STP750

    Acoustic Emissions Generated During the Quasi-Static Cone Penetration of Soils

    Published: Jan 1981


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    Abstract

    As a rigid object is pushed into a soil, acoustic emissions are generated by soil grains sliding over one another, sliding over the penetrating object, and being crushed.

    In 1977, a research project was initiated to develop a system for recording such emissions generated during the quasi-static cone penetration of soils, and to evaluate their potential usefulness as a means for the in situ characterization of soils and soil deposits.

    In order to ensure knowledge of and control over all factors governing the engineering behavior of tested soils, all initial tests were performed in the laboratory. A field testing program has recently been initiated.

    Laboratory tests to date have been performed on a single graded sand. Variables included relative density, confining stress, and state of saturation. Analyses of the obtained acoustic records include the determination of peak-to-peak voltage, root-mean-square voltage, and frequency distribution analysis.

    Initial results indicate that:

    1. The resultant frequency distribution curves can be divided into two categories, one associated with lower confining stresses and penetration rates, the other with higher confining stresses and penetration rates, the other with higher confining stresses and penetration rates. These categories may well be signatures uniquely associated with the specific soil.

    2. The amplitude of the signal increases with penetration rate.

    3. The amplitude of the generated signal is larger in a dry, than in a saturated sample.

    The limited field tests performed to data indicate that amplitude of the generated signal may be used as an indicator of layering.

    The goal of the ongoing project is the development of a new method for the in situ identification and characterization of soils and soil deposits.

    Keywords:

    acoustic emission, acoustic signals, acoustic signatures, penetrometers, penetration, penetration resistance, soils, sand, amplification, amplitude, frequencies, frequency distribution, density (mass/volume), saturated soils, voltage gain, noise (sound), frequency modulated, tape recorders, evaluation, correlation, soil tests


    Author Information:

    Villet, WCB
    Research assistant, professor and chairman, and research assistant, University of California, Berkeley, Calif.

    Mitchell, JK
    Research assistant, professor and chairman, and research assistant, University of California, Berkeley, Calif.

    Tringale, PT
    Research assistant, professor and chairman, and research assistant, University of California, Berkeley, Calif.


    Paper ID: STP28347S

    Committee/Subcommittee: D18.14

    DOI: 10.1520/STP28347S


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