Thermal Cone Test to Determine Soil Thermal Properties

Abstract

A component of geotechnical applications involving nonisothermal conditions is the determination of the thermal properties of the ground. This paper presents a new test, called the thermal cone dissipation test (TCT), which overcomes most of the drawbacks observed in current in-situ techniques used to determine the thermal properties of soils. The equipment consists of a cone penetrometer equipped with thermocouples located behind the cone point. The TCT is pushed in the ground at the standard penetration rate of 2 cm/s, and the friction between the cone and the soil increases the cone temperature. The temperature decay is recorded as a function of time (for approximately 30 min) and this information is used to estimate the thermal conductivity and other thermal properties of soils. The calibration of the curves proposed in this work to estimate the thermal properties of the ground was based on three main activities: (1) in-situ experiments, carried out at three different locations involving different soil types; (2) laboratory investigation, aimed at obtaining the thermal conductivity of the soils studied in the field; and (3) numerical simulations, used to validate the proposed numerical models against the experimental data and to populate the proposed calibration curves including ground conditions to explore in the field. Very good agreements between field, laboratory and numerical results were obtained for the 11 TCTs studied in this research. It is expected that the proposed calibration curves will be enhanced in the future as additional experimental data become available.