Application of the Heat Flow Cone Penetration Test to measure the thermal conductivity of offshore soils

Master thesis (2022)

Authors

L. Vrielink Civil Engineering & Geosciences

Contributors

P.J. Vardon Geo-engineering - CEG (supervisor 1)
Alexandros Daniilidis Reservoir Engineering - CEG (supervisor 2)
M. Murali Fugro (supervisor 2)
Faculty
Civil Engineering & Geosciences
Copyright: © 2022 Leon Vrielink
CPT Offshore HF-CPT Thermal Conductivity Volumetric Heat Capacity Soil Investigation
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Published Date

06-12-2022

Language

English

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Faculty

Civil Engineering & Geosciences

Abstract

Interpretation of the thermal properties of soils is an important challenge in the field of geo-engineering, for example the development of geothermal energy solutions and for the design of electricity cable routes used for offshore wind farms. Of the thermal properties, the thermal conductivity is of most interest to find, as this determines the long-term thermal response of the soil. The soil volumetric heat capacity is of secondary interest, as this mainly influences the short-term thermal response.

To find the thermal properties of offshore soils, a new in-situ test is being developed, called the heat flow cone penetration test (HF-CPT). This test uses a module that can be attached to a cone penetration test (CPT) which contains a heating element and temperature sensors. In this test, the penetration trough the soil is stopped at a required depth, the heating element is then activated, and the thermal response of the probe is measured. This thesis presents an interpretation method that can predict the thermal conductivity of soils based on the thermal response of the HF-CPT. The interpretation method is validated by conducting laboratory tests in four different materials: moist sand, saturated sand, kaolin clay and a water-agar mixture. With the interpretation method, excellent results are found with the laboratory tests conducted in saturated sand, kaolin clay and the water-agar mixture.

The interpretation method is suitable for offshore testing, as the runtime of the method is short and the storage space is low. The interpretation method gives an accurate prediction for testing duration of about 300 seconds, which is fast when compared to other in-situ tests to measure the thermal conductivity of the soil. With this interpretation method, the HF-CPT can become a successful new in-situ test to determine the thermal conductivity of offshore soils. This way, the thesis contributes to the implementation of geothermal energy solutions and offshore cable routes for wind farms.