Study on the adsorption of Cr( Ⅵ) onto landfill liners containing granular activated carbon or bentonite activated by acid

The adsorption capacity of landfill liners containing granular activated carbon (GAC), or bentonite activated by acid, for Cr(VI) was investigated by batch testing. The results show that both GAC and activated bentonite could be used as sorptive amendments for trapping Cr(VI) in landfill liners. The Cr(VI) sorption to GAC and activated bentonite is much greater than Cr(VI) sorption to natural clay. The adsorption capacity of Cr(VI) onto all the soils increases with increasing temperature; adsorption capacity is also significantly influenced by soil-solid concentration. As the soil-solid concentration increases the adsorption capacity first decreases logarithmically, but then stabilizes when the soil-solid concentration exceeds a critical value (e.g. 400 g/L). Permeability tests were conducted in the laboratory. The results indicate that the hydraulic conductivity of landfill liners containing GAC or activated bentonite can meet the engineering requirement of 1 nm/s. One-dimensional transport simulations for Cr(VI) were performed to evaluate the effect of GAC and activated bentonite on landfill liners. The results of the simulations indicate that landfill liners containing GAC, or activated bentonite, significantly retard the transport of Cr(VI) relative to a conventional clay liner.

Study on Swell Pressure Stress of Bentonite in Geosynthetic Clay Liners

The geosynthetic clay liner （GCL） is a kind of waterproofing material used widely in engineering. The waterproof mechanism is understood in terms of bentonite particles becoming water-obstruct colloid layers after they sorb water and swell. The swell pressure stress, however, has not been determined directly till now. In our experiment, swell pressure stress of the GCL under saturated water-sorbing condition was measured directly using a custom-made instrument. The results show that （1） the instrument designed by the authors performs satisfactorily and the test results are reproducible; and （2） the trend line of swell pressure stress variation with time can be divided into three segments. The first segment is characterized by a quick increase of the swell force in the first 0-50 hours. The swell pressure stress increases by 7.00×10^-4-1.00×10^-3 MPa/h. The second segment shows a slow increase of the swell pressure stress from the 50th to 1730th hour. The swell force increases by 7.54×10^-6-2.02×10^-5 MPa/h. The third segment is characterized by a little variation in swell pressure stress after 1730 hours. In this segment, the average value of the swell pressure stress measurements is 0.0719 MPa and the maximum value is 0.0729 MPa. It is suggested that the swell pressure stress is mainly raised by water entering pores among montmorillonite particles and interstitial layers in individual montmorillonite crystals, leading to an increase of volume.

Influences of liners and magnetic flux concentrator on induced Joule heat in hot extruded billet

In the production of pipes by hot extrusion method,billets should be heated to a certain temperature before hot extrusion by induction heating. The segmented liners in the induction furnace can possibly affect the circumferential Joule heat generation,thus leading to an uneven temperature field. The commonly used magnetic flux concentrators （MFC） can increase the temperature on both ends of the billet. In this paper ,the possible effect of liners and the factors affecting the utilization of the MFC,including the permeability,dimension and position,are all numerically studied and determined.

Shear Strength Behavior of Two Landfill Clay Liners

Direct shear tests were conducted to obtain both the shear strength ofcompacted clay liners (CCLs) specimens and the interface shear strength between compacted clay linerand base soil. These experiments were conducted under the conditions of five different watercontents. The experimental results show that shear strength of both CCLs and CCLs/base interfacedecreases with the increase in the water content of CCLs and base soil. In addition, the considerateconcentration of NaCl in leachate has no deteriorating effect on the shear strength of liners.Triaxial shear tests were also conducted on clay liner specimens to obtain total and effective shearstrength under a fast compression. The shear strength parameters with total stress are φ=18. 5°and c=30 kPa for clay-bentonite, and φ=48. 5° and c=90 kPa for sand-bentonite and those witheffective stress are φ'= 27. 2° and c'=25 kPa for clay-bentonite, and φ'=35° and c'=100 kPa forsand-bentonite, respectively. These results indicate that the compacted clay-bentonite shows normalconsolidation, but that the compacted sand-bentonite exhibits over-consolidation.

Objective-level resilience assessment of circular roadway tunnels with reinforced concrete liners for vehicle fire hazards

A framework is presented to quantify the objective-level resilience of reinforced concrete liners of circular tunnels when exposed to enclosed vehicle fire hazards.By assessing the loss of functionality due to fire-induced damage,the framework enables a decision-basis evaluation of the efficiency of various fire mitigation methods for spe-cific tunnel conditions.In this study,the fire-induced damage of concrete tunnel liners due to strength loss and spalling is stochastically simulated and classified based on typical post-fire repair procedures and damage evalu-ation.The resilience assessment is conducted using Monte Carlo Simulation in combination with a fast-running tool for calculating the thermal impact from vehicle fires on the inside surface of the tunnel liner(developed by the authors in previous work).The proposed approach accounts for uncertainties associated with both the vehicle fire(particularly the combustion energy)and the tunnel conditions(i.e.,geometry,dimensions,and the presence of longitudinal ventilation and/or fixed fire-fighting systems(FFFS)).A parametric case study is used to quantitatively demonstrate the effectiveness of FFFS for reducing post-fire losses of tunnel functionality.Other parameters such as tunnel dimensions,traffic restrictions for vehicles with heavy fire hazard risk,and installation or upgrade of the tunnel ventilation system show somewhat less effectiveness for reducing fire-induced damage.

Slagging characteristics of molten coal ash on silicon-aluminum combustion liners of boiler

In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan electron microscopy and energy dispersive X-ray analysis, and the transformation characteristics of the compositions and crystal phases were studied. The results show that the size of slag granules decreases as the slagging temperature increases; the crystallinity of coal ash I reduces to about 48.6% when the temperature is increased up to 1 350 ℃, and that of the coal ash II reduces to about 65% when the temperature is increased up to 1 500 ℃; the encroachment of molten coal ash to the combustion liner is strengthened. At the same time, the diffusion and the segregation of the compositions in combustion liners have selectivity, which is in favor of enhancing the content of crystal phases, weakening the conglutination among molten slag compositions and combustion liner, and avoiding yielding big clinkers. But the diffusion of the compositions in combustion liners increases the porosity and decreases the mechanical intensity of combustion liner, and makes the slag encroachment to the liner become more serious.

The Structure of Narrow-Line Region in LINERs

Low-ionization nuclear emission regions （LINERs） are present in a large fraction of local galaxies, while their connection to the more luminous active galactic nuclei （AGN） remains elusive. We analyze the narrow band images obtained by the Hubble Space Telescope （HST） in Hα＋[NII] and/or [OIII] band for 23 LINERs and low luminosity Seyfert galaxies in the sample of the Palomar Optical Spectroscopic Survey of nearby galaxies in an attempt to resolve the structure of Narrow Emission Line Regions （NLRs） of these objects. In all cases, NLRs are well resolved and their morphology differs from object to object. Clumps, linear structure, spiral arms or a ring are detected in a large fraction of the objects, while there is no significant difference between Seyfert galaxies and LINERs. We find that the NLR size and the narrow line luminosity are strongly correlated for both LINERs and low luminosity Seyfert galaxies, and that the size of Ha＋[NII] emission line region scales with Ha luminosity as RNLR ∝ LHα^0.44＋0.06, consistent with an extension of the NLR size-luminosity relation defined for luminous Seyfert galaxies and quasars, to two orders of magnitude lower in luminosity and to lower activity levels. Our results suggest that NLRs in LINERs are similar to those of Seyfert galaxies, and they are powered by the central active galactic nucleus.

Hydration swelling characteristics of needle-punched geosynthetic clay liners

A series of confined swell tests were conducted on a needle-punched geosynthetic clay liner (GCL) with tap water as the hydration medium. The effects of the static confining stress on the swelling characteristics of GCLs and the hydration time under different confining stresses were explored. Increasing the static confining stress led to: shorter hydration time; smaller final GCL height; less final GCL bulk void ratio; smaller final bentonite moisture content. The confined swell pressure determined for the tested GCL was 82.2 kPa, and the relationships between confining stress, final bulk void ratio (or final GCL height, final bentonite moisture content) were attained through the analyses of the confined swell test results in this study.

Potential Calculation on the Oil-Gas Pipeline with Geosynthetic Clay Liners Based on BEM

Put geosynthetic clay liners around underground oil-gas pipelines can reduce the potential damage to environment but it will also affect the distribution of cathodic protection current. Geosynthetic clay liners can be regarded as anisotropic soil structure and the potential distribution on the pipeline between two adjacent cathodic protection stations was calculated based on boundary element method (BEM). The calculation results indicate that potential distribution on the pipeline with geosynthetic clay liner is lower than before. A 1500 m built pipeline with geosynthetic clay liners was selected to be calculated and to perform field test, which shows that the calculation results tally well with the field test results and the validity of the arithmetic in this paper was verified.

Suitability of Irbid Clay as Compacted Liners for Landfill, Jordan

The goal of this study is to investigate the possibility of using the Irbid city clayey soil as compacted clay liner. The geotechnical properties and the permeability characteristics of compacted clayey soil sample obtained from the eastern part of Irbid city were determined to evaluate their suitability as compacted clay liner. Falling head permeability test, unconfined compressive strength and volumetric shrinkage test were conducted on soil samples that were compacted at about 0% and 3% wet of its optimum water content. The leakage rates expected through clay-only and composite geomembrane-clay liners were determined. It could be concluded based on the results of the geotechnical tests and leachate rate calculations that Irbid clay is appropriate to be used as compacted landfill liner material.

Seasonal variations and the influence of geomembrane liners on the levels of PBDEs in landfill leachates,sediment and groundwater in Gauteng Province,South Africa

In the present study,the seasonal concentrations of polybrominated diphenyl ethers(PBDEs)in leachate and sediment samples,and the influence of geomembrane liners on PBDE levels and the extent of their infiltration into groundwater on selected landfill sites in Gauteng Province,South Africa were determined.Leachate and sediment samples were collected from seven operational landfill sites namely:Goudkoppies,Robinson Deep,Marie Louis,Soshanguve,Onderstepoort,Hatherly and Garankuwa from Johannesburg and Pretoria,in winter and summer.Groundwater samples were collected from monitoring boreholes from two landfill sites.Liquid-liquid and Soxhlet extraction techniques were employed for the extraction of leachate and groundwater,and sediment respectively using dichloromethane.The extracted samples were subjected to column clean up and,thereafter,analysed using gas chromatographyemass spectroscopy(GC-MS).PBDEs selected for the study were:BDE-17,-28,-47,-100,-99,-153,-154,-183 and-209.The P9PBDE concentrations in leachate samples for winter and summer ranged from 0.316e1.36 ng L-1 and 0.560e1.08 ng L-1 respectively.The P9 PBDE concentrations obtained for sediment in winter and summer were 3.00e4.91 ng g-1 and 2.50e3.71 ng g-1 respectively.Winter samples exhibited higher(p<0.05)concentrations for both leachate and sediment samples compared to summer samples.This trend was attributed to high precipitation rate in summer which may have infiltrated into the landfills,subsequently diluting the leachate and sediment samples.In contrast,the winter period is generally dry and PBDEs are,therefore,more likely to be concentrated.The concentrations of PBDEs in leachate and sediment samples were higher in landfill sites with geomembrane liners compared to those without liners.Groundwater samples taken from the vicinity of selected landfill sites without geomembrane liners exhibited high concentrations of P9PBDEs,indicating possible migration of PBDEs from landfill site into groundwater.Pearson correlation(r)and statistical significant t-test(p)for the PBDE congeners versus dissolved organic carbon(DOC)resulted in positive moderate interactions with a statistical significance for most congeners.Suggesting that there is a possible influence of organic carbon on the levels of PBDEs.

An analytical solution to contaminant transport through composite liners with geomembrane defects

To investigate the performance of landfill composite liner system,a one-dimensional model was developed for solute transport through composite liners containing geomembrane defects.An analytical solution to the model was obtained by the method of Laplace transformation.The results obtained by the presented solution agree well with those obtained by the numerical method.Results show that leachate head and construction quality of geomembrane(GM) have significant influences on the performance of the composite liners for heavy metal ions.The breakthrough time of lead decreases from 50 a to 19 a when the leachate head increases from 0.3 m to 10 m.It is also indicated that the contaminant mass flux of volatile organic compounds(VOCs) induced by leakage can not be neglected in case of poor construction quality of the landfill barrier system.It is shown that diffusion coefficient and partition coefficient of GM have great influences on solute transport through composite liners for VOCs.The breakthrough time of heavy metal ions will be greatly overestimated if the effects of diffusion and adsorption of clay and geosynthetic clay liner(GCL) are neglected.The composite liner consisting of a geomembrane and a GCL provides a poor barrier for VOCs.The presented analytical solution is relatively simple to apply and can be used for preliminary design of composite liners,evaluating experimental results,and verifying more complex numerical models.

Seismic stability and permanent displacement of landfill along liners

The three-part wedge limit equilibrium method for seismic stability analysis of the landfill along liners is presented. The approximate solutions of the factor of safety and the yield acceleration coefficient are obtained. Parametric studies show that the interface strength of liners, the shear strength of waste and the height of retaining wall can influence the seismic stability of landfill along liners. The density and the shear wave velocity of the field waste are obtained by the borehole investigation and the spectral analysis of surface wave (SASW), respectively. The strain-dependent shear modulus and damping ratio of the artifical waste are obtained by the moderate-scale dynamic triaxial tests. The onedimensional (1D) equivalent linear dynamic response analysis is used to calculate the horizontal equivalent seismic coefficient-time history of the sliding landfill during earthquake. The seismic permanent displacement of the landfill along liners with different site conditons and heights is evaluated by the Newmark method. The catculated results show that ratio of ky /kmax, site conditions, the amplitude and frequency content of the bedrock motion can affect the seismic permanent displacement of the landfill along liners in some degree. Finally, the seismic stability and permanent displacements of three expanded configurations of a certain landfill case are analyzed.

Investigation of straightforward impedance eduction method on single-degree-of-freedom acoustic liners

In order to address the current aircraft noise problem, the knowledge of impedance of acoustic liners subjected to high-intensity sound and grazing flow is of crucial importance to the design of high-efficiency acoustic nacelles. To this end, the present study is twofold. Firstly, the StraightForward impedance eduction Method(SFM) is evaluated by the strategy that the impedance of a liner specimen is firstly experimentally educed on a flow duct using the SFM, and then its accuracy is checked by comparing the numerical prediction with the measured wall sound pressure of the flow duct. Secondly, the effects of grazing flow and high-intensity sound on the impedance behavior of two single-layer liners are investigated based on comparisons between educed impedance and predictions by three impedance models. The performance of the SFM is validated by showing that the educed impedance leads to excellent agreement between the simulation and the measured wall sound pressure for different grazing flow Mach numbers and Sound Pressure Levels(SPLs) and over a frequency range from 3000 Hz down to 500 Hz. The grazing flow effect generally has the tendency that the acoustic resistance exhibits a slight decrease before it increases linearly with an increase in Mach,predicted successfully by the sound-vortex interaction theoretical model and the Kooi semi-empirical impedance model. However, the Goodrich semi-empirical impedance model gives only a simple linear relation of acoustic resistance starting from Mach zero. Additionally, when the SPL increases from 110 to 140 d B in the present investigation, the acoustic resistance exhibits a significant increase at all frequencies in the absence of flow; however, the resistance decreases slightly under a grazing flow of Mach 0.117. It indicates that the SPL effect can be greatly inhibited when flow is present,and the grazing flow effect can be reduced partly as well at a relatively high SPL.

Low capacitance and highly reliable blind through-silicon-vias(TSVs) with vacuum-assisted spin coating of polyimide dielectric liners

Low-k and high aspect ratio blind through-silicon-vias （TSVs） to be applied in ＂via-last/backside via＂ 3-D integration paradigm were fabricated with polyimide dielectric liners formed by vacuum-assisted spin coating technique. MIS trench capacitors with diameter of-6 μm and depth of-54 μm were successfully fabricated with polyimide insulator step coverage better than 30%. C-V characteristics and leakage current properties of the MIS trench capacitor were evaluated under thermal treat- ment. Experimental results show that, the minimum capacitance density is around 4.82 nF/cm2, and the leakage current density after 30 cycles of thermal chock tests becomes stable and it is around 30 nA/cm2 under bias voltage of 20 V. It also shows that, the polyimide dielectric liner is with an excellent capability in constraining copper ion diffusion and mobile charges even un- der test temperature as high as 125℃. Finite element analysis results show that TSVs with polyimide dielectric liner are with lower risks in SiO2 interlayer dielectric （ILD） fracture and interfacial delamination along dielectric-silicon interface, thus, higher thermo-mechanical reliability can be expected.

Penetration performance of W/Cu double-layer shaped charge liners

Two kinds of W/Cu double-layer shaped charge liner（SCL） were prepared by chemical vapor deposition（CVD） combined with electroforming technique： A SCL with W inner layer and Cu outer layer, B SCL with Cu inner layer and W outer layer. The penetration properties of A and B SCLs were researched. The results show that the two SCLs can form continuous jet and the tip velocities of A and B jets are 7.4 and 6.3 km s^（-1）, respectively. The kinetic energy density（5.3 9 1011 J m-3） of A jet tip increases by 194.4 %compared with that（1.8 9 1011 J m-3） of B jet tip. B jet,however, exhibits deeper penetration depth at the same experimental conditions. The chemical component and microstructure of the area nearby the ballistic perforation were researched. Component analysis shows that both the jets are formed only from inner layer metal. Microstructure analysis shows that martensite and intermetallic form around ballistic perforation penetrated by A SCL due to the intensive interaction between W jet and steel target. The two kinds of newly formed ultrahard phases also hinder the jet from penetrating target further. As a result of relatively alleviative interaction between Cu jet and target, only solid solution rather than ultrahard phases forms around ballistic perforation penetrated by B SCL.

Correlation of field and experimental test data of wear in heavy commercial vehicle brake liners

The correlation between the wear behavior of a heavy commercial vehicle (HCV) brake liner tested under controlled laboratory conditions and that in actual field conditions is investigated.A brake liner study for friction and wear is performed on an inertia brake dynamometer (IBD) at different temperatures (200 ℃,250 ℃,and 300 ℃) using 6000 brake actuations in a laboratory.The total wear loss of the brake liner at three different temperatures for 6000 brake actuations in IBD is found to be 1.12 mm.The actual field test is conducted on four different HCVs,namely,a city bus (CB),a high speed bus (HSB),a highway truck (HWT),and a tipper lorry (TL).These HCVs run at different terrain/traffic conditions and load conditions.When comparing the predicted life of the brake liner through the IBD test with the actual life of the brake liner in different HCVs,a vast difference is observed.Due to the large variation of liner life observed between the actual and predicted tests,an extensive field test is conducted.In the field test,the liner with identical formulation is fitted in the four types of HCVs.The predicted life of the liner using IBD is then correlated with the field test observation and a correlation factor is determined.Based on this correlation factor,the predicted life of the liner and the achieved life on the HCV are found to be fairly close.This study will be useful to design the friction material formulation and to predict the actual life of the brake liner for various HCVs.

Impact of surface-reflected seismic waves on the seismic isolation performance of circular tunnel isolation layers

Seismic isolation is an effective strategy to mitigate the risk of seismic damage in tunnels.However,the impact of surface-reflected seismic waves on the effectiveness of tunnel isolation layers remains under explored.In this study,we employ the wave function expansion method to provide analytical solutions for the dynamic responses of linings in an elastic half-space and an infinite elastic space.By comparing the results of the two models,we investigate the seismic isolation effect of tunnel isolation layers induced by reflected seismic waves.Our findings reveal significant differences in the dynamic responses of the lining in the elastic half-space and the infinitely elastic space.Specifically,the dynamic stress concentration factor(DSCF)of the lining in the elastic half-space exhibits periodic fluctuations,influenced by the incident wave frequency and tunnel depth,while the DSCF in the infinitely elastic space remain stable.Overall,the seismic isolation application of the tunnel isolation layer is found to be less affected by surface-reflected seismic waves.Our results provide valuable insights for the design and assessment of the seismic isolation effect of tunnel isolation layers.

Jet formation and penetration performance of a double-layer charge liner with chemically-deposited tungsten as the inner liner

This paper proposes a type of double-layer charge liner fabricated using chemical vapor deposition(CVD)that has tungsten as its inner liner.The feasibility of this design was evaluated through penetration tests.Double-layer charge liners were fabricated by using CVD to deposit tungsten layers on the inner surfaces of pure T2 copper liners.The microstructures of the tungsten layers were analyzed using a scanning electron microscope(SEM).The feasibility analysis was carried out by pulsed X-rays,slug-retrieval test and static penetration tests.The shaped charge jet forming and penetration law of inner tungsten-coated double-layer liner were studied by numerical simulation method.The results showed that the double-layer liners could form well-shaped jets.The errors between the X-ray test results and the numerical results were within 11.07%.A slug-retrieval test was found that the retrieved slug was similar to a numerically simulated slug.Compared with the traditional pure copper shaped charge jet,the penetration depth of the double-layer shaped charge liner increased by 11.4% and>10.8% respectively.In summary,the test results are good,and the numerical simulation is in good agreement with the test,which verified the feasibility of using the CVD method to fabricate double-layer charge liners with a high-density and high-strength refractory metal as the inner liner.

Formation behaviors of rod-like reactive shaped charge penetrator and their effects on damage capability

Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical simulations.The pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are used.Three types of sphericalsegment aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with Cu contents of 0%,46.6%,and 66%are fabricated and tested.The experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect,but the tail skirts disappear over time.Moreover,rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP impact.From simulation analysis,the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning,forming a leading reactive penetrator and a following chemical energy cluster.The unique formation structure determines the damage modes of the aluminum plate and the steel plate.Further analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu content.With increasing Cu content,the velocity,activation extent,and reaction extent of Al-PTFE-Cu RRSCP decrease,which contribute to elongation and alleviate the negative effects of chemical reactions on elongation,significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate penetration.However,the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.