An Experimental Technique for Determining the Hydraulic Properties of Unsaturated Pyroclastic Soils

    Volume 33, Issue 4 (July 2010)

    ISSN: 0149-6115

    CODEN: GTJOAD

    Published Online: 15 June 2010

    Page Count: 23


    Nicotera, Marco Valerio
    Assistant Professor, DIGA—Dipartimento di Ingegneria Idraulica, Geotecnica ed Ambientale, Univ. di Napoli Federico II, Napoli,

    Papa, Raffaele
    Research Assistant, DIGA—Dipartimento di Ingegneria Idraulica, Geotecnica ed Ambientale, Univ. di Napoli Federico II, Napoli,

    Urciuoli, Gianfranco
    Associate Professor, DIGA—Dipartimento di Ingegneria Idraulica, Geotecnica ed Ambientale, Univ. di Napoli Federico II, Napoli,

    (Received 2 October 2009; accepted 28 April 2010)

    Abstract

    The experimental technique proposed in the paper was designed to rapidly and reliably determine both the water retention curve and the permeability function of undisturbed natural pyroclastic soil samples. The technique was developed in the framework of an experimental research project on mudflows in pyroclastic soils in the southern Italian region of Campania (Italy). Grain-size distribution and void ratio of the particular pyroclastic soils suggested investigation of the hydraulic behavior for matric suction values in the range between 0 and 100 kPa. Our experimental technique consisted of a sequence of testing phases to be conducted on a single undisturbed soil sample: A constant head permeation test, a forced evaporation test, and finally a drying test in a pressure plate apparatus. Interpretation of the experimental data was based on inverse modelling and allowed both water retention curves and permeability functions to be determined. The six parameters of the Mualem–van Genuchten model were adopted to describe the hydraulic behavior of the tested soils. Each testing phase supplied experimental data to be used in the interpretation procedure: The permeation phase provided a matching data point for the permeability function near saturation; the forced evaporation test was related to the hydraulic behavior for matric suction values ranging from a few kPa to less than 80–90 kPa (i.e., mini-tensiometer functioning range); and the drying steps in the pressure plate apparatus provided information about the retention properties for matric suction values up to 1 MPa. The results shown in the paper clearly confirm the goodness of the experimental design and the interpretation procedure.


    Paper ID: GTJ102769

    DOI: 10.1520/GTJ102769

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    Author
    Title An Experimental Technique for Determining the Hydraulic Properties of Unsaturated Pyroclastic Soils
    Symposium , 0000-00-00
    Committee D18