Standard Test Method for Determination of Shear Wave Velocity and Initial Shear Modulus in Soil Specimens using Bender Elements

Importancia y uso:

5.1 The initial shear modulus (G_max) of a soil specimen under particular stress and time conditions is an important parameter in small-strain dynamic analyses such as those to predict soil behavior or soil-structure interaction during earthquakes, explosions, and machine or traffic vibrations. G_max can be equally important for small-strain cyclic situations such as those caused by wind or wave loading. Small-strain G_max is also vital for non-linear analyses of large strain situations, where the larger strain soil stiffness results could come from torsional shear tests, for example. Shear wave velocity and G_max can be used to compare different soil specimens in a laboratory testing program, and also for comparing laboratory and field measurements of these parameters.

5.2 Torsional resonant column tests (Test Method D4015) are often used to determine properties of a soil specimen at small shear strains up to and possibly slightly beyond 0.01%. Resonant column test results can include G_max versus time, shear modulus versus strain, damping ratio versus time and damping ratio versus strain. Bender element tests can only provide the first of these, G_max versus time. The strain level in bender element tests is small (constant G_max strain levels), but the strain magnitude is not known and the strain is not constant along the shear wave travel path due to material and geometric damping. Bender elements can therefore not be used to evaluate shear modulus versus strain and do not provide information about damping ratio. However, bender elements can be incorporated in a variety of different laboratory testing devices, allowing the measurement of small-strain and large-strain stiffness on the same specimen at the particular conditions of the test and possibly eliminating the need for additional resonant column tests.

Note 1: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.

Subcomité:

D18.09

Volúmen:

04.09

Número ICS:

13.080.20 (Physical properties of soils)

Palabras clave:

bender elements; Gmax; Go; initial shear modulus; shear wave velocity; triaxial test;