Understanding the mechanical changes of marine soft soil under temperature is crucial for the construction and long-term operation of submarine pipelines. A series of basic physical and mechanical properties tests was carried out on the marine soft soil in Shanwei

Guangdong province. X-ray diffraction

X-ray fluorescence spectrometry

and scanning electron microscopy were employed to achieve the marine soft soil’s mineral composition

element composition and microstructure. The consolidated undrained laboratory tests under isotropic consolidation and biaxial consolidation conditions were carried out using a temperature-controlled triaxial apparatus. The test results revealed significant findings. Firstly

when the axial strain is small

the undrained shear characteristics of saturated marine soft soil are influenced by the ambient temperature and the consolidation stress ratio. Specifically

a higher ambient temperature or a smaller consolidation stress ratio results in a greater secant modulus. The secant modulus exhibits an inverse relationship with the consolidation stress ratio and demonstrates a power function relationship with the ambient temperature. As the axial strain increases

the peak strength of the soil is affected by both ambient temperature and consolidation stress ratio

while the peak pore pressure is less affected by ambient temperature. Furthermore

the initial dry density of the sample was found to impact the undrained shear characteristics of the isotropic consolidated soil (K=1.00). A greater initial dry density resulted in a smaller peak pore pressure

a greater peak strength

and a more significant decrease in peak strength with rising temperature. Additionally

the consolidation stress ratio was observed to affect the peak strength and effective stress path of saturated marine soft soil under different ambient temperatures. Specifically

when K=1.00 or 0.67

an increase in the ambient temperature softened the saturated marine soft soil; whereas when K=0.50 or 0.40

the rise in ambient temperature hardened the soil.