Obtaining in situ thermal properties of soils is often difficult and time-consuming. Here, cone penetration test (CPT) correlations are proposed and validated for thermal properties of saturated ground, i.e. thermal conductivity and volumetric heat capacity, giving continuous profiles of the parameters, in a substantially reduced time. The proposed correlations utilise the characteristics of existing CPT correlations. The volumetric heat capacity correlations show good agreement with laboratory hot disc tests, and the thermal conductivity correlations proved successful for a range of soil types, including organic soils, clays and sands, although with a reasonable scatter. Empirical adjustment was required for the thermal conductivity of soils showing high (normalised) cone resistance. Utilising thermal CPT (T-CPT)-derived thermal conductivity point values in conjunction with the thermal conductivity correlations offers accurate and continuous site-specific profiles.

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The thermal cone penetration test (T-CPT) allows in situ measurement of the thermal properties of soil during a CPT-that is without withdrawing the CPT tool and introducing another tool such as a thermal needle probe. An interpretation method is presented based on one-dimensional axisymmetric analytical solutions. Numerical verification of the method is given and numerical simulations are presented to derive a calibration factor required for the interpretation model. This factor accounts for the temperature sensor location and two-dimensional geometric effects, particularly internal voids and end effects for the cone penetrometer. Finally field data are presented for the T-CPT and compared with results from in situ needle probe tests and laboratory tests on sampled material. The interpretation model is able to provide thermal conductivity values robustly.@en