Solar Assisted Thermal Prefabricated Vertical Drains for Soft Ground Improvement of Sea Dikes

Preloading has been widely adopted in ground improvement engineering owing to its convenient construction and low cost. However, it is associated with long construction periods and considerable post-construction settlement. Thermal preloading consolidation mitigates the drawbacks of conventional preloading consolidation to a certain extent, and it can effectively reduce energy consumption by using solar energy. Therefore, this study investigates a solar-assisted thermal preloading consolidation technique incorporating innovative thermal prefabricated vertical drains (TPVDs). A field test of solar-combined TPVD system was conducted at a site in Taizhou Bay, China. Variations in soil temperature, pore water pressure, and settlement variation were monitored. Theoretical calculations and analyses of soil temperature, pore water pressure, and settlement were also conducted based on relevant thermal preloading consolidation theories. The test results demonstrate that the proposed technique elevates the average foundation soil temperature by approximately 3 °C. The daily average dissipation rate of excess pore water pressure reached 0.18 kPa/d for the heated group, compared with 0.14 kPa/d for the normal temperature group, indicating faster excess pore water pressure dissipation rate under thermal conditions. The total settlement was 13.57 mm for the heated group and 10.02 mm for the normal temperature group, indicationg an approximately 35% increase in settlement due to heating. This study provides a novel technical solution for soft ground improvement, with considerable theoretical value and practical engineering significance for enhancing the resilience of coastal infrastructure.