The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform

Gerald P Raymond - One of the best experts on this subject based on the ideXlab platform.

  • Railway rehabilitation Geotextiles
    Geotextiles and Geomembranes, 1999
    Co-Authors: Gerald P Raymond
    Abstract:

    Abstract Geotextiles were introduced into North American railway tracks in the 1970s based on non-railway proven applications so as to correct some of the major track support problems. Failures soon resulted. These failures were studied by examining both the track conditions and the change in the properties of the exhumed Geotextiles at different time intervals. Soil fouling content, change in permeability ratio, change in geotextile strength and the like geotextile properties were examined. The study established a railway rehabilitation geotextile's primary functions/properties as separation, drainage, filtration, abrasion resistance and elongation. From the study a track rehabilitation geotextile and installation specification was established for use in North American tracks. After several years Geotextiles manufactured and installed in accordance with the recommendations were exhumed. The performance of these installations were found to be satisfactory and have continued to be installed since early 1981 on Canadian National Railway's Maritime Region and other railway companies tracks. In conclusion, it is evident that correctly installed Geotextiles meeting the final specification are able to give satisfactory performance in track rehabilitation applications and are able to be cost effective.

  • Durability of Geotextiles in railway rehabilitation
    Transportation Research Record, 1994
    Co-Authors: Gerald P Raymond
    Abstract:

    The durability of Geotextiles installed in railway rehabilitation applications is investigated by examining the track conditions and the change in properties of exhumed Geotextiles at different time intervals. Properties examined include soil fouling content, change in permeability ratio, and change in geotextile strength. These properties are related, as appropriate, to characteristics such as filtration opening size. The results are discussed in terms of the geotextile's primary functions of filtration, drainage, separation, abrasion resistance, and elongation. Data collected before 1982 were used to develop a track rehabilitation geotextile specification for use without a capping sand. Data collected after 1982 were used to support and confirm the validity of the specification. This specification was adopted and has been in use in the Canadian National Railways Maritime Region since 1981. It has also been used for rehabilitation of other railway company tracks. Correctly installed Geotextiles meeting the specification have given satisfactory performance and have been cost-effective.

Amit Rawal - One of the best experts on this subject based on the ideXlab platform.

  • interface shear characteristics of jute polypropylene hybrid nonwoven Geotextiles and sand using large size direct shear test
    Geotextiles and Geomembranes, 2014
    Co-Authors: M M A Sayeed, Janaki B Ramaiah, Amit Rawal
    Abstract:

    Abstract In this study, large-size direct shear tests were conducted to determine the interfacial shear characteristics of sand–geotextile under three different normal stresses. The Geotextiles used in the present study were hybrid needlepunched nonwovens containing defined weight proportions of jute and polypropylene fibers. Subsequently, the interfacial shear characteristics of hybrid and that of a nonwoven geotextile consisting of solely polypropylene fibers with sand were compared and analyzed under different normal stresses. Initial higher shear stiffness of sand-polypropylene Geotextiles was observed corresponding to sand-hybrid Geotextiles specifically under higher normal stresses. Nevertheless, the contact efficiency of sand-hybrid nonwovens was similar to that of sand-polypropylene Geotextiles. The surface morphology of sand particles has been investigated based on the images obtained from scanning electron microscopy (SEM) and quantitatively analyzed by means of Wadell roundness and degree of angularity methods.

  • Pore size distribution of hybrid nonwoven Geotextiles
    Geotextiles and Geomembranes, 2011
    Co-Authors: Amit Rawal, Harshvardhan Saraswat
    Abstract:

    Abstract Pore size distribution has become a prerequisite in determining the performance of Geotextiles for various functions including filtration, separation and reinforcement. The pore structure and morphology in a nonwoven geotextile are known to be complex and it becomes further complicated in hybrid nonwoven Geotextiles consisting of two types of fibers. In this study, a modified model of pore size distribution of hybrid nonwoven Geotextiles has been proposed based on sieving-percolation pore network theory. A comparison has been made between theoretical and experimental pore size distributions of hybrid needlepunched nonwoven Geotextiles consisting of predefined weight proportions of viscose and polyester fibers. The weight proportions of the constituent fibers have been theoretically analysed for obtaining the desired pore size distributions of hybrid nonwoven Geotextiles.

  • Geotextiles production properties and performance
    Textile Progress, 2010
    Co-Authors: Amit Rawal, Tahir Shah, Subhash Anand
    Abstract:

    The monograph critically reviews most commonly used geotextile structures, their properties and performance characteristics. In general, both natural and synthetic fibres are used for the production of Geotextiles, and the advantages and disadvantages of each type of fibre are discussed for various applications of Geotextiles. The important functions of Geotextiles, i.e. filtration, drainage, separation and reinforcement have been identified and have been related to several properties and major applications of Geotextiles. Various geotextile properties, namely mechanical, hydraulic and chemical and their test methods have been critically discussed. A process–structure–property relationship for most commonly used Geotextiles is also analysed. Furthermore, the design of a geotextile is of paramount importance for any civil engineering application. Thus, the design criteria for various functions of Geotextiles have been addressed. Subsequently, the durability characteristics of geotextile have been introduce...

N Sanka - One of the best experts on this subject based on the ideXlab platform.

  • laboratory performance of unpaved roads reinforced with woven coir Geotextiles
    Geotextiles and Geomembranes, 2009
    Co-Authors: E A Subaida, S Chandrakara, N Sanka
    Abstract:

    Abstract The results of an experimental study conducted to investigate the beneficial use of woven coir Geotextiles as reinforcing material in a two-layer pavement section, are presented. Monotonic and repeated loads were applied on reinforced and unreinforced laboratory pavement sections through a rigid circular plate. The effects of placement position and stiffness of geotextile on the performance of reinforced sections were investigated using two base course thicknesses and two types of woven coir Geotextiles. The test results indicate that the inclusion of coir Geotextiles enhanced the bearing capacity of thin sections. Placement of geotextile at the interface of the subgrade and base course increased the load carrying capacity significantly at large deformations. Considerable improvement in bearing capacity was observed when coir geotextile was placed within the base course at all levels of deformations. The plastic surface deformation under repeated loading was greatly reduced by the inclusion of coir Geotextiles within the base course irrespective of base course thickness. The optimum placement position of coir geotextile was found to be within the base course at a depth of one-third of the plate diameter below the surface.

  • experimental investigations on tensile and pullout behaviour of woven coir Geotextiles
    Geotextiles and Geomembranes, 2008
    Co-Authors: E A Subaida, S Chandrakara, N Sanka
    Abstract:

    Abstract Results of an experimental programme to investigate the tensile and interface properties of woven coir Geotextiles are presented. Tension tests were conducted on coir fibres, yarns and woven Geotextiles at different gauge lengths and strain rates. Based on statistical analysis, a gauge length of 150 mm and a strain rate of 5%/min was adopted for the purpose of characterization of tensile properties. Tensile strength of woven coir geotextile was expressed as a function of fibre strength, yarn properties and weaving pattern. Pullout test and modified direct shear test were conducted on Geotextiles in granular soils of different grain sizes. At low normal stress, bond resistance of coir geotextile–sand interface obtained was more than shear strength of soil. But consistent values of bond resistance were not obtained at higher normal stresses. The opening size of mesh relative to the soil grain size influenced the pullout interaction between soil and geotextile. For closely woven Geotextiles, the pullout resistance did not vary much in soils of different grain sizes, whereas for Geotextiles with open meshes, pullout resistance obtained was more in fine sand compared to coarse sand.

E A Subaida - One of the best experts on this subject based on the ideXlab platform.

  • laboratory performance of unpaved roads reinforced with woven coir Geotextiles
    Geotextiles and Geomembranes, 2009
    Co-Authors: E A Subaida, S Chandrakara, N Sanka
    Abstract:

    Abstract The results of an experimental study conducted to investigate the beneficial use of woven coir Geotextiles as reinforcing material in a two-layer pavement section, are presented. Monotonic and repeated loads were applied on reinforced and unreinforced laboratory pavement sections through a rigid circular plate. The effects of placement position and stiffness of geotextile on the performance of reinforced sections were investigated using two base course thicknesses and two types of woven coir Geotextiles. The test results indicate that the inclusion of coir Geotextiles enhanced the bearing capacity of thin sections. Placement of geotextile at the interface of the subgrade and base course increased the load carrying capacity significantly at large deformations. Considerable improvement in bearing capacity was observed when coir geotextile was placed within the base course at all levels of deformations. The plastic surface deformation under repeated loading was greatly reduced by the inclusion of coir Geotextiles within the base course irrespective of base course thickness. The optimum placement position of coir geotextile was found to be within the base course at a depth of one-third of the plate diameter below the surface.

  • experimental investigations on tensile and pullout behaviour of woven coir Geotextiles
    Geotextiles and Geomembranes, 2008
    Co-Authors: E A Subaida, S Chandrakara, N Sanka
    Abstract:

    Abstract Results of an experimental programme to investigate the tensile and interface properties of woven coir Geotextiles are presented. Tension tests were conducted on coir fibres, yarns and woven Geotextiles at different gauge lengths and strain rates. Based on statistical analysis, a gauge length of 150 mm and a strain rate of 5%/min was adopted for the purpose of characterization of tensile properties. Tensile strength of woven coir geotextile was expressed as a function of fibre strength, yarn properties and weaving pattern. Pullout test and modified direct shear test were conducted on Geotextiles in granular soils of different grain sizes. At low normal stress, bond resistance of coir geotextile–sand interface obtained was more than shear strength of soil. But consistent values of bond resistance were not obtained at higher normal stresses. The opening size of mesh relative to the soil grain size influenced the pullout interaction between soil and geotextile. For closely woven Geotextiles, the pullout resistance did not vary much in soils of different grain sizes, whereas for Geotextiles with open meshes, pullout resistance obtained was more in fine sand compared to coarse sand.

E M Palmeira - One of the best experts on this subject based on the ideXlab platform.

  • opening sizes and filtration behaviour of nonwoven Geotextiles under confined and partial clogging conditions
    Geosynthetics International, 2017
    Co-Authors: E M Palmeira, H Trejos L Galvis
    Abstract:

    Nonwoven Geotextiles have been used as filters for over four decades in geotechnical and geoenvironmental works. These products have a complex fibre matrix and their behaviour as filters depends on how this matrix interacts with fluids and soil particles. Therefore, uncertainties still exist regarding prediction of geotextile filter performance under severe and critical situations. This paper investigates how confinement and partial clogging influence the dimensions of openings in nonwoven Geotextiles. Bubble point (BBP) tests were carried out on six nonwoven Geotextiles under unconfined and confined (equivalent vertical stresses of up to 1000 kPa) conditions with and without partial clogging of the geotextile. The results obtained show significant influences of confinement and partial clogging on geotextile opening dimensions and retention capacity. The results of O95 from bubble point tests on unconfined and virgin specimens compared well with results from hydrodynamic tests. Comparisons between BBP res...

  • tailings nonwoven geotextile filter compatibility in mining applications
    Geotextiles and Geomembranes, 2010
    Co-Authors: E M Palmeira, Elder A Beirigo, M G Gardoni
    Abstract:

    Nonwoven Geotextiles have been commonly used in filtration and drainage of geotechnical engineering works. This paper presents a study on the use of such materials in drainage and filtration systems of tailings dams. Different combinations of tailings and Geotextiles were submitted to gradient ratio (GR) tests under confinement in the laboratory with varying values of stress levels and hydraulic gradients. The results of GR tests under confining stresses up to 2000 kPa are presented and discussed. The dimensions of the tailings particles entrapped in the geotextile specimens and those that piped through the geotextile were also assessed. Geotextile specimens from the drainage system of a tailings dam were exhumed for analyses, as part of the research programme. The results obtained showed that stress levels and the hydraulic gradients used in the tests influenced the behaviour of the system. Physical and microscopic analyses of the specimens tested showed greater geotextile impregnation by tailings particles in the field than in the laboratory. The overall performance of the Geotextiles tested under laboratory conditions was satisfactory. However, in the field segregation of tailings particles and transport of fines in suspension can subject the filter to more complex and severe clogging mechanisms, not properly simulated in current standard testing procedures.

  • a study on biological clogging of nonwoven Geotextiles under leachate flow
    Geotextiles and Geomembranes, 2008
    Co-Authors: E M Palmeira, Aline F N Remigio, Maria Lucrecia Gerosa Ramos, Ricardo Silveira Bernardes
    Abstract:

    Abstract This paper presents results of long-term permittivity tests using leachate to evaluate biological clogging of nonwoven Geotextiles. Three types of Geotextiles with varying masses per unit area were used in the tests. The identification and quantification of microorganisms in the geotextile were carried out as well as microscopic investigations. The accuracies of semi-empirical models to evaluate the kinetics of bacteria growth and to correlate hydraulic properties and microbiological parameters were examined. Permittivity tests under increasing water heads were also performed on the geotextile samples already subjected to long-term leachate flow in order to evaluate the values of water heads required to wash the biofilms out of the geotextile pores. The results of the tests showed the marked reduction of geotextile permeability due to biological clogging and that the results of the predictions by semi-empirical methods were consistent with the biological mechanisms observed.

  • some factors affecting the in soil load strain behaviour of virgin and damaged nonwoven Geotextiles
    Geosynthetics International, 2007
    Co-Authors: M J A Mendes, E M Palmeira, E Matheus
    Abstract:

    This paper presents a study on the tensile response of virgin and damaged nonwoven geotextile tested in isolation under different conditions of confinement. Five Geotextiles, four confinement conditions and different types of mechanical damage were investigated. The influences of the intrusion of soil particles and the shape of these particles on the load–strain relation of the Geotextiles were also examined. The results obtained show that confinement reduces the detrimental effects of mechanical damage on the tensile behaviour of nonwoven Geotextiles. The amount and shape of the soil particles that intrude the geotextile pores also influence the tensile stiffness. The results show the potential of nonwoven Geotextiles as reinforcement for reinforced soil structures of low to moderate sizes where the use of stiffer reinforcements may not be necessary or may be cost-prohibitive.

  • drainage and filtration properties of non woven Geotextiles under confinement using different experimental techniques
    Geotextiles and Geomembranes, 2002
    Co-Authors: E M Palmeira, M G Gardoni
    Abstract:

    Abstract This work presents a study on the influence of stress level on some physical and hydraulic properties of non-woven Geotextiles relevant to drainage and filtration. Different types of tests were employed for the determination of geotextile thickness, porosity, permittivity, transmissivity and pore sizes under normal stresses ranging from 0 to 2000 kPa, depending on the type of test. Results of these different testing techniques were compared and their accuracy assessed. The increase of geotextile retention capacity caused by increasing stress levels and geotextile partial clogging was also evaluated, as well as the accuracy of equations for the estimate of geotextile permeability. The results obtained showed a marked effect of confinement on geotextile properties, with special reference to pore size diameters, with implications to current filter criteria for non-woven Geotextiles.