hydraulic conductivity, compressibility and shear strength, were determined from laboratory testing. Soil or biochar samples were prepared by mixing them with 20% deionised water based on dry weight. Samples of soil amended with 5%, 10% and 20% biochar (w/w) as-is or of different select sizes, were also prepared at 20% initial moisture content. The results show that the hydraulic conductivity of the soil increases, compressibility of the soil decreases and shear strength of the soil increases with an increase in the biochar amendment, and with a decrease in biochar particle size. Overall, the study revealed that biochar-amended soils can possess excellent geotechnical properties to serve as stable landfill cover materials.

Physical and numerical modeling of infiltration including consideration of the pore-air phase

Infiltration is a vadose zone process of interest to a wide range of research communities including agriculture, soil physics, and geotechnical engineering. In geotechnical engineering, transient infiltration is important to moisture balance problems such as cover systems, capillary breaks, and landslide triggering. Design of cover systems, capillary breaks, and landslide analysis applications depend on accurate models for the transient pore pressure and moisture migration response under a wide range of environmental conditions. Infiltration is typically modeled using Richards’ equation, which assumes no impedance from the pore-air phase. However, if this assumption is invalid, the ground response during infiltration is significantly affected. An optically matched pore fluid – transparent soil, which allows for high temporal and resolution measurements of degree of saturation, was used to examine the effect of air entrapment on infiltration. Homogeneous and layered profiles were subjected to closed and open infiltration conditions. Following the completion of the experimental program, the results were simulated using a finite element program that allows for consideration of the air phase during infiltration. The results show the impact of ignoring the effect of air entrapment is to significantly underpredict the time to saturation and overpredict the pore pressure response.

Quantifying geomembrane wrinkles using aerial photography and digital image processing

Geomembranes are highly effective barriers, and are often a key component in the design of composite landfill liner and cover systems. During installation, solar exposure causes some types of geomembrane to buckle locally upwards and form networks of wrinkles (sometimes referred to as waves). These wrinkle networks may be significant in terms of increasing leakage through this barrier system if there is a hole at or near the wrinkle. In this paper, a novel method to quantify geomembrane wrinkles in the field is reported using low-altitude aerial digital photography and image processing techniques. The results of the analysis indicate that, at the date and time the aerial image was captured, the geomembrane contained 100 major wrinkles, which covered 13.9% of the total area of the exposed geomembrane. More importantly from a potential leakage perspective, over 90% of these wrinkles were found to be hydraulically connected over the entire field of view of the exposed geomembrane. This one hydraulically connected wrinkle was found to have an aggregate length of 520 m.

Seismic Response of a Composite Landfill Cover

The Olympic View Sanitary Landfill (OVSL) near Port Orchard, Washington, is a modern solid waste sanitary landfill covered, in part, by a composite cover system. The site was subjected to a free-field peak horizontal ground acceleration on the order of 0.16 g during the 28 February 2001 Moment Magnitude 6.8 Nisqually earthquake. To the knowledge of the writers, this is the first documented case history of a composite landfill cover shaken by strong ground motions. Postearthquake reconnaissance did not find any signs of earthquake-induced permanent displacement of the composite cover system. Accelerograms recorded within 1 km of the facility, the results of site-specific shear wave velocity measurements and laboratory interface shear testing, and these postearthquake observations provide a unique opportunity for a posteriori numerical analysis of this important case history. The seismic performance of the OVSL composite cover system was evaluated using four commonly used methods for seismic design of landfill cover systems. These methods include two simple screening procedures, a more rigorous screening procedure, and a decoupled equivalent-linear site response/Newmark-type permanent deformation analysis using the accelerograms recorded at the nearby strong motion station. The yield accelerations of the composite cover system, required for all four methods, were calculated using the results of construction quality assurance interface shear strength conformance testing. All four methods produce results consistent with the observed performance. However, the two simple screening procedures were significantly more conservative than the other two more rigorous methods.

A numerical study of soil cover performance

In the investigation of soil cover design options for final decommissioning of reactive mine waste, it is often necessary to analyze or predict the anticipated cover performance as a function of the cost of implementation, which is governed by the type, number and thickness of the layers in the cover system. An example of such investigation is presented in this study where one-dimensional evaporation from hypothetical moisture-retaining cover systems is simulated to assess the influence of several cover properties and hydrogeologic parameters on performance. The commercially available transient flow model, SoilCover, was used to compute suction and water content profiles for different cover design scenarios. The predicted water content profile and porosity of layers were then used to estimate the oxygen diffusion coefficients of the various layers. The oxygen diffusion coefficients were used to estimate oxygen flux through the cover systems. The oxygen flux was, in turn, related to the maximum acid flux. The studied cover and hydrogeologic parameters included soil type, thickness of barriers, and water table elevation. Two types of infiltration and oxygen barrier and two types of capillary layer with different thicknesses were studied. The water table was either kept constant at the base of the waste (tailings) or dropped by 0.5, 1, 2, and 3 m over 120 days. The results showed that the relationship between water table depression and the thickness of capillary layers, on one hand, and desaturation of the infiltration and oxygen barrier, on the other, is not linear. Relationships between oxygen flux and barrier thickness and between cost increase and performance improvement of the studied cover systems are presented. Finally, a method that outlines steps for site-specific and economically feasible design of multi-layer cover systems is introduced.

Working‐strain based design of landfill final cover systems

An approach to estimating the strain within geosynthetics placed on a landfill cover slope is emphasized. This approach adopts the analytical method for evaluating the geosynthetic tension within a geosynthetic/soil multi‐layered slope system. A review of the assumptions, solutions, and capabilities of this analytical method is summarized. The proposed approach is applied in stability analysis of an example landfill slope to evaluate the geosynthetic strains for different lengths of cover soil placement. The corresponding factors of safety are calculated using conventional slope stability analysis method. The results show that the relationship between the factor of safety and the slope length is convergent, while the relationship between geosynthetic strain and slope length is divergent. This analysis reveals that strainbased design is more rational.

40.4: Two‐Panel Architecture for Reflective LCD Projector

AbstractA new two‐panel architecture is discussed for projection systems based on liquid crystal on silicon (LCOS) panels. It is enabled by ColorLink's ColorSwitch™ and ColorSelect™ technologies. A first prototype has demonstrated performance of 325:1 contrast and 400 lumens using a UHP 120W lamp. This paper will cover system design and function, and will include a comparison of performance to alternative single and three panel approaches.

EXPERIENCES IN TRAINING SOFTWARE ENGINEERS TO PERFORM SYSTEMS ENGINEERING

AbstractThis paper presents the experiences in designing and delivering a systems engineering course for a project team consisting of software engineers who have, for the first time, total systems responsibility for a new computer system. The training objectives support the training mission which is to help assure project success.The training scope includes the systems engineering process, its management and its products beginning with needs analysis and continuing through system requirements specification, system design and producing software requirements and a software development plan.The course described here includes analysis of various aspects of computer systems; workload, functionality, man‐machine interface, security, and the “ilities” (reliability, maintainability, etc.). The course covers system design techniques and process models. The course covers how the results of analysis and design are qualified and how they are used in the construction of Government documents.