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Microstructure showing the involvement of the fine and coarse grains in the soil skeleton is evaluated. Incremental loading tests using a stress-dependent permeameter are conducted on the mixtures of poorly graded sand and nonplastic fines originating from tailings. The results are compared with the published data of various tailings. It is shown that increasing the fines content from 0% to 100%, the involvement of the fine and coarse components of soil skeleton can be classified into four categories: no fines involvement (40% fines). At the same consolidation stress, the void ratio, e, rapidly decreases for fines less than 30%, then almost remains constant between 30% and 50% fines, and gradually increases for fines exceeding 50%. The hydraulic conductivity, k, decreases more than 20-fold as the fines content increases from 12% to 50%, then remains constant. k is proportional to [[[e.sup.3]/(1 + e)].sub.A] and inversely proportional to [S.sup.2], where A is a factor describing the effect of particle angularity and S is the specific surface. Finally, the influence of fines content on the seepage- induced internal stability is discussed. Key words: soil skeleton, sands, silts, nonplastic fines, tailings, compressibility, hydraulic conductivity, angularity, specific surface. La microstructure montrant l'implication des grains fins et grossiers dans le squelette du sol est evaluee. Des essais de charge incrementielle a l'aide d'un permeametre dependant de la contrainte sont realises sur des melanges de sable mal calibre et de fines non plastiques provenant de residus. Les resultats sont compares aux donnees publiees de divers residus. Il est demontre qu'en augmentant la teneur en fines de 0 a 100 %, l'implication des composantes fines et grossieres du squelette du sol peut etre classee en quatre categories : aucune implication des fines ( 40 % de fines). Pour une meme contrainte de consolidation, le taux de vide, e, diminue rapidement pour les fines inferieures a 30 %, puis reste presque constant entre 30 et 50 % de fines, et augmente progressivement pour les fines superieures a 50 %. La conductivite hydraulique, k, est divisee par plus de 20 lorsque la teneur en fines passe de 12 a 50 %, puis reste constante. k est proportionnel a [[[e.sup.3]/(1 + e)].sup.A] et inversement proportionnel a [S.sup.2], ou A est un facteur decrivant l'effet de l'angularite des particules et S est la surface specifique. Enfin, l'influence de la teneur en fines sur la stabilite interne induite par le suintement est discutee. [Traduit par la Redaction] Mots-cles : squelette du sol, sables, limons, fines nonplastiques, residus, compressibilite, conductivite hydraulique, angularite, surface specifique., Introduction Compressibility and permeability are two of the most important engineering properties of soil because of their influence on rate of consolidation, settlement, seepage, and stability. These two soil parameters [...]

Two geosynthetic clay liners (GCLs) reported to have experienced significant shrinkage at other locations are examined on both a 3H:1V south-facing slope and a relatively flat base on a silty sand. The GCLs were overlapped by 300 mm with 400 g/m of supplemental bentonite and covered by a black 1.5 mm high-density polyethylene (HDPE) geomembrane to form a composite liner that was left exposed in a full-scale field test embankment for a period of almost 5 years. It is shown that despite the relatively uniform exposure conditions, shrinkage is highly variable with a maximum shrinkage of GCL A being 165 mm on the slope and 415 mm on the base while GCL B shrunk by up to 75 mm on the side slope and only up to 25 mm on the base. The dominant role played by variable overlap stick and heterogeneity to the locations where the overlaps are re-wetted are discussed. Based on this study of shrinkage and a related study of downslope erosion at the same site, it is concluded that neither GCLs A nor B should be left in exposed composite liners when they can be subjected to thermal cycles that can lead to hydration and dehydration of the GCL. Key words: geosynthetics, composite liner, geosynthetic clay liner, overlap, shrinkage. Deux doublures d'argile geosynthetique (GCL) qui ont connu un retrecissement significatif a differents endroits sont examines sur une pente orientee au sud de 3H:1V et d'une base relativement plate sur un sable limoneux. Les GCL ont ete chevauches de 300 mm avec 400 g/m de bentonite supplementaires et recouverts d'une geomembrane en polyethylene haute densite (HDPE) noire de 1,5 mm pour former une doublure composite qui a ete laissee exposee dans un talus d'essai a grande echelle pour une periode de pres de 5 annees. Il a ete demontre que, malgre les conditions d'exposition relativement uniformes, le retrecissement est tres variable avec un retrecissement maximal de la GCL de 165 mm sur la pente et de 415 mm sur la base tandis que la GCL B est retrecie jusqu'a 75 mm sur la pente laterale et seulement jusqu'a 25 mm sur la base. Le role dominant joue par l'adhesion du chevauchement variable et aleatoire aux endroits ou les chevauchements sont a nouveau en contact avec le produit est discute. Sur la base de cette etude du retrecissement et d'une etude connexe de l'erosion descendante sur le meme site, on conclut que ni les GCL A et ni B ne devraient etre laissees dans des revetements plastiques exposes lorsqu'ils peuvent etre soumis a des cycles thermiques pouvant entrainer l'hydratation et la deshydratation de la GCL. [Traduit par la Redaction] Mots-cles: geosynthetiques, doublure composite, revetement d'argile geosynthetique, chevauchement, retrecissement., Introduction Composite liners comprised of a geomembrane over a geosynthetic clay liner (GCL) are extensively used in landfills and increasingly in mining applications (Shackelford et al. 2000; Bouazza 2002; Rowe [...]

Long-span metal culverts have been used for almost 50 years as an economical alternative to short-span bridges. Current design methods are based on two-dimensional finite element analysis using beam theory to represent the structure, or three-dimensional analysis employing orthotropic shell theory. However, neither analysis has been used to investigate the most critical position for trucks at the surface of long-span metal culverts. This paper shows results of three-dimensional finite element analysis, employing orthotropic shell theory and explicitly modeling the geometry of corrugated plates for a specific box culvert tested using a fully loaded dump truck. The analysis was then extended to study the effect of truck position on the response of long-span box and arch culverts. The finite element models, employing orthotropic shell theory and explicitly modeling the geometry of corrugated plates, successfully produced the behaviour of the culvert under truck loading for different truck positions. Culvert deformations were calculated within 7%-13% of the measured values at different locations. The bending moment at the crown was within 4%-17% of the values calculated using the measured strains. If three-dimensional finite element analysis is used to design these culverts, two design trucks should be considered (current design considers a single design truck). The highest moment or thrust is obtained when the truck tandem axles are located above the crown of the culvert. Key words: long-span culverts, truck-induced stresses, three-dimensional finite element analysis, full-scale tests. Les ponceaux metalliques a grande portee sont utilises depuis pres de 50 ans comme alternative economique aux ponts a faible portee. Les methodes de conception actuelles sont basees sur l'analyse par elements finis dans laquelle la theorie des poutres represente la structure, ou sur une analyse tridimensionnelle utilisant la theorie de l'enveloppe orthotropique. Cependant, aucune de ces analyses n'ont ete utilisees pour evaluer la position la plus critique des camions a la surface des ponceaux metalliques a grande portee. Cet article presente les resultats d'une analyse tridimensionnelle par elements finis qui utilise la theorie de l'enveloppe orthotropique et qui modelise explicitement la geometrie de toles ondulees pour un ponceau rectangulaire specifique teste avec un camion a benne completement charge. L'analyse a ensuite ete poursuivie pour etudier les effets de la position du camion sur le comportement des ponceaux rectangulaires a grande portee et des ponceaux a arches. Les modeles par elements finis qui utilisent la theorie de l'enveloppe orthotropique et qui modelisent explicitement la geometrie de toles ondulees ont permis de reproduire avec succes le comportement du ponceau pour differentes positions des camions charges. Les deformations du ponceau calculees etaient entre 7 et 13 % des valeurs mesurees a differents emplacements. Le moment de torsion a la crete etait entre 4 et 17 % des valeurs calculees a partir des deformations mesurees. Si l'analyse tridimensionnelle par elements finis est utilisee pour la conception de ce type de ponceau, deux camions conceptuels devraient etre consideres (l'approche actuelle considere un seul camion). Le moment, ou la poussee, le plus eleve est obtenu lorsque les essieux tandems sont situes au-dessus de la crete du ponceau. [Traduit par la Redaction] Mots-cles: ponceaux a grande portee, sollicitations par camions, analyse tridimensionnelle par elements finis, essais a l'echelle reelle., Introduction Long-span metal culverts may be an economical alternative to typical short-span concrete or steel stringer bridges (spans less than 8 m). They have gained general acceptance for use under [...]

Two 381 mm (15 in. nominal) diameter fiber reinforced cement pipes have been tested under embankment loading conditions to study pipe response in both low stiffness, fine grained backfill, and a high stiffness graded granular backfill. Pipe deformations and strains were measured and interpreted to provide insight into the effect of soil backfill on the deformations and moments that develop. Not surprisingly, the use of silty clay backfill resulted in greater pipe deflections while the stiffer granular backfill lead to greater load transfer to the surrounding ground. Calculations using elastic soil-pipe interaction theory were effective in estimating the observed changes in pipe diameter at typical service loads (overburden pressures of 100 kPa. i.e., 14.4 psi in the lower stiffness backfill and 200 kPa, i.e., 28.8 psi in the high stiffness backfill). Measured strain distributions show that the fiber reinforced pipe exhibited ovaling response similar to that seen for flexible and semiflexible pipes. As expected, tensile strains were observed on the outer surface at the springlines and the inner surface at the crown. Strains observed at the haunch were negligible, indicating that the bending moments within the pipe have conventional 'hourglass' distribution, with negligible moments at shoulders and haunches. Differences in strain measured at the inner and outer surfaces were used with the elastic pipe modulus to calculate the experimental bending moments. Comparisons of those experimental bending moments with the bending moment calculated for a rigid pipe indicate that these FRC pipe structures are semirigid so that moments are reduced as a result of support provided by the surrounding soil. A design expression for moment arching factor (MAF or moment divided by the rigid pipe moments) developed in an earlier paper was found to provide reasonable estimates for the experimental moment values. Moment estimated using the design soil moduli of McGrath and MAF provide moment values that are reasonable and conservative relative to those that were observed. DOI: 10.1061/(ASCE)GT.1943-5606.0000142 CE Database subject headings: Culverts; Underground structures: Infrastructure; Fiber reinforced materials; Cement; Soil-pipe interactions; Bending.