ASTM Development Award to Rune Dyvik

This recognition acknowledges the extensive time and effort Rune Dyvik has dedicated in developing ASTM Standard Designation D8295 “Standard Test Method for Determination of Shear Wave Velocity and Initial Shear Modulus in Soil Specimens using Bender Elements.” These efforts on this standard are greatly appreciated by Committee D18.

The award was originally to be presented on June 29, 2020 at the Main Committee Meeting of D18 in Boston, MA, but due to the Covid 19 pandemic and associated restrictions the presentation ceremony has been postponed several times. The ASTM award was therefore shipped to Rune at this time.

Determination of initial shear modulus

The initial shear modulus, Gmax, of a soil is an important parameter for a variety of geotechnical design applications. For example, Gmax is needed to analyse and study the effect of soil-structure interaction in cyclic or dynamic loading situations, such as for earthquakes, wave loading and various sources of vibrations. The initial shear modulus is normally associated with soil shear strain levels of about 0.001% and below, for which Gmax is relatively constant and a maximum shear modulus value for a soil.

The piezoceramic bender element is an electro-mechanical transducer which is capable of converting mechanical energy (movement) either to or from electrical energy. The bender elements are installed in a variety of standard laboratory equipment types, for example triaxial, direct simple shear and oedometer devices. The transmitter element is mounted in the top cap and the receiver element in the pedestal.

During a test, the shear wave travel time from top to bottom of the specimen is measured by a digital oscilloscope or on a computer, resulting in a shear wave velocity for the soil specimen. Gmax is calculated from shear wave velocity and soil density. Bender element determinations of shear wave velocity are non-destructive. These measurements can therefore be taken at any stage of a triaxial, direct simple shear or oedometer test without interfering with the particular test itself.

The test method has been in use at NGI since 1985, but there has not been an established standard for how to conduct such tests, until now. See also link to PDF on the Bender element test.