bluuebunny/crossref_metadata_2025 huggingface dataset:
OXYGEN CONSUMPTION AND AMMONIA EXCRETION OF THE ANTARCTIC AMPHIPOD Bovallia gigantea PFEFFER, 1888, AT DIFFERENT TEMPERATURES AND SALINITIES
Authors: Gomes Vicente , Passos Maria José de Arruda Campos Rocha , Rocha Arthur José da Silva , Santos Thais da Cruz Alves dos , Hasue Fabio Matsu , Ngan Phan Van
Published: October 2014

The energy budget of Antarctic stenothermic and/or stenohaline ectotherms is modulated by variations of temperature and salinity. The joint effects of these latter on polar organisms have been but little studied. Data on this subject are of great importance for an understanding of the energy demand of Antarctic animals such as amphipods, especially when considering their ecological importance and the possible impacts of global changes. Experiments were carried out at the Brazilian Antarctic Station "Comandante Ferraz" under controlled conditions. Specimens of Bovallia gigantea were collected in Admiralty Bay and acclimated to temperatures of 0ºC; 2.5ºC and 5ºC and to salinities of 35, 30 and 25. Thirty measurements were taken for each of the nine possible combinations of the three temperatures and the three salinities. Metabolic rates were assessed based on oxygen consumption and total ammonia nitrogenous excretion in sealed respirometers. At 0ºC and 2.5ºC, the metabolic rates of the animals that were acclimated to salinities of 30 or 35 were similar, indicating a possible mechanism of metabolic independence of temperature. However, the metabolic rates were always higher at 5.0ºC. The effects of temperature on oxygen consumption and on ammonia excretion rates were intensified by lower salinities. Individuals of B gigantea have a temperature-independent metabolic rate within a narrow temperature window that can be modified in accordance with salinity.
POPULATION BIOLOGY OF SEABOB-SHRIMP Xiphopenaeus kroyeri (Heller, 1862) CAPTURED ON THE SOUTH COAST OF PERNAMBUCO STATE, NORTHEASTERN BRAZIL
Authors: Lopes Danilo Francisco Corrêa , Silva Emanuell Felipe Beserra da , Peixoto Silvio Ricardo Maurano , Frédou Flavia Lucena
Published: October 2014

This paper aims to describe the population dynamics and to evaluate the stock of the seabob-shrimp Xiphopenaeus kroyeri on the coast of Pernambuco. Sampling was carried out between August/2011 and July/2012 in Sirinhaém, southern coast of Pernambuco. A total of 1201 individuals were analyzed, 673 females and 528 males. Total length (Lt) of females varied from 4.5 to 13.5 cm while the Lt of males ranged between 4.0 and 11.0 cm. The relationship between the Lt and carapace length and Lt and total weight showed negative allometry (males, females and pooled sexes). The slope of the curve "b" was statistically different between males and females for both relationships. Females mature with 8.90 cm. Asymptotic length L∞ was lower for males than for females (12.26 to 14.79 and 10.72 to 11.5 cm, respectively), K was similar between sexes (1.00-2.04 and 1.00-2.63 cm/year-1 respectively) as well as the longevity and size at 1st capture (1.50 to 1.97) years and 7.9 to 8.9 cm for males and females, respectively). The results indicate that X. kroyeri in the region is not overexploited for males, however considering females and pooled sexes the stock is near to being fully exploited.
Variabilidade espacial da estabilidade de agregados e estoque de carbono em Cambissolo e Argissolo
Authors: Alho Leandro Coutinho , Campos Milton César Costa , Silva Douglas Marcelo Pinheiro da , Mantovanelli Bruno Campos , Souza Zigomar Menezes de
Published: October 2014

O avanço de atividades agropecuárias, sem considerar as condições estruturais do solo, finda no detrimento destes ambientes. Este trabalho objetivou avaliar a variabilidade espacial da estabilidade de agregados, densidade do solo, carbono orgânico total (COT) e estoque de carbono de áreas de campo natural e floresta, na região de Humaitá (AM). Os solos foram amostrados nos pontos de cruzamento de uma malha de 70 m x 70 m, em intervalos regulares de 10 m, às profundidades de 0,0-0,05 m; 0,05-0,10 m; e 0,10-0,20 m, totalizando 64 amostras por profundidade. Os resultados da análise geoestatística mostraram dependência espacial dos atributos avaliados. Os menores alcances foram decorrentes das constantes variações na forma do relevo da área de campo natural. Os valores médios respectivos do índice de estabilidade diâmetro médio ponderado (DMP) e COT, em torno de 3,0 mm e 29,0 g kg-1 da camada superficial, similares aos das áreas de campo natural e floresta, confirmam a correlação proporcional entre os teores de COT e o DMP. Todavia, os níveis de densidade do solo superiores a 1,40 kg dm-3 expressam a ineficiência das funções estruturais do solo da área de campo natural. Os valores de estoque de carbono, nas diferentes profundidades, mostraram-se mais favorecidos pelos teores de COT que em razão dos diferentes níveis de adensamento dos solos estudados.
Embriogênese somática em Agave sisalana Perrine: indução, caracterização anatômica e regeneração
Authors: Carneiro Fernando dos Santos , Queiroz Sandra Regina de Oliveira Domingos , Passos Adriana Rodrigues , Nascimento Marilza Neves do , Santos Keylla Souza dos
Published: October 2014

O sisal (Agave sisalana Perrine) é utilizado para a extração das fibras contidas em suas folhas, sendo a principal fibra dura produzida no mundo. Entretanto, tem sido observado um declínio dessa cultura, devido a uma doença causada pelo fungo de solo Aspergilus niger. A biotecnologia, em especial as técnicas de cultura de tecidos, representa uma alternativa viável para a propagação dessa espécie. Dentre essas técnicas, está a embriogênese somática e, nesse sentido, este estudo objetivou caracterizar a morfogênese in vitro, durante a embriogênese somática, em A. sisalana Perrine. Em todos os experimentos, utilizaram-se bulbilhos como explantes e meio de cultura MS½ acrescido de sacarose (30,0 g L-1), solidificado com ágar (7,0 g L-1) suplementado com diferentes concentrações de auxinas e citocininas. Os explantes formaram calos com aspectos compactos e semicompactos, evidenciando células embriogênicas que se converteram em embriões somáticos, com o uso de 2,4-D e BAP. Por meio das análises anatômicas, pôde-se observar embriões em estádios globular e torpedo e a não conexão com o calo mãe.
Divergência genética e índice de seleção via BLUP em acessos de algodoeiro para características tecnológicas da fibra
Authors: Resende Maria Aparecida Vilela de , Freitas Joelson André de , Lanza Marcelo Abreu , Resende Marcos Deon Vilela de , Azevedo Camila Ferreira
Published: October 2014

As características tecnológicas da fibra do algodoeiro são determinantes da qualidade de seus produtos e de sua remuneração. Este trabalho objetivou estimar a divergência genética entre acessos de algodoeiro e ordenar os melhores, com base em um índice de seleção combinando todas essas características de interesse. Foram avaliados 248 acessos de algodoeiro, empregando-se análise multivariada (distância de Mahalanobis e agrupamento de Tocher) e índice de seleção baseado em rank médio via metodologia de modelos mistos (REML/BLUP). A análise de agrupamento de Tocher permitiu a estruturação populacional dos acessos, resumindo-os em 14 grupos divergentes. As acurácias seletivas foram altas para todas as características avaliadas, variando de 0,89 a 0,94, indicando situação favorável à seleção. As correlações entre as seis variáveis apresentaram magnitudes moderadas a baixas, não sendo possível o melhoramento de uma característica, via seleção indireta, em outra. A seleção simultânea para as características de fibra, com base no índice de seleção de Mulamba e Mock, mostrou-se promissora. Os melhores acessos para as seis variáveis, simultaneamente, foram 4S180, C96480, Giza75, 196Lasani11, Brown Egyptian, Early Fluff 316, C268-80 e 207MG-82607.
Early Ordovician (Skullrockian) Trilobites of the Antiklinalbugt Formation, Northeast Greenland, and their Biostratigraphic Significance
Authors: McCobb Lucy M. E. , Boyce W. Douglas , Knight Ian , Stouge Svend
Published: October 2014

The Antiklinalbugt Formation of northeast Greenland comprises peritidal to subtidal carbonate sediments, deposited in shallow shelf settings during an early Tremadocian transgressive-regressive megacycle. The succession of shales and microbial, muddy and grainy limestone, with minor dolostone at the base and top, terminates at the cryptic Fimbulfjeld disconformity. The formation has yielded trilobites collected on Ella Ø, Albert Heim Bjerge, and Kap Weber by C. Poulsen (1920s and 1930s), J. W. Cowie and P. J. Adams (1950s), and during recent field studies in 2000 and 2001. The fauna includes dimeropygidsTulepyge cowieiandT. tesellan. spp., hystricuridsMillardicurusandHystricurus, and several species ofSymphysurina. Micragnostus chiushuensis(Kobayashi, 1931) is rare, as areChasbellussp.,Clelandiasp., andLunacrania?. The presence of severalSymphysurinaspecies places the Antiklinalbugt Formation within theSymphysurinaZone.Chasbellusindicates the upper (lower Ordovician) part of theSymphysurinaZone for the lower upper Antiklinalbugt Formation. Conodonts place the middle lower formation in theCordylodus intermediusconodont Biozone, the lower upper part in theCordylodus angulatusconodont Biozone and the uppermost part in theRossodus manitouensisconodont Biozone. This combined fauna is characteristic of the upper Skullrockian Stage of the Ibexian Series, with the lower part of the Antiklinalbugt Formation lying within the uppermost Cambrian of North America, and the upper part within the lower Ordovician. The entire formation lies within the global Tremadocian Stage of the early Ordovician.
Sinaithyris, a New Name for the Middle Jurassic Terebratulid Brachiopod Cooperithyris Feldman, Radulović, Hegab, and Radulović, 2012 Preoccupied by Cooperithyris Tchorszevsky, 1988
Authors: Feldman Howard R. , Radulović Vladan J. , Hegab Adel A. A. , Radulović Barbara V.
Published: October 2014

Feldman, Radulović, Hegab, and Radulović (2012) established the genus Cooperithyris for an upper Bathonian terebratulid brachiopod from Gebel Engabashi, northern Sinai, based on the type species C. circularis Feldman, Radulović, Hegab, and Radulović, 2012. Recently, Professor Fernando Alvarez, (Departamento de Geologia, Universidad de Oviedo, Oviedo, Spain) informed us of the existence of the homonym Cooperithyris Tchorszevsky, 1988, from the Pliensbachian–Toarcian of the Transcaucasus. In accordance with the International Code of Zoological Nomenclature (ICZN 1999, articles 53 and 60), we herein propose the replacement name, Sinaithyris, for the junior homonym. The new name is in reference to the Sinai Peninsula on which Gebel Engabashi is located and from which the specimens were collected.
In-Isolation Cyclic Load-Extension Behavior of Two Geogrids
Authors: Bathurst R.J. , Cai Z.
Published: October 2014

The paper describes a series of in-isolation cyclic load-extension tests performed on HDPE,and PET geogrid specimens. The specimens were tested at five different loading frequencies: 0.1, 0.5, 1.0, 2.0 and 3.5 Hz, and over a range of load amplitudes. The load-strain behavior of the geogrid materials is characterized using two distinct features of the cyclic response: 1) non-linear hysteresis unload-reload loops; and 2) a load-strain cap that contains all hysteresis curves. The cyclic load-strain response of the HDPE and PET geogrid specimens is demonstrated to be significantly different from the static response of the same materials tested according to the current ASTM D 4595 method of test. The load-strain caps for HDPE geogrid specimens are found to be very sensitive to the loading frequency and loading history while those of the PET geogrid appear to be relatively insensitive. The hysteresis load-strain behavior of both types of geogrids depends strongly on the load level and loading frequency.
HDPE Geosynthetics: Premature Failures and Their Prediction
Authors: Peggs I.D. , Kanninen M.F.
Published: October 2014

Most manufactured products and engineering works perform satisfactorily. Those that do not, fail at an unexpected defect not because of a gross miscalculation of basic service life. It is necessary to identify such unexpected failure-initiating defects and to understand at what size such defects become critical and at what rate induced cracks will propagate. HDPE is an engineering thermoplastic that has been used in geotechnical and civil engineering applications for many years as natural gas distribution pipes, waste containment geomembranes, and soil reinforcement. The predominant mode of premature failure of HDPE pipe and geomembrane is a quasi-brittle fracture initiated at stress concentrating surface notch geometries and/or unexpected point stresses. Such failures occur due to the fundamental stress cracking susceptibility of HDPE. The semi-crystalline, microstructure of HDPE, which is responsible for its excellent chemical resistance and strength properties, is also responsible for its susceptibility to stress cracking. The characteristics of stress cracking in pipe and geomembrane are reviewed and extended to geogrids. An overview of the test methods used to assess the mechanical durability of HDPE is presented together with methods used to relate accelerated test results to service lifetimes. Such methods may also be appropriate for geogrids.
A Numerical Model for Analyzing Long-Term Performance of Geosynthetic-Reinforced Soil Structures
Authors: Helwany M.B. , Wu J.T.H.
Published: October 2014

A numerical model is developed to investigate long-term soil-geosynthetic interaction in typical geosynthetic-reinforced soil structures. The numerical model employs the finite element method with a time marching scheme while incorporating a generalized creep law for geosynthetics and a visco-plastic constitutive law for soil. To verify the numerical model, two well-controlled laboratory long-term soil-geosynthetic performance tests were analyzed. One performance test used cohesive backfill and the other a granular backfill. As a result of soil-geosynthetic interaction, the cohesive backfill test exhibited significant deformation with time, while the granular backfill test demonstrated little deformation with time. It is shown that the numerical model is capable of simulating the long-term soil-geosynthetic interactive behavior of both long-term performance tests. To illustrate the importance of the long-term soil-geosynthetic interaction, the numerical model was used to analyze the long-term performance of two 3 m high geosynthetic-reinforced soil retaining walls, one with a cohesive backfill and the other with a granular backfill.
Relationships Between Uniaxial and Biaxial Stresses and Strains in Geosynthetics
Authors: Soderman K.L. , Giroud J.P.
Published: October 2014

Theoretical relationships between tensile characteristics (i.e. modulus, yield stress and yield strain) of geosynthetics in uniaxial and biaxial states of stress are proposed. The use of the relationships is illustrated through practical applications which show that the tensile characteristics of geosynthetics vary greatly depending on the stress state.
Relaxation Behavior of Thermally-Induced Stress in HDPE Geomembranes
Authors: Lord A.E. , Soong T.Y. , Koerner R.M.
Published: October 2014

A series of stress relaxation laboratory experiments have been performed on high density polyethylene (HDPE) geomembranes, where the stress was induced by temperature changes. It was found that for practical rates of temperature decrease, the tensile stresses were for the most part relaxed as they were applied. Therefore, very little stress relaxation occurred (even for times up to one week) after the final lower temperature was achieved. This experimental finding has some practical implications for the installation of geomembranes in the field.
Subgrade Stabilisation with Geotextiles
Authors: Lawson C.R.
Published: October 2014

Subgrade stabilisation is the largest single application for geotextiles by volume. As environmental and population pressures become more severe, infrastructure projects will be directed further towards locations where ground conditions are marginal. This trend, in addition to the cost-benefit of geotextiles, is likely to result in increased usage of geotextiles. There are two fundamental aspects of design when geotextiles are used for subgrade stabilisation: the required thickness and quality of pavement materials to be placed above the geotextile; and the required properties of the geotextile. The thickness and quality of pavement materials is dependent upon the level of serviceability required of the completed pavement structure. The required geotextile properties are dependent upon the strength of the subgrade, the particle size of the granular layer above the geotextile, and groundwater conditions. Currently, selection of the appropriate geotextile properties for subgrade stabilisation is most commonly performed by a combination of empirical classification and design. The various procedures adopted in the selection of appropriate geotextile properties are highlighted in this paper.
Unified Design Approach to Geosynthetic Reinforced Slopes and Segmental Walls
Authors: Leshchinsky D. , Ling H. , Hanks G.
Published: October 2014

Geosynthetic reinforced slopes and walls are being increasingly constructed to perform as permanent structures. Facing blocks are used to improve the aesthetic appearance of walls and to simplify their construction. This paper presents a unified design approach, based on limit equilibrium analysis, that considers the various aspects of stability of reinforced soil structures including the stabilizing effects of facing blocks. Possible instabilities due to tied-back failure, compound failure, direct sliding, and overturning are considered. The design procedure is validated using the test results of two full-scale walls. The results of parametric studies indicate that facing interblock friction significantly reduces the required geosynthetic length and strength for a near-vertical wall. This effect diminishes as the slope angle reduces. Even though the soil-block friction reduces the required geosynthetic strength, it increases the required length of geosynthetic. Examples, and general guidelines for appropriate selection of design material properties and safety factors, are discussed
Theoretical Analysis of Geomembrane Puncture
Authors: Giroud J.P. , Badu-Tweneboah K. , Soderman K.L.
Published: October 2014

A theoretical analysis of the mechanism of geomembrane puncture based on a simple model is presented. The analysis shows that the geomembrane puncture resistance depends on the diameter of the contact area between the geomembrane and the puncturing object, the thickness of the geomembrane, and the tensile characteristics of the geomembrane. An equation is established that makes it possible to express the geomembrane puncture resistance measured in a probe test as a function of the geomembrane characteristics and the diameter of the probe. Predictions made with this equation are found to be consistent with the limited laboratory test data which were reviewed. The analysis is then used to establish a relationship between a geomembrane resistance to puncture measured in a laboratory probe test and the resistance to puncture of a geomembrane subjected to pressure applied by a liquid while resting on a layer of stones of approximately uniform size and shape. A special relationship is presented for the case of rounded stones. The paper also presents relationships between geomembrane resistances to puncture by stones under different sets of conditions characterized by the stone size and shape, and the geomembrane thickness and tensile characteristics. The use of these relationships is illustrated by design examples.
Soil Reinforcement Practice for Fills Over Soft Ground in Japan
Authors: Ochiai H. , Watari Y. , Tsukamoto Y.
Published: October 2014

This paper summarizes the theory and practice of geosynthetic reinforcement of fills over extremely soft ground in Japan. Emphasis is placed on artificially reclaimed soft ground composed of marine soils which are characterized by high water contents and low shear strengths. The use of geosynthetics facilitates the movement of construction equipment and the placement of fill. The bearing capacity of the ground is improved by using high strength geosynthetics. Classical bearing capacity theory, cable theory combined with modulus of subgrade reaction theory, and plate theory are found to be useful in designing embankments on soft ground. The empirical parameters used in these theories are available for most projects. The unique geotechnical conditions of the soft ground typically inhibit the construction procedures specified in the design. The experience gained from past geosynthetic reinforced fill projects, one of which is highlighted in the paper, facilitates the improvement of fill placement and spreading techniques on soft ground.
Geotextile Characterization and Pore-Size Distribution: Part I. A Review of Manufacturing Processes
Authors: Bhatia S.K. , Smith J.L.
Published: October 2014

The rapidly growing geotextile industry has led to a variety of new geotextile manufacturing processes and products. Many of these geotextiles have similar physical properties (mass per unit area and thickness) but have completely different pore-size distributions. The two main types of geotextiles, woven and nonwoven, have very different pore structures. In addition, the pore openings of both woven and nonwoven geotextiles are dependent on the fiber type and the manufacturing process. Designers must be aware of the differences in pore structure of various types of geotextiles in order to properly select a geotextile for filtration applications. Manufacturers must also be aware that changes in the manufacturing process of a geotextile will alter the pore-size distribution of the geotextile.
Application of Geotextile/Geomembrane Composite Liner for Infiltration Prevention in Xiaolingtou Rock-Fill Dam
Authors: Tao T. , Yan J. , Tao X. , Fu F. , Zhou H.
Published: October 2014

The rock-fill dam at the Xiaolingtou Reservoir is 36.4 m high and uses a geotextile/geomembrane composite liner to prevent seepage. The composite consists of geotextiles bonded to both sides of a geomembrane. The seepage prevention properties of the composite are theoretically analysed, and equations to calculate the design strength and geomembrane thickness have been introduced. The transition material on the side slopes of the dam directly effects the selection of a design strength for the composite. The laboratory testing program carried out to optimize the cushion material gradation of for the Xiaolingtou rock-fill dam is described. The horizontal displacement, vertical settlement, maximum and minimum principal stresses in the rock-fill dam during construction and water storage periods have been analysed by the finite element method.
Geotextile Characterization and Pore-Size Distribution: Part III. Comparison of Methods and Application to Design
Authors: Bhatia S.K. , Smith J.L. , Christopher B.R.
Published: October 2014

Geotextiles are widely used in filtration applications. For continued growth in this area, it is critical that geotextiles be properly designed for these applications to prevent failures. The geotextile property that is most directly related to the design of a geotextile as a filter is the pore-size distribution of the geotextile. The main objective of this study was to compare the performance of the following six different test methods to evaluate the pore-size distribution of geotextiles: dry sieving, hydrodynamic sieving, wet sieving, bubble point method, mercury intrusion porosimetry, and image analysis. Twenty-eight geotextiles from five different manufacturers were evaluated. In this paper, the pore-size distribution results obtained from these methods are compared. The differences in pore opening results by different methods are illustrated using a design example.
Shear Behavior of Reinforced Geosynthetic Clay Liners
Authors: Stark T.D. , Eid H.T.
Published: October 2014

Ring shear tests were performed to evaluate the effect of bentonite on the interface shear strength between a geomembrane and a reinforced geosynthetic clay liner (GCL), and the internal shear behavior of reinforced GCLs. The tests yielded an interface shear strength that is in agreement with the back-calculated shear strength values from two test pads that deformed at the U.S. Environmental Protection Agency GCL Test Section in Cincinnati, Ohio, USA. The ring shear tests showed that the internal shear strength of reinforced GCLs depends on the following two factors: (i) resistance against reinforcing fiber pull-out and/or tearing; and, (ii) shear strength of bentonite. The laboratory tests indicate that fiber resistance is the predominant internal shear strength factor. Recommendations are presented for the rate of shear that should be used for internal shear testing of reinforced GCLs.
Polymer Geogrids for Bridging Mining Voids
Authors: Bridle R.J. , Jenner C.G.
Published: October 2014

Full-scale field tests to determine the support provided by polymer geogrids in typical road construction over old coal mining areas were carried out under controlled conditions. The results are evaluated with the purpose of proposing a design approach for the materials used in the trial tests. A number of analytical methods are defined and combined to develop an appropriate design approach that matches the measured field results as closely as possible.
Modelling Geosynthetic-Reinforced Granular Fills Over Soft Soil
Authors: Yin J.H.
Published: October 2014

In this paper, a new one-dimensional mathematical model is proposed for modelling geosynthetic-reinforced granular fills over soft soils subject to a vertical surcharge load. The geosynthetic reinforcement consists of a membrane (geogrid, or geotextile) placed horizontally in engineered granular fill, which is constructed over soft soil. The proposed model is mainly based on the assumption of a Pasternak shear layer. A new approach that consists of incorporating a deformation compatibility condition into the model is introduced. The compatibility condition eliminates the need for two uncertain model parameters that are required to calculate the shear stresses between the top and bottom granular fill layers and the geosynthetic layer. This compatibility condition also makes it possible to include the geosynthetic stiffness in the model. The results from the proposed model are compared to results from a two-dimensional finite element model and three other one-dimensional models reported in the literature. The comparison reveals that the proposed model gives similar results with respect to the settlement of a geosynthetic-reinforced granular base on soft soft and the mobilised tension in the geosynthetic layer.
Uplift of Geomembranes by Wind - Extension of Equations
Authors: Zornberg J.G. , Giroud J.P.
Published: October 2014

This technical note presents an extension of earlier analytical methods published in 1995 by Giroud et al. for evaluating the uplift of geomembranes by wind. The extension incorporates: (i) the influence on wind uplift of the slope inclination of an exposed geomembrane; and (ii) a more accurate expression of the tension-strain relationship in a wind uplifted geomembrane. Use of the revised methods is particularly relevant for projects in which the exposed geomembrane mass per unit area is high, the slope inclination of the exposed geomembrane is steep, and the exposed geomembrane is subjected to strains due to mechanisms other than the wind (e.g. gravity, temperature) prior to wind uplift. Also, the revised equations are particularly appropriate for dimensioning a protective layer placed on top of the geomembrane to prevent wind uplift. The information provided in this technical note may be of particular significance for projects in which an exposed geomembrane is contemplated as the final cover for waste containment systems with steep slope configurations.
Load Transfer Mechanism in Pull-Out Tests
Authors: Alobaidi I.A. , Hoare D.J. , Ghataora G.S.
Published: October 2014

This paper presents a numerical method to predict soil-geotextile interface friction parameters. A strain softening model was used to simulate the relationship between shear stress and horizontal displacement at the soil-geotextile interface. Pull-out tests were performed on two types of geotextile, with different tensile stiffnesses, embedded in a granular soil. For each geotextile, pull-out tests were performed at confining pressures of 20, 50, 100, and 200 kPa. It was found that, unless breakage of the geotextile occurs, the peak pull-out force occurs after a small displacement of the free end of the geotextile. At the peak pull-out force, the maximum shear stress occurs near the free end of the geotextile while the shear stress at the loaded end is at or near a residual value. The use of an average interface friction angle overestimates pull-out resistance. The numerical technique developed in this paper provides more accurate values for soil-geotextile interface friction parameters.
Effect of Wall Facing on the Seismic Stability of Geosynthetic-Reinforced Retaining Walls
Authors: Ismeik M. , Guler E.
Published: October 2014

This study examines the results of a seismic stability analysis of geosynthetic-reinforced retaining walls subjected to different seismic loading conditions. The effect of wall facing thickness on stability is investigated for a full-height concrete facing by using the two-wedge failure mechanism. An analytical method is developed to correlate the effect of facing thickness with the amount of geosynthetic reinforcement required, using the limit equilibrium analysis in relation to the seismic forces. The results are presented in chart form.
Simplified Seismic Design Procedure for Geosynthetic-Lined, Solid-Waste Landfills
Authors: Bray J.D. , Rathje E.M. , Augello A.J. , Merry S.M.
Published: October 2014

This paper critically reviews seismic design practices in light of the observed performance of landfills during recent earthquakes. Developments in these areas are summarized as follows: earthquake ground motions, dynamic waste fill properties, dynamic responses of geomembranes and their interfaces, nonlinear dynamic response analysis, and seismic stability evaluation. A newly developed simplified seismic analysis procedure that requires the most critical factors be addressed during a seismic performance evaluation is presented. The underlying seismic analysis procedure has been validated against observed performance of landfills shaken by the 1989 Loma Prieta and 1994 Northridge, California earthquakes. The procedure is comprehensive in that it requires: (i) characterization of the design bedrock motions in terms of intensity, frequency content, and duration; (ii) estimation of the seismic loading at the base and cover of the landfill; (iii) e valuation of performance in terms of seismically induced permanent deformations; and (iv) appropriate engineering judgment.
A Study of Biodegradable Geotextiles Used for Erosion Control
Authors: Ogbobe O. , Essien K.S. , Adebayo A.
Published: October 2014

The physical properties of two geotextiles made of natural fibres, malvaceae and penduculata, are presented. The effectiveness of these biodegradable geotextiles in preventing soil erosion was studied and compared with a polypropylene fibre geosynthetic erosion control mat. A rainfall simulation apparatus was used on protected and unprotected slopes that were inclined at 10, 15, 20, 30, and 45° to the horizontal. The effective cover factor, defined as the ratio of soil loss from a protected slope to the soil loss from an unprotected slope, ranged from 0.24 to 0.49 for the penduculata geotextile and from 0.47 to 0.73 for the malvaceae geotextile. The effective cover factor ranged from 0.16 to 0.27 for the polypropylene erosion control mat.
Filtration Performance Testing of Geotextiles for Vacuum Consolidation Drains
Authors: Haegeman W. , Impe W.F. Van
Published: October 2014

The effectiveness of a drainage system used for vacuum consolidation of dredged sludge is very important since it affects consolidation of the sludge and the removal of drained water. The performance of soil-geotextile systems in a filtration test under unidirectional flow is reported for five drains. A new apparatus was developed for filtration tests under a simulated vacuum pressure and tests were conducted with sludge and different nonwoven geotextiles in order to evaluate the clogging potential and retention capacity of these materials under rather severe combinations of geotextile and soil characteristics. Testing under hydraulic gradients of 40 to 60, and for a duration of 200 hours, yielded a steady state permeability value for four sludge-geotextile systems. Progressive increase of the permeability was observed for one geotextile. Results from the filtration tests are compared and discussed.
Laboratory Survivability of Nonwoven Geotextiles on Open-Graded Crushed Aggregate
Authors: Elvidge C.B. , Raymond G.P.
Published: October 2014

A laboratory method of assessing survivability of a nonwoven geotextile laid on open-graded crushed aggregate was developed. Preliminary suggestions for the application to compaction forces and/or traffic forces are given. Phase 1 involved compaction using a modified California Bearing Ratio (CBR) test with a geotextile sandwiched between two soil layers. Phase 2 involved tension testing of the damaged geotextile. In order to undertake Phase 2, a 200 mm wide-width strip tensile test methodology that did not use grips was developed and is presented. The test variables examined in the CBR phase of the testing were the particle size of the cover material, the mass of the geotextile, and the compaction energy of the CBR tests (via the ram mass and drop height). The particle size of the bedding material and the thickness of both the cover and bedding material were kept constant. The results, in terms of damage to the geotextile, show: (i) the smaller the compaction energy the less geotextile damage; (ii) the greater the mass per unit area, or thickness, of the geotextile the less geotextile damage; and (iii) the smaller the particle size of the aggregate overlying the geotextile the less geotextile damage. This last result was very evident when the particle size was < 2 mm. The tensile testing technique used a geotextile loop joined with a rapidly applied hot glue that permitted immediate testing. The loop technique also avoided the lateral restraining effect of full-width grips.
Soil-Geosynthetic Interaction - Influence of Soil Particle Size and Geosynthetic Structure
Authors: Lopes M.J. , Lopes M.L.
Published: October 2014

This paper reports the results of pullout tests on five different geosynthetics embedded in two different granular soils. Soil and geosynthetic properties are described and soil-geosynthetic interaction behaviour is studied. Based on the results of pullout tests, the influence of soil particle size, geosynthetic structure, and the role of geogrid bearing members are discussed. The main conclusion is that the influence of soil particle size on soil-geosynthetic interaction is important, but its significance depends on several factors. With geogrids, the relative sizes of soil particles and geogrid apertures, and the thickness of the geogrid bearing members, determine soil-geogrid interface shear resistance. A marked increase in soil-geogrid interface shear resistance was observed when the soil contained a significant percentage of particles with sizes slightly greater than the thickness of the geogrid bearing members, but smaller than the geogrid apertures. Tests, on geogrids in which the bearing members had been cut, show a significant decrease in soil-geogrid interface shear resistance. The influence of soil particle size is less important for geotextiles and geocomposites. Although the structure of geotextiles and geocomposites has an effect on soil-reinforcement interface behaviour, mobilised pullout resistance is also affected by the axial tensile stiffness of geotextiles and geocomposites.
Engineering Behaviour of Fibre-Reinforced Pond Ash and Silty Sand
Authors: Kumar R. , Kanaujia V.K. , Chandra D.
Published: October 2014

This note presents the results of laboratory investigations conducted on silty sand and pond ash specimens reinforced with randomly distributed polyester fibres. The test results reveal that the inclusion of fibres in soils increases the peak compressive strength, CBR value, peak friction angle, and ductility of the specimens. It is concluded that the optimum fibre content for both silty sand and pond ash is approximately 0.3 to 0.4% of the dry unit weight.
Discharge Capacity of Prefabricated Vertical Drains Confined in Clay
Authors: Miura N. , Chai J.C.
Published: October 2014

This paper reports the long-term discharge capacities of four types of prefabricated vertical drains (PVDs) confined in clay. The results indicate that under clay confinement, the PVD discharge capacities significantly reduced with time. The discharge capacity reduction may be caused by creep deformation of the PVD filter or clogging of the drainage channels. PVD filter creep test results indicated that, for the conditions considered, creep deformation was limited, which implies that clogging is the main cause of the discharge capacity reduction. Hydraulic shocks were applied, which partially unclogged the PVD, recovering a significant amount of the discharge capacity. The higher the PVD hydraulic gradient and the larger the shape factor of the drainage channel (defined as the drainage area per channel divided by its perimeter length), the less discharge capacity reduction with time. However, there was no clear trend regarding the effect of the apparent opening size, O 95, of the filter on long-term discharge capacity. Based on the test results, an empirical equation was proposed for estimating the long-term clay-confined discharge capacity by using short-term rubber membrane-confined test results. Regarding long-term discharge capacity, it is recommended that a PVD with a larger drainage area per channel (approximately 3 mm2) and a larger drainage channel shape factor (larger than 0.4 mm) should be selected.
Finite Element Study of a Geosynthetic-Reinforced Soil Retaining Wall With Concrete-Block Facing
Authors: Ling H.I. , Cardany C.P. , Sun L-X. , Hashimoto H.
Published: October 2014

This paper focuses on the results of finite element modeling of a full-scale, concrete-block, geosynthetic-reinforced soil retaining wall constructed at the Public Works Research Institute in Japan. A nonlinear hyperbolic geosynthetic model was incorporated into a computer program that is capable of simulating soil-structure interaction behavior. The soil was simulated using a hyperbolic model while the block-block and soil-block interactions were simulated using interface elements. Comparison of numerical and measured experimental results indicated that the finite element model is capable of simulating the construction behavior of concrete-block geosynthetic-reinforced soil structures.
The Influence of Partial Clogging and Pressure on the Behaviour of Geotextiles in Drainage Systems
Authors: Palmeira E.M. , Gardoni M.G.
Published: October 2014

Nonwoven geotextiles have been used for drainage and filtration in geotechnical engineering works for many years. Concerns related to drainage capacity and clogging potential still remain as factors that restrain a broader use of geotextiles for drainage systems, particularly in major engineering projects. This paper presents the test results of the hydraulic characteristics of partially clogged geotextiles under pressure. Partial clogging can occur during spreading and compaction of soil on geotextiles or throughout the service life of the drainage system. Geotextile specimens, artificially clogged in the laboratory and exhumed from actual field works, were tested to assess their normal and longitudinal permeabilities under different levels of soil impregnation and normal stresses. The results obtained showed that partial clogging significantly influenced the mechanical and hydraulic characteristics of nonwoven geotextiles and that soil impregnation was not necessarily detrimental to the geotextile longitudinal permeability under stress. Comparisons of test and predicted results, confirmed that the expression reported by Giroud in 1996 is a useful tool for the prediction of nonwoven geotextile permeabilities under virgin and soil impregnated conditions. Data on the impregnation levels of geotextile specimens exhumed from actual field works are also presented and discussed.
Comparison of the Durability of Geotextiles in an Alkaline Mine Tailings Environment
Authors: Grubb D.G. , Diesing W.E. , Cheng S.C.J. , Sabanas R.M.
Published: October 2014

This is the last of a three-part study (Grubb et al. 1999, 2000) that explores the issues related to the use and durability of geotextiles in Andean mining environments. Additional outdoor exposure tests were completed on a woven multi-filament polyester (PET) geotextile, and on two nonwoven needle-punched polypropylene (PP) geotextiles with carbon black in Vijus, Peru, and Atlanta, Georgia, USA. The average retained strengths of each geotextile in both locations did not exceed 60%. Five geotextile samples (those previously mentioned and two additional nonwoven needle-punched PET geotextiles) were also embedded in freshly deposited alkaline tailings with a pH of 11.3 and 178 mg/L total cyanide. The retained strengths of the lighter PET geotextile varied from approximately 43 to 338%. The average retained strengths of the four nonwoven geotextiles ranged from approximately 84 to 92%. Two geotextiles placed directly on the surface of the tailings demonstrated that chemical-induced erosion processes could be mitigated. Batch immersion experiments were performed on the PET geotextiles in two alkaline sodium hydroxide solutions (one containing cyanide) to quantify whether the cyanide ion produced any degradation in addition to that measured for the hydroxyl ion at the same pH. The retained strength data indicated that the alkaline solution containing cyanide best matched the alkaline mine tailings environment.
Measurement of Geotextile-Water Characteristic Curves Using a Controlled Outflow Capillary Pressure Cell
Authors: Knight M.A. , Kotha S.M.
Published: October 2014

The present paper describes the use of a controlled outflow capillary pressure cell for the measurement of geotextile-water characteristic curves. Fine sand with a known soil-water characteristic curve and a geotextile column drainage experiment were used to validate the controlled outflow cell. The controlled outflow cell was also used to measure drainage geotextile-water characteristic curves for one, three, and six vertically stacked nonwoven geotextile specimen layers. Test results indicate the following: (i) the controlled outflow cell can measure a complete nonwoven drainage geotextile-water characteristic curve with a water entry pressure of 50 mm; (ii) vertical stacking of the nonwoven geotextile has little influence on the geotextile-water characteristic curve; and (iii) a geotextile-water characteristic curve can be measured in less time when compared with Klute’s method. Test results also indicate that ASTM D 854 may be used to determine the specific gravity of the nonwoven geotextile.
Experimental Investigation of the Interaction Mechanism at the EPS Geofoam-Sand Interface by Direct Shear Testing
Authors: Xenaki V.C. , Athanasopoulos G.A.
Published: October 2014

The results of laboratory direct shear tests conducted at the expanded polystyrene (EPS) geofoam-sand interface are presented in this paper. The sands used in the tests were composed of rounded to subangular particles with values of mean particle size ranging from 0.28 to 2.17 mm and void ratios ranging from 0.51 to 0.72. The EPS geofoam was of two different densities: 10 and 20 kg/m3. The test results are expressed in the form of shear stress versus normal stress in direct shear failure envelopes, which were found to be nonlinear. The curved interface failure envelopes were approximated by piecewise linear envelopes composed of three linear segments corresponding to three types of phenomenological interaction mechanism, which develop successively for increasing values of normal interface stress: purely frictional, frictional-adhesional, and purely adhesional. A simple conceptual framework is proposed that qualitatively explains the observed interface behavior in terms of the normal interface stress, EPS geofoam hardness (or density), interface relative roughness (which incorporates the mean particle size), shape of sand particles, and void ratio of sand. The experimental results are compared to similar results reported in the literature for HDPE geomembrane-sand interfaces. Apparent values of interface friction angle, δ, and adhesion, ca, are proposed in the paper for the tested sands and for specific ranges of normal interface stresses and the two EPS geofoam densities.
FEM Simulation of the Bearing Capacity of Level Reinforced Sand Ground Subjected to Footing Load
Authors: Kotake N. , Tatsuoka F. , Tanaka T. , Siddiquee M.S.A. , Huang C.-C.
Published: October 2014

To obtain a better understanding of the bearing capacity characteristics of reinforced sand subjected to a footing load and the associated reinforcing mechanisms, results from plane strain laboratory model tests were simulated using a nonlinear elasto-plastic finite element model (FEM). The following factors, which affect the strength and deformation of sand, were considered in the simulations: (i) confining pressure; (ii) anisotropy; (iii) nonlinear strain-hardening and strain-softening; (iv) dilatancy; and (v) strain localization into a shear band(s) having a width proportional to the particle size. Simulated load-settlement relationships were generally in good agreement with the physical experimental results. The strain and stress fields obtained from the FEM analysis clearly reveal that the ground failure is extremely progressive. The peak strength is never mobilized simultaneously along the potential failure planes.
Microscale Study of Geomembrane-Geotextile Interactions
Authors: Frost J.D. , Lee S.W.
Published: October 2014

This paper summarizes the results of a study that used quantitative measures of surface roughness as the basis for investigating the role of topography on the interface shear mechanism of geomembrane-geotextile interfaces. The results show that the interface strength and mechanisms can be quantitatively related to the surface roughness of the geomembrane. The peak and residual interface strengths increase dramatically through the use of textured geomembranes. For textured geomembranes, the peak interface strength is due to the micro-texture of the geomembrane, however, the residual interface strength is primarily attributed to macro-scale surface roughness that pulls and breaks the filaments of the geotextile. The effect of geomembrane wear on the stress-strain response is quantified. The findings of this study provide a quantitative framework that can lead to a significantly improved basis for the selection of geotextiles and geomembranes in direct contact.