## 6 Conclusions and Discussion  
This study focuses on the dynamic evolution of the erosion of the seabed surrounding offshore structures, considering the differences in thermodynamic parameters of seawater and the seabed soil, and conducts theoretical research on the temperature rise in linear heat sources in water and soil media under a constant heating power. Based on this, theoretical research on the non-steady heat transfer principles in water-soil coupled media is carried out, exploring the theoretical basis and experimental verification methods for water-soil interface identification technology. The research results are of significant importance for improving the accuracy and reliability of sediment monitoring equipment, providing technical support for the operation and management of water transport engineering and offering theoretical support and guidance for the subsequent development of dock slope sediment equipment and the construction of monitoring systems. The main conclusions are as follows:  
1. The theoretical formula for the temperature change in a linear heat source in water with constant-power heating is derived. An analysis of iron and PVC heat sources under different seawater convective heat transfer coefficients shows that both materials quickly reach a stable temperature, independent of the material. However, as the convective heat transfer coefficient increases, the heat transferred to seawater rises, causing the stable temperature of the heat source to decrease logarithmically with the convective heat transfer coefficient. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Water**} & \multicolumn{3}{c}{**Soil**} \\ \cline{2-7}
**Time (s)** & **Theoretical** & **Experimental** & **Error (\%)** & **Theoretical** & **Experimental** & **Error (\%)** \\  & **Analysis** & **Results** & **Analysis** & **Results** & **Error (\%)** \\ \hline \(t=600\) & 40.0 & 34.5 & 13.8 & 44.6 & 36.3 & 18.7 \\ \(t=1200\) & 40.0 & 36.0 & 9.9 & 52.4 & 44.0 & 16.0 \\ \(t=1800\) & 40.0 & 38.3 & 4.3 & 58.1 & 49.8 & 14.3 \\ \(t=2400\) & 40.0 & 38.6 & 3.6 & 65.2 & 53.9 & 17.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The error percentages between the theoretical and experimental temperatures. 2. The theoretical formula for the temperature change in a linear heat source in soil under constant-power heating is derived. The temperature response of iron and PVC linear heat sources in eight types of clay and eight types of silt is calculated. The results show that PVC heat sources exhibit a higher temperature change rate than iron in the same soil. Heat transfer from the source to the soil is limited to about 0.2 m after 3600 s. As the heating power increases, temperatures of both PVC and iron sources rise, with a linear relationship between the final temperature and heating power after 3600 s, and the temperature difference between PVC and iron sources gradually widens. 3. The non-steady heat transfer laws of iron linear heat sources in water-soil coupled media are summarized, highlighting significant temperature differences between water and soil. A clear temperature gradient forms at the water-soil interface, which intensifies with higher convective heat transfer coefficients in water. In soil, slow heat transfer due to low thermal diffusivity results in a gradual surface temperature decrease in the heat source. Conversely, water's good thermal diffusivity allows for rapid heat transfer, leading to a faster surface temperature decrease. Monitoring surface temperature changes allows for analysis of temperature trends, aiding in distinguishing different medium interfaces and providing a solid theoretical basis for water-soil interface identification. 4. The indoor experiments validate the non-steady heat transfer laws for linear heat sources in water-soil media. Monitoring surface temperature changes and analyzing the temperature trends affirm the feasibility of water-soil interface technology based on these laws.