Improving anchor-staying capacity in offshore environments by means of thermal consolidation

1. Home
2. Publications
3. Online Library
4. Improving anchor-staying capacity in offshore environments by means of thermal consolidation

Thermal cycles in normally and slightly overconsolidated clays can lead to permanent contraction that contributes to the improvement of their mechanical properties.  Specifically, thermal consolidation leads to an increase in undrained shear strength of marine soils which will help improve the pullout capacity of offshore foundations and anchors, a matter of interest for the oil and gas industry. On the other hand, traditional techniques for onshore soil improvement cannot be applied under ultra-deep water conditions. Thus, the use of the torpedo pile itself as a heat source was studied in order to promote the thermal improvement of the marine clay that comprises most of the Brazilian seabed soil. The study was carried out using reduced-scale physical models consisting of a thermal torpedo pile that was heated to provide thermal consolidation of a surrounding clay layer. Three reduced scale models were tested in a geotechnical centrifuge at 20g: one without heating and the other two where a heating-cooling cycle in the torpedo pile was applied. The maximum temperatures for the two heated tests were 45°C and 65°C respectively. The improvement in undrained shear strength was assessed using T-bars tests simultaneously carried out at four different distances from the heat source (torpedo pile). During heating, the soil temperature at different depths, pore water pressure and displacements were monitored. Due to the temperature increase, a heat bulb was initially generated around the pile, accompanied by an increase in pore water pressure, which was dissipated subsequently. After the pore pressure dissipation, the soil was cooled down and T-bar penetrometers tests were carried out in order to assess the undrained shear strength profiles of the soil and compared to those obtained from the test carried out without thermal treatment. Notable increases in undrained shear strength were observed in both heated tests for distances up to four times de pile diameter. Thus, it is believed that this procedure can be used as a promising technique for improving the torpedo pullout capacity in deep water environments.

5th European Conference on Physical Modelling in Geotechnics (ECPMG2024)

Onshore and offshore foundation systems