Physical modelling of thermal-cone penetration tests

In order to meet the requirements of precise design and high-quality development of shallow geothermal exploration and geothermal applications, a new in-situ testing technology is proposed for accurate and efficient estimations of both mechanics and thermal properties of soil layers by introducing the thermal-cone penetration tests (T-CPT). A CUMT type of heating T-CPT equipment and its testing method are then introduced. Considering the complex in-situ condition, a series of physical model tests are conducted to investigate the influences of heating time, penetration depth, soil density and moisture content on the thermal and mechanical responses, and therefore to look insights into the penetration and heat transfer mechanisms. The results of physical modelling indicate that 120s of heating time can reach the best heating efficiency of the probe, and the penetration at a larger depth with denser soil leads to a larger thermal conductivity after the back calculation. Additionally, the soil with larger relative density shows higher penetration resistance, whereas the increase of moisture content appears to decrease the penetration resistance.