# Characterization of the Evolution of Energy Loss Rate in Cyclic Load Testing of Marine Soft Soil
## 2 Test Materials and Programs
### Test Method  
To investigate the dynamic properties of marine soft soil, key parameters such as water content, dynamic stress ratio, and confining pressure were systematically varied and analyzed. The water content was adjusted to specific levels, and cylindrical specimens, measuring 140 mm in height and 70 mm in diameter, were prepared accordingly. Prior to testing, each specimen underwent K\({}_{0}\)-consolidation with a coefficient of earth pressure at rest (K\({}_{0}\)) of 0.7 for 24 h to simulate in situ stress conditions. The confining pressure was kept constant throughout the loading process. The tests were conducted using water contents of 40%, 50%, and 60%; surrounding pressures of 50, 100, and 200 kPa; and a cyclic stress ratio of 0.15. A stress-controlled loading method was employed, with axial dynamic loads applied in a sinusoidal pattern and precisely monitored via computer control to ensure accuracy and consistency. Prior to initiating the test, a static bias stress (\(\sigma_{\mathrm{s}}\)) was applied to each specimen for bias consolidation. Following consolidation, loading proceeded according to the test program, with sinusoidal dynamic stress applied to simulate tunnel traffic loading. Test termination was based on the number of load cycles: for specimens that remained intact during loading, testing ceased after 1000 cycles; for specimens that failed during loading, testing stopped upon failure. The test was conducted at a load frequency of 0.1 Hz. The dynamic stress ratio, defined as the ratio of dynamic stress to confining pressure, was halved due to the double-amplitude loading method. The test program is outlined in Table 2[14]. Figure 2 illustrates the relationship between the dynamic stress amplitude and axial strain of marine soft soil under different water content conditions and varying surrounding pressures. From the figure, the following observations can be made: (1) Effect of water content on the dynamic stress-strain relationship: At 40% water content, the strain range is small, and the distribution of dynamic stress amplitude is more centralized, indicating higher rigidity of the soil and lower deformation capacity. At 50% water content, as water content increases, the strain range expands significantly. This is especially pronounced under high perimeter pressure (\(\sigma_{\mathrm{s}}=200\) kPa), where the increase in dynamic stress amplitude is more evident, suggesting an increase in the soil's plasticity and a larger deformation capacity. At 60% water content, the strain range further expands, especially under high \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Specimen** & **Water** & **Surrounding** & **Deviator** & **Dynamic** & **Dynamic** \\
**Number** & **Content (\%)** & **Pressure (kPa)** & **Stress (kPa)** & **Stress (kPa)** & **Stress Ratio** \\ \hline CT-1 & & 50 & 22 & 15 & 0.15 \\ CT-2 & 40 & 100 & 43 & 30 & 0.15 \\ CT-3 & & 200 & 86 & 60 & 0.15 \\ \hline CT-4 & & 50 & 22 & 15 & 0.15 \\ CT-5 & 50 & 100 & 43 & 30 & 0.15 \\ CT-6 & & 200 & 86 & 60 & 0.15 \\ \hline CT-7 & & 50 & 22 & 15 & 0.15 \\ CT-8 & 60 & 100 & 43 & 30 & 0.15 \\ CT-9 & & 200 & 86 & 60 & 0.15 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Experimental plan and control parameters. perimeter pressure, with a significant increase in dynamic stress amplitude. The curve exhibits a regular loop, indicating that the soil may have entered a strong viscoplastic state, with a marked energy dissipation mechanism. (2) Effect of perimeter pressure: For all water content levels, the dynamic stress amplitude increases gradually with the rise in perimeter pressure. The stress-strain relationship under high perimeter pressure (\(\sigma_{\text{s}}\) = 200 kPa) is more complex, likely due to the interaction of effective stress and moisture between soil particles.