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Maintaining the stability of the tunnel face during the construction of the submarine shield tunnel is the prerequisite for safe construction. A series of face instability model tests under saturated strata were carried out. The earth pressure, the evolution of the soil arch area and the amount of soil entering the soil groove caused by the instability of the tunnel face under different face water pressure conditions were studied. A series of numerical simulations were carried out to analyze the effects of tunnel face water pressure. The results show that the vertical earth pressure and horizontal earth pressure at different positions show a gradual decrease with the increase of the baffle backward distance, and the smaller the water pressure ratio, the more obvious this law is. According to the test results, the decrease of the water pressure ratio of the tunnel face can significantly increase the soil intake of the soil tank, which indicates that the collapse range above the tunnel face is large. The trend of instability region obtained by numerical simulation is consistent with the test monitoring results. This provides a reference for the construction of submarine shield tunnels. • Geomechanical model tests are carried out. • The pore water pressure and earth pressure are studied. • The evolution process of the soil arch area and the soil inflow volume of soil tank are investigated. • The failure areas is analyzed. [ABSTRACT FROM AUTHOR]