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Plastic strain of railway ballast subjected to various fouling conditions was determined under simulated traffic loading through testing with large-scale cyclic triaxial equipment. Mechanisms by which fouling material affects the plastic strain of railway ballast were investigated. Fouling content (% by weight of particles 3%) resulted in larger accumulation of plastic strain in fouled ballast under traffic loading. Soil-suction tests showed that plastic strain of fouled ballast with suction >2000 kPa is similar to that of clean ballast, regardless of fouling and moisture content. For noncohesive fouling material (mineral and coal fouling), plastic strain is affected by fouling and moisture; therefore, a noncohesive fouling index (NFI) is proposed. In cohesive (clay) fouling, plastic strain is controlled by moisture and fouling content, as well as compositional characteristics of the cohesive fouling material, primarily represented by Atterberg limits and % mass Key words: railway ballast, fouling, plastic deformation, cyclic loading. La deformation plastique d'un ballast de chemin de fer soumis a differentes conditions de colmatage a ete determinee par la simulation de charges de trafic avec des essais triaxiaux cycliques a grande echelle. Les mecanismes par lesquels le materiel de colmatage affecte la deformation plastique du ballast de chemin de fer ont ete etudies. Le contenu colmate (% massique de particules < 12 mm) a augmente la deformation plastique du ballast en contaminant les points de contact entre les particules de ballast. L'augmentation de l'humidite (> 3%) a cause une plus grande accumulation de deformation plastique dans les ballasts colmates soumis a des charges de trafic. Des essais de succion ont demontre que la deformation plastique des ballasts colmates avec des succions > 2000 kPa est semblable a celle des ballasts propres, peu importe le contenu colmate et la teneur en humidite. Pour les materiaux de colmatage non cohesifs (colmatage mineral et charbon), la deformation plastique est affectee par le colmatage et l'humidite; alors un indice de colmatage non cohesif (ICN) est propose. Dans le cas de colmatage cohesif (argile), la deformation plastique est controlee par le contenu en humidite et colmate, de meme que par les caracteristiques de composition du materiel de colmatage cohesif, principalement represente par les limites d'Atterberg et le % massique inferieur a 0,075 mm. Un indice de colmatage cohesif (ICC) est propose pour caracteriser la deformation de ballasts colmates cohesifs. [Traduit par la Redaction] Mots-cles: ballast de chemin de fer, colmatage, deformation plastique, charge cyclique., Introduction A major concern facing the freight rail industry in the US is increasing maintenance costs due to heavier freight loads (Lee 2009). Maintenance operations for ballast in the US [...]

To reduce the use of natural aggregates commonly used in base layers, constructing recycled aggregate base (RAB) layers has gained popularity. However, in the literature, there is limited information about the engineering properties of recycled concrete aggregate (RCA) materials with different gradations and the blends of RCA and recycled asphalt pavement (RAP) materials. There is also a lack of practice in using a mechanistic-empirical (ME) design method to optimize RAB layer thicknesses. In this study, several full-scale test cells were built with RAB and natural aggregate base layers, and the physical and engineering properties of the base layer aggregates were determined in the laboratory. For long-term performance evaluation of the cells built in the field, falling weight deflectometer (FWD) tests were performed, rutting measurements were taken, and soil temperature was monitored over a period of two years. An ME design procedure was used to optimize RAB layer thicknesses. [ABSTRACT FROM AUTHOR]

Recycled asphalt shingles (RAS) mixed with granular materials or cementitiously stabilized to control their otherwise high compressibility provide a viable lightweight structural fill material in highway embankments or backfill behind retaining structures. In this research, deviator creep response of RAS mixed with bottom ash (BA) or stabilized with self- cementing fly ash (FA) was investigated. Systematic constant stress consolidated-drained triaxial tests were conducted on compacted RAS- BA and RAS-FA mixtures at ranges of confining pressures, deviator stresses, and temperatures expected in the field. Results showed that both compacted RAS-BA and RAS-FA mixtures represent classic creep response similar to soils. Creep rupture was observed at deviator stresses higher than 80% of deviator stress at failure. To prevent creep rupture, mobilized shear strength in the design of side slopes of highway embankments containing RAS should be limited to 80% of deviator stress at failure. Creep rate is affected by confining pressures. At a given stress level, the creep rate decreased and the time to creep rupture increased with increasing confining pressure. Temperature change also affects the creep strain and strain rate of compacted RAS-BA and RAS-FA mixtures. The strain rate of the compacted RAS-BA mixture exponentially increased with temperature. However, thermal pre-loading at summer field temperatures significantly reduced the strain rate of the compacted RAS-BA mixture from 64 x [10.sup.-6]%/min to 3.6 x [10.sup.-6]%/min and that of the RAS-FA mixture from 190 x [10.sup.-6]%/min to 6.9 x [10.sup.-6]%/min. To minimize creep strain and strain rate of structural fill materials containing RAS, construction is recommended during warm seasons. Creep models were developed to evaluate the time-dependent deformation of embankments constructed with RAS mixed with granular materials or stabilized with self-cementing fly ash. Key words: recycled asphalt shingle, creep, bottom ash, fly ash, temperature, structural fill. Des bardeaux d'asphalte recycles (BAR), melanges a des materiaux granulaires ou stabilises avec des materiaux cimentaires pour controler leur forte compressibilite, permettent d'obtenir un materiau de remplissage structural leger et viable pour des applications de remblai d'autoroute ou derriere des structures de soutenement. Dans ces travaux de recherche, le comportement en fluage deviateur de BAR melanges avec des cendres de grille (CG) ou stabilises avec des cendres volantes (CV) auto-cimentees a ete etudie. Des essais triaxiaux consolides-draines a contrainte constante ont ete realises systematiquement sur des melanges BAR-CG et BAR-CV compactes, sous differentes pressions de confinement, contraintes deviatrices, et temperatures attendues sur le terrain. Les resultats demontrent que les deux melanges compactes BAR-CG et BAR-CV representent des reponses classiques de fluage, de facon similaire aux sols. La rupture en fluage a ete observee a des contraintes deviatrices superieures a 80% de la contrainte deviatrice a la rupture. Pour prevenir la rupture en fluage, la resistance au cisaillement mobilisee dans la conception de pentes sur les cotes des remblais d'autoroute contenant des BAR devrait etre limitee a 80% de la contrainte deviatrice a la rupture. Le taux de fluage est affecte par les pressions de confinement. Pour un niveau de contrainte donne, le taux de fluage diminue et le temps avant la rupture en fluage augmente avec l'augmentation de la pression de confinement. Les changements de temperature affectent aussi la deformation en fluage et le taux de deformation des melanges BAR-CG et BAR-CV compactes. Le taux de deformation du melange BAR-CG augmente de facon exponentielle avec la temperature. Cependant, le pre-chargement thermal durant les temperatures estivales sur le terrain reduit significativement le taux de deformation du melange BAR-CG compacte de 64 x [10.sup.-6] a 3,6 x [10.sup.-6]%/min, et celui du melange BAR-CV de 190 x [10.sup.-6] a 6,9 x [10.sup.-6]%/min. Pour minimiser la deformation en fluage et le taux de fluage de materiaux de remplissage structuraux contenant des BRA, la construction durant les saisons chaudes est recommandee. Des modeles de fluage ont ete developpes pour evaluer la deformation dependante du temps de remblais construits avec des BAR melanges a des materiaux granulaires ou stabilises avec des cendres volantes auto-cimentees. [Traduit par la Redaction] Mots-cles: bardeaux d'asphalte recycles, fluage, cendre de grille, cendre volante, temperature, remplissage structural., Introduction Recycled materials and byproducts are increasingly introduced as aggregate to enhance the sustainability of roadway construction by reducing energy and natural resource consumption as well as greenhouse gas (GHG) [...]

An assessment of state-of-the-practice at five full-scale North American landfills operating as bioreactors is presented in this two-paper set. This paper focuses on effectiveness of liners and leachate collection systems, leachate generation rates, leachate recirculation practices and rates, effectiveness in moistening the waste, and settlement of the waste over time. Except in one case, the liner and leachate collection systems at the bioreactor landfills were similar to those used for landfills operated conventionally. Leachate generation rates increased approximately linearly with recirculation rate, but in all cases, the leachate generation rate was DOI: 10.1061/(ASCE)EE.1943-7870.0000219 CE Database subject headings: Landfills; Reactors; Solid wastes; Liners; Hydrology; Settlement. Author keywords: Landfills; Bioreactor: Solid waste; Liners; Leachate: Hydrology; Settlement.

Column tests were conducted to evaluate two treatment strategies for reducing and stabilizing hexavalent chromium, Cr(VI), in chromium ore processing residue (COPR): permeation with a FeS[O.sub.4]-[H.sub.2]S[O.sub.4] solution and blending with a cationic polysulfide reagent (Ca[S.sub.x]). Cr(VI) leached at concentrations exceeding 50 mg/L from untreated COPR permeated with synthetic groundwater for > 20 pore volumes of flow (PVF), and concentrations of Cr(VI) in the solid phase remained high (6,600 mg/kg). Permeation with solutions containing FeS[O.sub.4]-[H.sub.2]S[O.sub.4] eliminated Cr(VI) from the effluent after initial, elevated leaching of Cr(VI) (100-1,500 mg/kg); however, high solid-phase concentrations of Cr(VI) remained in the column residuals (> 1,300 mg/kg). COPR treated with Ca[S.sub.x] leached Cr at < 0.33 mg/L for 23.5 PVF and had solid-phase concentrations of Cr(VI) < 10 mg/kg, although mineralogical analyses of treated solids showed potential chromate-containing mineral phases. Mineralogical analyses showed that precipitation and cementation occurred in the pore space of the COPR permeated with FeS[O.sub.4]-[H.sub.2]S[O.sub.4], initially lowering the hydraulic conductivity > two orders of magnitude. However, acid dissolution channels eventually formed, resulting in preferential flow. COPR permeated with FeS[O.sub.4]-[H.sub.2]S[O.sub.4] contained less brownmillerite and Cr(VI)-bearing hydrocalumite and hydrogarnet relative to untreated COPR. For COPR treated with Ca[S.sub.x], S encapsulated the subparticles of COPR with some micropore penetration, suggesting permanence of excess reductant after leaching with 23.5 PVF of synthetic rainwater. CE Database subject headings: Acids; Chemical treatment; Expansive soils; Industrial wastes; Metals; Stabilization; Sulfides.

This study evaluated the effects of physical characteristics and geologic factors on the shear strength of compacted sands from Wisconsin that are used as granular backfill for mechanically stabilized earth walls and reinforced soil slopes. Physical properties and shear strength were determined for 30 compacted sands collected from a broad range of geological deposits. Relationships between strength/deformation behavior, geologic origin, and physical properties were used to categorize the sands into four friction angle groups. Sands with the lowest friction angle are derived from weathering of underlying sandstones, and tend to be medium-fine, well-rounded, and poorly graded sands. Sands with the highest friction angle are from recent glacial activity and tend to be coarser grained, well-graded, and/or angular sands. A multivariate regression model was developed that can be used to predict friction angle ([PHI]') of compacted sands from comparable geological origins based on effective particle size ([D.sub.10]), maximum dry unit weight ([[gamma].sub.dmax]), and Krumbein roundness ([R.sub.s]). CE Database subject headings: Sand; Friction; Displacement; Mineralogy; Backfills; Slopes.

Direct shear tests were conducted on 30 sand backfill materials having gravel contents ranging from 0% to 30% in a 64 mm square small-scale direct shear (SSDS) box and a 305 mm square large-scale direct shear (LSDS) box. The objectives were to compare the shearing behavior of a broad range of natural sand backfill materials tested in SSDS and LSDS and to determine if the same friction angle (φ') is obtained in SSDS and LSDS when the natural backfill material contains gravel. Triaxial compression (TC) tests were also conducted on four of the backfill materials for comparison with the SSDS and LSDS tests. Specimens tested in SSDS and TC included only material passing the No. 4 sieve (P4). Test specimens in LSDS included the P4 material as well as material retained on the No. 4 sieve (R4), to a maximum particle diameter of 25.4 mm. Friction angles corresponding to peak strength (φ') measured in SSDS and LSDS differed by no more than 4° for a given sand backfill, and in most cases were within 2°. The friction angles also were unaffected by removal of the R4 material. Repeatability tests showed that statistically similar failure envelopes (p-value = 0.98) are obtained in SSDS and LSDS, and that highly repeatable friction angles (φ') are obtained using the SSDS (φ' ± 0.25°) and the LSDS (φ' ± 0.45°) methods. No statistically significant difference was found among the failure envelopes measured in SSDS, LSDS, and TC, suggesting that φ' for clean sand backfill with less than 30% gravel can be measured with similar accuracy using any of the three test methods. Key words: : direct shear box test, angle of internal friction, sand, triaxial compression, shear strength, backfill, gravel, mechanically stabilized earth. Des essais de cisaillement direct ont ete realises sur 30 materiaux de remblai ayant des teneurs en gravier s'etendant de 0 % a 30 % dans une boite de cisaillement direct << SSDS >> de petite echelle de 64 mm carree et une boite a cisaillement direct a grande echelle << LSDS >> de 305 mm carree. Les sableux objectifs etaient de comparer le comportement en cisaillement d'une large plage de materiaux sableux naturels de remblai testes dans des boites SSDS et LSDS.et de determiner si le meme angle de frottement (φ') est obtenu dans un SSDS et un LSDS lorsque le materiau de remblai naturel contient du gravier. On a aussi realise des essais de compression triaxiale << TC >> sur quatre des materiaux de remblai pour com paraison avec les essais SSDS et LSDS. Les specimens testes dans le SSDS et le TC incluaient seulement du materiau passant le No. 4 tamis (R4), jusqu'a une diametre maximum de particule de 25.4 mm. Les angles de frottement correspondant a la resistance de pic (φ') mesures dans le SSDS et le LSDS ne differaient de pas plus que 4[degre] pour un sable de remblai donne, et dans la plupart des cas ils etaient a l'interieur de 2[degre]. Les angles de frottement n'etaient aussi pas affectes par l'elimination du materiau R4. Les essais de repetitivite ont montre qu'on obtient des enveloppes de rupture statistiquement similaires (valeur de p = 0.98) dans le SSDS et le LSDS, et que des angles de frottement (φ') fortement repetitifs sont obtenus en utilisant la methode SSDS (φ' [+ ou -] 0.25[degre]) et la methode LSDS (phi]' [+ ou -] 0.45[degre]). On n'a pas trouve de differences statistiquement significatives entre les enveloppes de rupture mesurees dans le SSDS, le LSDS, et le TC, ce qui suggere que φ' pour le remblai de sable propre avec moins de 30 % de gravier peut etre mesure avec une precision similaire en utilisant n'importe laquelle des trois methodes d'essai. Mots-cles : essai a la boite de cisaillement direct, angle de frottement interne, sable, compression triaxiale, resistance au cisaillement, remblai, gravier, sol stabilise mecaniquement. [Traduit par la Redaction], Introduction The direct shear (DS) test is commonly used in commercial geotechnical laboratories in North America for testing granular materials used as backfill for mechanically stabilized earth (MSE) walls and [...]

Abstract: The ultimate parameter of interest in engineering design of compacted subgrades and support fills for highways, railroads, airfields, parking lots, and mat foundations is often the soil modulus. Modulus [...]

Alibey Dam is located near Istanbul in Turkey on the Alibey Stream, 4.5 km north of its point of confluence with Golden Horn, an ancient submerged river mouth. It was constructed as an earthfill dam over 30-m-thick soft valley sediments. Before the construction of the dam, field and laboratory tests were performed to determine the geotechnical characteristics of the foundation soils. During the construction and many years after the construction of the earthfill embankments, including the cofferdams and the intermediate fills, the response of the foundation soils was monitored by extensive field instrumentation generating a unique long-term (over 25 years) database. With proper instrumentation and careful monitoring of the collected data, field construction rates could be adjusted and the earth dam was safely constructed on the thick soft deposits. Approaches to settlement prediction were evaluated in a historical context, starting with the simplified one-dimensional approach available at the time of construction to more sophisticated analyses including the employment of modern numerical methods, in terms of the recorded data. Standard subsurface exploration and field testing supplemented with conventional laboratory testing provided the relevant material parameters that were used in the finite element method. The only exception to this was the overall hydraulic conductivity of the deposit, which controlled the rate of consolidation. Early field observations were used to assign the appropriate hydraulic conductivity. An elastoplastic soil model in a coupled analysis of consolidation was employed in the analysis that yielded realistic predictions of field behavior in response to the complex construction history. The accurate prediction and monitoring of the behavior of soft and thick soil layers subjected to staged construction, as in the case of Alibey Dam, is very important for planning of the construction as well as the expected behavior after construction. CE Database subject headings: Dam construction; Dam foundations; Clays; Soft soils; Turkey.

Abstract: A three-compartment model was developed for simulating cation transport in bentonitic barrier layers that incorporates diffusion-controlled cation exchange among the mobile intergranular water (bulk pore water), immobile interparticle and [...]

The objective of this study was to evaluate the effectiveness of self-cementing fly ashes derived from combustion of sub-bituminous coal at electric power plants for stabilization of soft fine-grained soils. California bearing ratio (CBR) and resilient modulus ([M.sub.r]) tests were conducted on mixtures prepared with seven soft fine-grained soils (six inorganic soils and one organic soil) and four fly ashes. The soils were selected to represent a relatively broad range of plasticity, with plasticity indices ranging between 15 and 38. Two of the fly ashes are high quality Class C ashes (per ASTM C 618) that are normally used in Portland cement concrete. The other ashes are off-specification ashes, meaning they do not meet the Class C or Class F criteria in ASTM C 618. Tests were conducted on soils and soil-fly ash mixtures prepared at optimum water content (a standardized condition), 7% wet of optimum water content (representative of the typical in situ condition in Wisconsin), and 9-18% wet of optimum water content (representative of a very wet in situ condition). Addition of fly ash resulted in appreciable increases in the CBR and [M.sub.r] of the inorganic soils. For water contents 7% wet of optimum, CBRs of the soils alone ranged between 1 and 5. Addition of 10% fly ash resulted in CBRs ranging between 8 and 17 and 18% fly ash resulted in CBRs between 15 and 31. Similarly, [M.sub.r] of the soil alone ranged between 3 and 15 MPa at 7% wet of optimum, whereas addition of 10% fly ash resulted in [M.sub.r] between 12 and 60 MPa and 18% fly ash resulted in [M.sub.r] between 51 and 106 MPa. In contrast, except for one fly ash, addition of fly ash generally had little effect on CBR or [M.sub.r] of the organic soil. CE Database subject headings: Fine-grained soils; Fly ash; California bearing ratio; Soil stabilization; Recycling; Sustainable development; Subgrades.

Three index properties (liquid limit, sedimentation volume, and swell index) of two sodium bentonites from geosynthetic clay liners (GCLs) are correlated with the hydraulic conductivity (k) of the same GCLs to evaluate the suitability of index properties for evaluating chemical compatibility. Deionized water (DIW) and calcium chloride (Ca[C1.sub.2]) solutions were used for hydration (index tests) and permeation (hydraulic conductivity tests). In general, increasing the Ca[Cl.sub.2] concentration caused each index properly to decrease and the hydraulic conductivity to increase relative to values obtained with DIW, with the strongest correlations obtained with the liquid limit. The correspondence between index properties and hydraulic conductivity differed by index property, the quality of the bentonite, and the effective stress applied during the hydraulic conductivity test. Thus, correlations used for compatibility assessments are specific to the bentonite in the GCL and the stress conditions being applied. Results of the study also show that appreciable changes in hydraulic conductivity can occur with little or no change in index properties and that the greatest changes in index properties may correspond to conditions causing low or modest changes in hydraulic conductivity. However, in this study, a critical threshold existed for each index property, beyond which further decreases in an index property correlated with substantial increases (>> 10 x) in hydraulic conductivity. DOI: 10.1061/(ASCE) 1090-0241 (2005) 131:11 (1319) CE Database subject headings: Atterberg limits; Bentonite; Clay liners; Geosynthetics; Hydraulic conductivity; Inorganic chemicals: Sedimentation; Swelling.

Filtration performance of nonwoven geotextiles strongly depends on pore opening constriction size, i.e., the minimum opening size of flow channels across the geotextile. Currently available methods of pore opening characterizations do not provide accurate information about the constriction size. This paper presents the constriction size distributions of eleven nonwoven geotextiles commonly used as filters based on a probabilistic approach coupled with image analysis, named constriction size (CONS). The image analysis method was developed using mathematical morphology operations. Randomness in the structure of geotextile media was modeled using Markov chain processes. Two characteristic constriction sizes, [C.sub.95] and [C.sub.50] were determined and compared with the available results from laboratory tests, theoretical equations, and manufacturer's reported apparent opening sizes. The CONS-based [C.sub.95] constriction size was comparable to [C.sub.95] determined using the bubble point test. On the other hand, the CONS-based [C.sub.95] was consistently lower than the manufacturer's reported apparent opening size, which is typically determined on the basis of the dry sieving test. Similarly, the CONS-based [C.sub.95], was highly comparable with the value suggested by a theoretical equation. The observed differences in the constriction sizes determined by CONS versus the available physical tests may be reflective of the nature and indirectness of the physical tests rather than inaccuracies associated with CONS, which is based on direct observation of pore openings. CE Database subject headings: Geosynthetics; Digital techniques; Imaging techniques; Pore size distribution: Markov chains.

The influence of multispecies inorganic solutions on swelling and hydraulic conductivity of non-prehydrated geosynthetic clay liners (GCLs) containing sodium bentonite was examined. Ionic strength and the relative abundance of monovalent and divalent cations (RMD) in the permeant solution were found to influence swell of the bentonite, and the hydraulic conductivity of GCLs. Swell is directly related to RMD and inversely related to ionic strength, whereas hydraulic conductivity is directly related to ionic strength and inversely related to RMD. RMD has a greater influence for solutions with low ionic strength (e.g., 0.05 M), whereas concentration effects dominate at high ionic strength (e.g., 0.5 M). No discernable effect of cation species of similar valence was observed in the swell or hydraulic conductivity data for test solutions with similar ionic strength and RMD. A strong relationship between hydraulic conductivity and free swell was found, but the relationship must be defined empirically for a particular bentonite. A regression model relating hydraulic conductivity of the GCL to ionic strength and RMD of the permeant solution was developed. Predictions made with the model indicate that high hydraulic conductivities (i.e., > [10.sup.7] cm/s) are not likely for GCLs in base liners in many solid waste containment facilities. However, for wastes with stronger leachates or leachates dominated by polyvalent cations, high hydraulic conductivities may occur. CE Database subject headings: Hydraulic conductivity; Swelling; Inorganic chemicals; Clay liners; Bentonite.

Scrap tire disposal is a problem of growing concern. One solution to this problem is innovative methods for the reuse and recycling of scrap tires. Based on batch isotherm tests, scrap tire chips have been identified to be good sorbents of volatile organic compounds (VOCs) and could be used as leachate drainage layer material in solid waste landfills and in other similar applications. To demonstrate the effects of tire chips on the leachate they come in contact with in a drainage layer over a liner, large-scale tank tests simulating the drainage layer and the clay liner and also field tests were performed. Two cells were constructed in a landfill: one with scrap tire chips and the other with gravel leachate collection layer. According to the results of the large-scale tank tests and field tests, shredded tire chips have a significantly positive impact on the quality of the leachate with which they come in contact. The use of scrap tires in landfills would reduce the magnitude of the current tire disposal problem (a 1 ha landfill requires approximately 300,000 tires to fill 0.3 m of a leachate collection layer) and convert one waste into a beneficial construction material and simultaneously mitigate the problem of VOC transport from through landfill liners. DOI: 10.1061/(ASCE)0733-9372(2004)130:7(824) CE Database subject headings: Clay liners; Columns; Sorption; Volatile organic chemicals; Drainage; Tires; Recycling; Landfills.

Determining the deformation response of geosynthetics under load is important in developing an in-depth understanding of the engineering behavior of these materials. Current strain determination methods employed as part of tensile tests mostly assume that the strain is uniform throughout the specimen and, hence, are incapable of determining local strains. Geosynthetics have occasionally been instrumented with strain gauges and extensometers; however, these direct contact methods have limitations in fully defining strain distributions in a test specimen. Recent technological advancements in image analysis offer great potential for a more accurate and noncontact method of determining strains. An image-based particle tracking method was used to define the strain distribution in various geosynthetics during wide-width tensile testing. The method used a block-based matching algorithm functioning under LABVIEW. The measured gross strain values were compared to those determined from strain gauges and extensometers. The strain values determined by these methods were comparable to the image-based ones, and the absolute value of the difference was less than 10% for the geosynthetics tested. Furthermore, the image-based analysis was effective in also determining the local strains. CE Database subject headings: Image analysis; Strain distribution; Deformation; Geosynthetics.