Context: We perform a lot of CFD (Computational Fluid Dynamics) modelling for our clients (geothermal, construction, general underground engineering, etc) where we have to model temperature flows and changes in a soil medium. In this type of modelling small changes in the thermal conductivity value of the soil medium have dramatic effects on the results of the model.
We've identified inaccuracies in our model's soil thermal conductivity value (when compared to the actual thermal conductivity of the real-world soil we are trying to model) as one of the primary sources of error in our models.
Question: What is the most accurate method for estimating the thermal conductivity of a target real-world soil, besides costly direct physical measurement? We can generally get estimates of many soil properties for our target soil from geo-tech studies, such as texture, carbon, rock content, etc. so these can potentially be used as inputs.