Standard Test Series Research Articles

Simulating Nonhydrostatic Atmospheres on Planets (SNAP): Formulation, Validation, and Application to the Jovian Atmosphere

A new non-hydrostatic and cloud-resolving atmospheric model is developed for studying moist convection and cloud formation in planetary atmospheres. It is built on top of the Athena++ framework, utilizing its static/adaptive mesh-refinement, parallelization, curvilinear geometry, and dynamic task scheduling. We extend the original hydrodynamic solver to vapors, clouds, and precipitation. Microphysics is formulated generically so that it can be applied to both Earth and Jovian planets. We implemented the Low Mach number Approximate Riemann Solver (LMARS) for simulating low speed atmospheric flows in addition to the usual Roe and HLLC Riemann solvers. Coupled with a fifth-order Weighted Essentially Nonoscillatory (WENO) subgrid-reconstruction method, the sharpness of critical fields such as clouds is well-preserved, and no extra hyperviscosity or spatial filter is needed to stabilize the model. Unlike many atmospheric models, total energy is used as the prognostic variable of the thermodynamic equation. One significant advantage of using total energy as a prognostic variable is that the entropy production due to irreversible mixing process can be properly captured. The model is designed to provide a unified framework for exploring planetary atmospheres across various conditions, both terrestrial and Jovian. First, a series of standard numerical tests for Earth's atmosphere is carried out to demonstrate the performance and robustness of the new model. Second, simulation of an idealized Jovian atmosphere in radiative-convective equilibrium shows that 1) the temperature gradient is superadiabatic near the water condensation level because of the changing of the mean molecular weight, and 2) the mean profile of ammonia gas shows a depletion in the subcloud layer down to nearly 10 bars. Relevance to the recent Juno observations is discussed.

Influence of cavity insulation on the fire resistance of light gauge steel framed walls

Light gauge steel framed (LSF) walls are used in fire compartmentation to prevent the spread of fire, smoke and toxic gases. The fire behavioural characteristics of non-load bearing LSF walls are different from those of load bearing walls. In non-load bearing LSF walls, fire penetration to the ambient side is to be prevented for insulation and integrity criteria whereas in load bearing walls, steel studs need to be protected from heat for structural adequacy also. This paper investigates the fire resistance of non-load bearing and load bearing LSF walls with and without cavity insulation. It presents the details of a series of standard fire tests conducted to investigate the effect of cavity insulation in both load bearing and non-load bearing LSF walls. The use of cavity insulation increased the fire resistance level (FRL) of non-load bearing walls, while it significantly reduced the FRL of load bearing walls. A finite element parametric study was then conducted for LSF walls lined with both single and double layers of plasterboards. Both thermal and structural fire performance results of LSF walls from finite element analyses are presented and compared in this paper. These results showed that FRL of cavity insulated non-load bearing LSF walls increases by 10–20 min, while it is significantly reduced for load bearing LSF walls with load ratios below 0.7. This study highlights both the beneficial and detrimental effects of cavity insulated LSF walls exposed to fire.

Compressibility of Compacted Clays Mixed with a Wide Range of Bentonite for Engineered Barriers

Compacted clay–bentonite mixtures are often used as compacted blocks and landfills in high-level radioactive waste repositories and clay liners, respectively. A better understanding of their compressibility behaviour is essential to guarantee the disposal safety. In this study, mixtures of clays and bentonite are used to investigate the compressibility and compaction behaviour. Three natural clays were selected with different physical characteristics, and clay–bentonite mixtures were prepared by mixing the bentonite content up to 50%. A series of standard compaction tests and consolidation tests were performed in the laboratory; the samples for the consolidation test were prepared at the optimum moisture contents and maximum dry unit weights. With increasing bentonite content, the liquid limit, plasticity index, optimum moisture content, initial void ratio and compression index of natural clays increase and maximum dry unit weight and yield stress decrease. It was observed that the effect of bentonite on geotechnical characteristics pronounced when bentonite content exceeded 10%. Correlations were also proposed to estimate the compression characteristics and compression curves of compacted clays using three physical parameters such as the initial void ratio, optimum moisture content and maximum dry unit weight.

Approaches to modeling occurrence of rolling contact fatigue damages in rails

Rolling contact-fatigue damages of rails along with their wear are the most common types of rail defects. In recent years, there have been significant changes in the distribution of rolling contact fatigue damages of rails especially on railways operating under heavy haul conditions.This paper is devoted to the overview of approaches to modeling of the occurrence of rolling contact fatigue (RCF) damages on working surfaces of rails. Four types of such approaches to modeling are considered. The first is based on the methods of contact mechanics. To realize it, the vehicle movement on the characteristic sections of the track is modeled, the forces acting in contact are determined, the contact problem is solved, and the values of the linear criterion of contact fatigue damage are determined. The required characteristics of rolling contact fatigue of the rail material are established on the basis of laboratory tests. The second approach uses the diagram of the adaptability of rail material to cyclic loads, proposed by K. Johnson, established on the basis of laboratory tests. The third approach uses criteria that have the physical meaning of the energy released at the contact as an index of the product of the tangential force in contact and relative slippage. In the fourth approach predicting the accumulation of plastic deformation under conditions of cyclic loading is performed on the basis of a series of standard tests of rail steels, including in the welded joint zone, and finite element modeling. In addition, there is also a probabilistic model, based on the assumption that it is possible to transfer the results of the RCF damage of rails on the experimental section of the road to any other site.As the conclusion the authors formulated directions for further studies on the formation and development of surface rolling contact fatigue defects in rails.

Linking Herbicide Dissipation to Soil Ecological Risk along Transmission Rights-of-Way in the Yukon Territory, Canada.

In the Yukon Territory, transmission rights-of-way (ROWs) are managed using brushing and mowing techniques alone. When cut, target species such as Michx. and spp. grow rapidly shortening maintenance cycles. Long-term vegetation control may be improved by integrating herbicide application. However, prior to implementation, the dissipation and toxicity of herbicides in northern latitudes needed to be assessed. The dissipation of Garlon XRT (triclopyr) and Arsenal Powerline (imazapyr) in soils was assessed at five ROW locations representative of the main ecoregion types where ROWs occur within the Yukon Territory. Soils from four sites were collected at 1, 30, and 365 d after treatment to determine persistence of herbicides for each of three application methods (backpack spraying, cut stump, and point injection). Increased sampling intervals were added to better determine the dissipation rate of each herbicide in Yukon Territory soils. Soil dissipation data were linked to a series of standardized toxicity tests, including three soil invertebrates (, , and ). Additionally, the dissipation of both herbicides from the target species L. was assessed at one site. Herbicide residues persisted in soils for longer than 365 d after treatment and longer than 30 d after treatment in . However, concentrations were below the concentration that would affect 25% of the invertebrate species tested. Weight of evidence and toxic exposure ratios were used to characterize the risks associated with herbicide application in northern latitudes and provided both qualitative and quantitative means to communicate the results to the public.

No evidence for detrimental effect of chemical castration on working ability in Swiss military dogs

Hormones influence the social behaviour of dogs. Castration of male dogs induces a reduction of testosterone and has been shown to affect social behaviours associated with aggression and reproduction. Changes in social behaviour could be critical in working dogs, which should be well trainable and behave reliably. It is currently unknown whether and how castration may affect the working ability of dogs. Besides surgical castration, chemical castration using a hormonal implant offers a possibility to castrate dogs temporarily. In the present study, we chemically castrated male Swiss military dogs and assessed their working abilities in comparison to intact males in a standard behavioural test series for Swiss military dogs (obedience, protection of the handler against an attacker, search of a hidden person in a building, reaction to social environment during a city walk). Chemical castration in Swiss military dogs had no measurable effect on any of the test situations in comparison to intact males.

Influence of fibre and matrix characteristics on properties and durability of wood–plastic composites in outdoor applications

The awareness of society on environmental issues has increased in recent years. This article focuses on the wood–plastic composites (WPCs), obtained from recycled plastics and natural fibres waste, and their application in architecture. In order to give some recommendations to architects regarding the choice of a WPC as an alternative to wood for uses in outdoor decking, a series of standardized physical, mechanical and chemical tests have been carried out on two commercial WPC materials: one with a polyvinyl chloride (PVC) – PVC matrix and rice husk filler and a second one with a polyethylene (PE) – PE matrix and pine wood reinforcement. Mechanical, thermal and ageing behaviour of these commercial WPC has been broadly studied. This research provides value information to find out which WPC material best support durability aspects, those that most concern in an architectural application of outdoor decking. In general terms, WPC developed by PVC matrix and rice husk as filler shown greater physical–mechanical properties, better resistance to chemical agents and greater resistance to ageing behaviour and changes in visual aspect.

Pragmatic competence and its relationship with the linguistic and cognitive profile of young adults with dyslexia.

The study assessed the pragmatic skills of 19 well-compensated Italian-speaking young adults with dyslexia compared with controls. A comprehensive pragmatic assessment tool was employed, targeting production and comprehension (Assessment of Pragmatic Abilities and Cognitive Substrates [APACS]). Participants were also administered a series of standardized tests to assess verbal and non-verbal cognitive abilities, including executive functions and social cognition tests. Data were analysed with the aim of understanding whether pragmatic abilities are compromised in dyslexia and of exploring associations between pragmatic performance and other cognitive domains. The performance of the dyslexia group was poorer than that of the control group in both expressive and receptive modalities. Data showed diffuse problems across several domains, with the greatest challenge posed by inferring nonliteral meanings, which indicates that pragmatic inefficiency is an important aspect of the linguistic and communicative profile of dyslexia in adulthood. Explorative correlations highlighted a relation between pragmatic performance and reading and vocabulary abilities, as well as between pragmatics and working memory. This suggests that pragmatic difficulties are strongly tied to the most distinctive aspects of dyslexia, namely, phonological awareness, verbal short-term memory, pseudo-word repetition, whereas the link with high-level executive functions and Theory of Mind is negligible.

Fire performance of load bearing LSF wall systems made of low strength steel studs

Light gauge steel frame (LSF) walls are commonly used in single and two storey residential and commercial buildings and modular based mid-rise building construction. They are lined with single or two layers of gypsum plasterboards and used with or without cavity insulation or noggings. This paper presents the details of a series of standard fire tests of load bearing LSF walls used in low-rise building construction to investigate the effects of using low strength steel studs, noggings and cavity insulation. The presence of cavity insulation significantly reduced the fire resistance level (FRL) of load bearing walls while the use of noggings increased the FRL, and these findings are considered valid for both low and high strength steel stud walls. Structural finite element models of fire tested walls were then developed using appropriate elevated temperature mechanical properties, validated using the fire test results and used in a parametric study of LSF walls made of both low and high strength steel studs. The results showed that FRL of low strength steel stud walls is reduced by about 25% in the common load ratio range in comparison with high strength steel stud walls, while their critical hot flange temperatures are reduced. These differences are due to the variations in their elevated temperature mechanical properties caused by the material composition. Reliable fire performance results of both low and high strength steel stud walls from finite element analyses and fire tests are presented and compared in this paper. This study has highlighted the importance of using accurate elevated temperature mechanical property reduction factors in numerical analyses and design of LSF walls.

Enrichment in the Sucker and Weaner Phase Altered the Performance of Pigs in Three Behavioural Tests.

Simple SummaryTwo important questions about the intensive housing of pigs concern whether young pigs require environmental enrichment to enhance their welfare, and from what age should enrichment be provided to pigs to achieve the benefit? We provided sucker and weaner pigs with enrichment in the form of blocks, which they could push around the floor of the pen, compared to no blocks (‘barren’ control). Behavioural and physiological responses of the pigs were then measured in a series of standard tests used to assess fear response, learning, and cognitive ability. Enrichment blocks modified the behavioural responses of pigs in the different tests, suggesting enriched pigs were more willing to explore novel environments and they had increased ability to learn. However, our enrichment treatment did not alter the pigs’ cortisol response, suggesting any differences due to enrichment were subtle. In contrast, the altered behavioural responses probably indicate that although pigs readily learned complex tasks and modify their behaviour to suit the current situation, there may be some potential benefits from enrichment when applied during the early weeks of a pig’s life that might have life-long benefits for the animal and its welfare.We tested the hypothesis that provision of enrichment in the form of enrichment blocks during the sucker and weaner phases would affect the behaviour of pigs. We measured the performance of pigs in an open field/novel object test, a maze test, an executive function test and the cortisol response of the pigs after exposure to an open field test. The provision of enrichment blocks altered the behaviour of the pigs in all three tests and these changes suggest an increased willingness to explore and possibly an increased ability to learn. The behavioural tests highlighted that young pigs have the capacity to learn complex tasks. Our findings support the notion that the benefits of enrichment cannot be evaluated by measuring the interactions the animal has with the enrichments in the home pen and it may simply be beneficial to live in a more complex environment. We have highlighted that the early rearing environment is important and that the management and husbandry at an early age can have long-term implications for pigs. The enrichment we used in this study was very simple, an enrichment block, and we provide evidence suggesting the provision of enrichment effected pig behavioural responses. Even the simplest of enrichments may have benefits for the welfare and development of young pigs and there is merit in developing enrichment devices that are suitable for use in pig production.

The Effects Of A Six-week Ketogenic Diet On The Performance Of Short-duration, High-intensity Exercise

There is much controversy surrounding the use of very high fat, low carbohydrate ketogenic diets and athletic performance. Specifically, it has been hypothesized that anaerobic activity, which is primarily fueled by ATP that is formed through the metabolism of carbohydrate sources, may be hindered when utilizing a ketogenic dietary approach. PURPOSE: The current study was designed to investigate how switching from a habitual diet to a ketogenic diet for 6 weeks would affect the performance of short-duration, high-intensity exercise. METHODS: Eight men and seven women (N = 15; 30.2 yr ± 4.11) were randomly assigned to either the ketogenic diet (KETO; n = 8) or the control group (CON; n = 7). All subjects were trained in CrossFit for at least 3 months prior to the study. Several measures of anaerobic performance were assessed at baseline and following 6 weeks utilizing the following series of standardized exercise tests: timed 500m row, Wingate Anaerobic Test, and 3-repetition maximum (3RM) deadlift. Aerobic capacity was also assessed by measuring VO2peak. Subjects continued their regular CrossFit training during the 6 week period and dietary intake was recorded. RESULTS: A significant increase (p < .05) in mean power output (MPO; W/kg) from baseline (M = 8.24 ± 1.15) to 6 weeks (M = 8.70 ± .82) was found the CON group. No significant interactions (p > .05) were found between diet and test time for any of the other measured exercise variables. No significant differences (p > .05) were found in the KETO group from baseline to 6 weeks in any of the measured exercise variables. No significant differences in body weight (lbs) were found from baseline to 6 weeks in either group (KETO; 183.8 ± 31.71 vs. 181.03 ± 30.28, CON; 166.38 ± 35.77 vs. 166.88 ±37.28). Attrition rate was 33% in the KETO group and 30% in the CON group. CONCLUSION: A 6-week ketogenic diet did not affect the performance of short-duration high-intensity exercise. Our data does not support the hypothesis that ketogenic diets induce detriments in the performance of activity that is anaerobic in nature. The current study took place over a 6 week period, allowing for keto-adaptation to occur; results may be different if a shorter time period were utilized.

Conformal and covariant Z4 formulation of the Einstein equations: Strongly hyperbolic first-order reduction and solution with discontinuous Galerkin schemes

We present a strongly hyperbolic first-order formulation of the Einstein equations based on the conformal and covariant Z4 system (CCZ4) with constraint-violation damping, which we refer to as FO-CCZ4. As CCZ4, this formulation combines the advantages of a conformal and traceless formulation, with the suppression of constraint violations given by the damping terms, but being first order in time and space, it is particularly suited for a discontinuous Galerkin (DG) implementation. The strongly hyperbolic first-order formulation has been obtained by making careful use of first and second-order ordering constraints. A proof of strong hyperbolicity is given for a selected choice of standard gauges via an analytical computation of the entire eigenstructure of the FO-CCZ4 system. The resulting governing partial differential equations system is written in non-conservative form and requires the evolution of 58 unknowns. A key feature of our formulation is that the first-order CCZ4 system decouples into a set of pure ordinary differential equations and a reduced hyperbolic system of partial differential equations that contains only linearly degenerate fields. We implement FO-CCZ4 in a high-order path-conservative arbitrary-high-order-method-using-derivatives (ADER)-DG scheme with adaptive mesh refinement and local time-stepping, supplemented with a third-order ADER-WENO subcell finite-volume limiter in order to deal with singularities arising with black holes. We validate the correctness of the formulation through a series of standard tests in vacuum, performed in one, two and three spatial dimensions, and also present preliminary results on the evolution of binary black-hole systems. To the best of our knowledge, these are the first successful three-dimensional simulations of moving punctures carried out with high-order DG schemes using a first-order formulation of the Einstein equations.

Effects of reclaimed asphalt materials on geotechnical characteristics of recycled concrete aggregates as a pavement material

The use of recycled concrete aggregates (RCAs) as an unbound pavement material is a perfect alternative to effectively manage the construction and demolition (C&D) wastes. However, the presence of constituents in RCA is led for inconsistent properties. The reclaimed asphalt pavement (RAP) material is one of the major constituents that can be mixed at the recycling process of demolished concrete. Therefore, this study aims to investigate the effects of RAP as a constituent in RCA, on its characteristic properties as an unbound pavement material. To achieve the objectives of the study, five RCA samples were produced by mixing different percentages of RAP by weight. A series of standard laboratory tests were conducted on each sample. The results were then compared with the properties of standard granular pavement materials specified by Queensland Department of Transport and Main Roads (QDTMR), Australia. The analysis depicted that the presence of RAP as a constituent in RCA up to 15% was not significantly affected on the physical properties of RCA as an unbound pavement material.

Effects of nano-layered silicates on mechanical and chemical properties of acrylic-melamine automotive clear coat

PurposeMechanical and chemical properties of acrylic-melamine automotive clear coat in the presence of different percentages of well dispersed nano-layered sodium montmorillonite (Na-MMT) silicate particles were investigated. For this purpose, prepared dry clear coat film samples were subjected to the entire standard test series, usually carried out in automotive coating industry.Design/methodology/approachEffects of adding different percentages of nano-layered silicate on mechanical and chemical properties of acrylic-melamine automotive clear coat were investigated. To increase the compatibility of nanoclays with polymer matrix of clear coat, the surface of nanoclays was modified by benzalkonium chloride as a cationic surfactant. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used for characterization and comparison between clays before and after modification, and also after dispersion in coating. Prepared dry clear coat film samples subjected to the test series are usually carried out in automotive coating industry.FindingsThe results indicated that incorporation of 1 and 2 Wt.% of nano-layered silicate caused desired improvement in chemical and physical properties of the acrylic-melamine clear coat. Increasing the percentage of nanoclay to over 2 Wt.% caused damage in some properties such as hardness, cupping and gloss.Research limitations/implicationsAll materials and methods were used in this research are industrial grade. Therefore, the introduced modified clear coat sample has potential for commercial production as an automotive clear coat.Originality/valueAs far as it was searched in the literature, effects of adding nanoclay particles on mechanical and physical properties of different clear coats, such as epoxy clear coat, have been investigated in a few researches, but in this research, common and special tests which are necessary in automotive coating industry have been ignored. In the present study for the first time, acrylic-melamine clear coat was subjected to modification using nano-clay, and also, the most common industrial test methods were used for investigation of mechanical and chemical properties.

Quadratic serendipity finite elements over convex polyhedra

SummaryThe conventional approach to construct quadratic elements for an n‐sided polygon will yield n(n+1)/2 shape functions, which increases the computational effort. It is well known that the serendipity elements based on isoparametric formulation suffers from mesh distortion. Floater and Lai proposed a systematic way to construct higher‐order approximations over arbitrary polygons using the generalized barycentric and triangular coordinates. This approach ensures 2n shape functions with nodes only on the boundary of the polygon. In this paper, we extend the polygonal splines approach to 3 dimensions and construct serendipity shape functions over hexahedra and convex polyhedra. This is done by expressing the shape functions using the barycentric coordinates and the local tetrahedral coordinates. The quadratic shape functions possess Kronecker delta property and satisfy constant, linear, and quadratic precision. The accuracy and the convergence properties of the quadratic serendipity shape elements are demonstrated with a series of standard patch tests. The numerical results show that the quadratic serendipity elements pass the patch test, yield optimal convergence rate, and can tolerate extreme mesh distortion.

STRENGTH AND DEFORMATION CHARACTERISTICS OF EPS BEAD-MIXED SAND

In this research, a study on strength and deformation characteristics of expanded polystyrene(EPS) bead-mixed sand was comprehensively conducted. A series of standard Proctor compaction tests wereconducted to determine the proper amount water for use in the mixing between EPS bead and sand at thevolumetric ratio of 1:1. A special series of drained triaxial compression tests were performed on the sand-EPSbead mixture (SEM) specimens. Various loading histories, consisting of: i) monotonic loading (ML) atdifferent constant strain rates; ii) sustained (creep) loading (SL); iii) cyclic loading with small strain-amplitude(CL); and iv) stepwise changes in the strain rate during otherwise ML, were employed in this study. Theseloading histories were used to evaluate the elastic and viscous properties of the SEM. Then these propertieswere also compared with the ones obtained from the sand alone under similar loading conditions. It is foundthat the elastic and viscous properties of the SEM are qualitatively similar to those of sand alone. They aredifferent in terms of quantity. A non-linear three-component (NTC) model was used to simulate the elastoviscoplastic deformations of the SEM. The simulations are well successful by using the model parametersdetermined especially for the SEM sand under the conventional model framework.

Oligoamide grafted with perfluoropolyether blocks: A potential protective coating for stone materials

Abstract In order to mitigate the decay phenomena induced by liquid water adsorption and penetration, new protective coating agents with high hydrophobicity, photo-oxidative stability and good solubility in non-toxic solvents are needed. In the present study, a partially fluorinated oligoadipamide bearing pendant PFPE segments (FAD) together with two diamides i.e., ethylenediamide (DC2) and hexamethylenediamide (DC6) incorporating perfluoropolyether (PFPE) segments, were synthesized via condensation reactions. The diamides are only soluble in chlorofluorocarbons, while the oligoadipamide is soluble in alcohols and hydro-alcoholic solvents e.g., ethanol, 2-propanol. The polymerization degree, together with the molecular weight and molecular weight distribution of oligoethylene-adipamide evaluated by 1H NMR spectroscopy, was found very low which allowed to obtain a partially fluorinated amide with a high fluorine content (57%). To determine the protective performance of the new FAD, a series of standard tests were conducted on Lecce stone and Carrara marble samples. Regarding water repellence, compared with a commercial fluoroelastomer tested as a reference material, FAD demonstrated much higher water repellence when applied on Carrara marble samples, and comparable hydrophobic effect when applied on Lecce stone samples. In comparison with the two diamides, tested on Lecce stone, the oligoamide manifested similar protective efficacy with a much less amount applied (15 g/m2 versus 154/150 g/m2). In addition to its high hydrophobicity, FAD also preserved the original vapor permeability and chromatic features of coated surfaces. With these favorable properties, this new oligomeric product is ought to be proposed as protective coating material for stone heritage.

Adherence to diabetic eye examination guidelines in Australia: the National Eye Health Survey.

To determine adherence to NHMRC eye examination guidelines for Indigenous and non-Indigenous Australian people with diabetes. Cross-sectional survey using multistage, random cluster sampling. Thirty randomly selected geographic sites in the five mainland Australian states and the Northern Territory, stratified by remoteness. 1738 Indigenous Australians aged 40-92 years and 3098 non-Indigenous Australians aged 50-98 years were recruited and examined between March 2015 and April 2016 according to a standardised protocol that included a questionnaire (administered by an interviewer) and a series of standard eye tests. Adherence rates to NHMRC eye examination guidelines; factors influencing adherence. Adherence to screening recommendations was significantly greater among non-Indigenous Australians (biennial screening; 77.5%) than Indigenous Australians (annual screening; 52.7%; P <0.001). Greater adherence by non-Indigenous Australians was associated with longer duration of diabetes (adjusted odds ratio [aOR], 1.19 per 5 years; P = 0.018), while increasing age was associated with poorer adherence in non-Indigenous Australians (aOR, 0.70 per decade; P = 0.011). For Indigenous Australians, residing in inner regional areas (aOR, 1.66; P = 0.007) and being male (aOR, 1.46; P = 0.018) were significant factors positively associated with adherence. More than three-quarters of non-Indigenous Australians with diabetes and more than half of Indigenous Australians with diabetes adhere to the NHMRC eye examination guidelines. The discrepancy between the adherence rates may point to gaps in the provision or uptake of screening services in Indigenous communities, or a lack of awareness of the guidelines. A carefully integrated diabetic retinopathy screening service is needed, particularly in remote areas, to improve adherence rates.

Preliminary Study on The Potential of Hybrid Rice Husk with Kapok Fiber and Hybrid Rice Husk with Coconut Fiber as Landfill Liner Material

Abundance of agricultural waste in Malaysia namely rice husk (RH), kapok fiber (KF) and coconut fiber (CF) has been increasing over the years. This cause disposal problem and air pollution problem from burning activity. In line with the Malaysian Government Policy on the application of green technology concept through the 5R's practice, this agricultural waste has a potential to be commercialized as material for landfill liner. A factor that governs the workability of landfill liner materials is the permeability should be less than 1x10 -9 m/s. Therefore, a low permeability material needs to be installed to minimise the environmental impact on the leachate intrusion into groundwater. A series of standard tests to find environmental and geotechnical properties such as atterberg limit test (liquid limit, plastic limit, compaction test), permeability test (falling head method), leachate characteristics and heavy metal test were conducted at various ratio of hybrid materials (KC:RH and KC: CF in the ratio of 1:1 and 1:2 respectively). Experimental results confirmed that the hydraulic conductivity of the mixture of KC:RH:KF in the ratio of 1:1:1 is 7.29 x 10- 11 m/s was less than 10 -9 m/s, satisfying the requirement for landfill liner materials. Heavy metal testing showed that this hybrid material (RH:KF and RH:CF for ratio 1:2) were able to reduce at least 50 % of the leachate contaminants. The proposed hybrid materials (RH:KF and RH:CF) is a green material for the landfill (as it can improve heavy metal adsorption), increase the workability of the landfill by improving the conductivity of the conventional liners), minimizing manpower on site (no need expertise for installation) and reduction in cost (in terms of the use of waste materials).

A Numerical Study on Dilation of a Saw-Toothed Rock Joint Under Direct Shear

The roughness of a rock joint gives rise to the phenomenon of dilatancy. Numerous studies have been conducted to examine their dilation behaviour partly due to its importance as a stabilising effect. While previous researchers have improved the understanding of dilation behaviour and identified important parameters affecting the magnitude of dilation during shear, there is still a lack of quantification of the method for predicting the dilation angle. This paper describes a systematic parametric study to investigate the effect of relative normal stress and geometric properties on the dilation of a saw-toothed rock joint by using a distinct element method code with Voronoi tessellation. The applicability of the numerical model was assessed by calibration with a series of standard laboratory tests. The simulation results indicate that the magnitude of relative normal stress plays the most important role among parameters and quantify how much those parameters affect the dilation behaviour during shear. The findings of this study, presented in a normalised relation, can be employed when dilation values need to be determined in rock engineering practice.