Bbnt Solutions Llc.

Bbn Corporation

William R Hamblen

Evan Frank Berkman

Estelle Watters

Frank Berkman

Bill Watters

An apparatus and method are provided for the in-situ measurement of the stiffness of a layer of soil or other surface of interest. The apparatus includes a contact foot for engaging the surface and a drive transducer coupled to the contact foot for applying a vibratory force to the contact foot in response to a drive signal. A motion sensor is coupled to the contact foot and in a preferred embodiment an additional sensor measures the force applied to the contact foot and hence to the surface. These sensors generate corresponding output signals. The output signals are used to generate a measurement signal that is representative of the surface stiffness.

Soil compaction measurement

The in-situ measurement of the shear modulus of a surface layer of soil ( ) is performed by apparatus in which a contact foot ( ) with a preselected downward bias force engages a defined area of a region of soil. A drive transducer ( ) shakes the contact foot ( ) vertically and sensing transducers ( ) determine the force applied to the foot ( ) and the resulting movement of the foot ( ) and generate respective first and second output signals. The in-phase movement responsive output signal is analyzed in relation to the force signal to obtain a measurement of a single parameter which is representative of the stiffness provided by the soil ( ). The shear modulus as well as the void ratio of the soil can be calculated from the stiffness. The drive transducer ( ) is energized by an a.c. signal which progressively varies in frequency over a preselected band with the rate of change also varying with frequency thereby providing a greater force spectrum content at lower frequencies than at higher frequencies in the band, while maintaining a substantially constant force magnitude.

Growing community of inventors

Stow, MA, United States of America

William R Hamblen