Cone penetration test with temperature measurement (Т-СРТ): analysis of the thermophysical interaction of the cone penetrometer with the soil

Introduction. The study of the Cone Penetration Test with Temperature Measurement (Т-СРТ) in the permafrost zone, as well as the interpretation of the obtained data for the purpose of determining the geotechnical characteristics of soils used in the calculation of bases and foundations, is associated with the solution of a number of scientific and technical problems. Aim. Development of a model and analysis of the thermophysical interaction of the “Т-СРТ probe – soil” system, taking into account the influence of various factors (soil type, condition and temperature soil, probing velocity, etc.). Materials and methods. A comprehensive empirical study of these factors is a highly complex task. Under these conditions, the development of adequate models of such interactions is particularly relevant. This paper presents the development of a model for the thermophysical interaction of a Т-СРТ probe with thawed and frozen soil during its penetration. For frozen soil, various relationships between frictional heat fluxes and phase transitions are considered, as well as its influence on probe temperature changes. Results. A model is proposed that explains and predicts the nature of Т-СРТ probe temperature changes during testing of thawed and frozen soils, taking into account probe and soil characteristics and probing velocity. The model explains the physics and conditions for the occurrence of the "pseudo-anomalous probe cooling effect" during testing of plastic-frozen soils. Conclusions. The thermophysical interaction of the Т-СРТ probe with frozen soil is more complex than with thawed soil. When testing plastic-frozen soils, the Т-СРТ probe temperature can not only increase but also decrease. The mechanical interaction of the probe with frozen soil should be considered in conjunction with their thermophysical interaction.