Piezoelectric probe for measurement of soil stiffness

Measurement of in situ soil properties is imperative for pavement design. The stiffness and Poisson's ratio of base and sublayers are essential factors in the design and quality control of compaction during construction of highway pavements. It is critical to have a portable and mechanised system to measure these parameters in situ. Currently used techniques including California bearing ratio, resilient modulus, dynamic cone penetrometer and falling weight deflectometer have limitations preventing compliance with requirements for the design of highway pavements. A new device implementing a geophysical probe equipped with piezoelectric sensors to measure the soil properties has been developed. Initial laboratory testing has been performed. The techniques for measuring soil stiffness are discussed, emphasising bender and extender element applications. Data acquired from the new device are compared with the results of an empirical formula developed by Hardin and Richart. Representative test results demonstrating the device performance are discussed.