Abstract: The influence patterns of frost heave effects caused by shield connection freezing construction are the basis for evaluating the stability of adjacent tunnels and formulating countermeasures, while the constraint state of the surrounding strata on tunnel structures directly determines the distribution characteristics of the frost heave effect. Based on the large-diameter shield underwater connection project, the model tests of freezing reinforcement under two extreme boundary conditions of constant load free movement and fix constraint of the tunnel structure are designed and carried out. The evolution patterns of strata temperature, frost heave force and displacement during the freezing process are investigated, and the mechanical response and displacement change process characteristics of the adjacent tunnel are obtained. Under the condition of scattered boreholes on the outside of the shield, all the space between the freezing pipe and the shield is completely frozen after 70 days of freezing, and the thickness of the frozen wall at the shield connection position could reach 6 m after 165 days, with an average temperature of about -16.1℃. The maximum frost heave displacement of the adjacent tunnel during the formation of frozen soil outside the shield is 9.6 mm, and the maximum increase of the frost heave force acting on the tunnel surface is approximately 14.1% of the stratum's original pressure. The compression deformation and dispersion effect on frost heave force of the unfrozen stratum between the frozen soil and the tunnel are the key factors affecting the tunnel structure's ability to withstand the frost heave effect. The average deformation modulus of the unfrozen stratum slightly increases with the expansion of the frozen soil, and the average deformation modulus of the silty clay stratum is between 20.8 and 49.3 MPa. The research results indicate that the constraint state adjacent to the tunnel significantly influences the process of frost heave displacement and the variation in the borne frost heave force. Meanwhile, the compression process of the unfrozen stratum absorbs part of the frost heave effect, thereby reducing its impact during construction.