Study of Mechanical Properties of Sand Layer Grouting Reinforcement under Seawater Erosion

Grouting serves as an effective method for mitigating geotechnical disasters in subsea tunnels. However, current theories and designs, primarily based on terrestrial tunnel contexts, seldom address the long-term effects of seawater ion erosion on reinforcement. An improved sand permeation grouting simulation test system was employed to examine the mechanical property evolution of sand layer grouting reinforcement under seawater erosion utilizing various grout types. The mechanical properties of grouting reinforcement, under varying curing conditions, were analyzed using a uniaxial compression test, permeability test, and scanning electron microscope (SEM) test. Test results indicate that seawater curing conditions initially enhance the strength and impermeability of grouting reinforcement; however, prolonged curing diminishes these mechanical benefits. The onset of this process occurs significantly sooner in cement-sodium silicate grout (28-56 days) compared to cement grout (56d to 90d). For the cement grouting reinforcement, the deformation modulus increases over time, albeit at a decreasing rate. The deformation modulus of cement-sodium silicate grouting reinforcement follows an increase-decrease-increase pattern, correlating with the volume ratio over time. The decline in mechanical properties of grouting reinforcement during the test's mid to late stages under seawater conditions results from the interplay between erosive ions, which inhibit mechanical growth and accelerate deterioration.