Hydraulic structures, such as shiplocks, are typically surrounded by backfills, leading to various contact interactions between the backfills and the outer surfaces of the structures. To investigate the evolution of contacts under different loading conditions across the entire structure and to explore the influences of contacts on stress distributions between the shiplock structure and soil, three-dimensional numerical analysis was conducted on the lock head of a shiplock, considering various loading scenarios and contact interactions. Results show that, the opening areas and displacements on the contact surfaces vary significantly during different phases of the construction and operation of the hydraulic structure. The entire process can typically be divided into pouring, backfilling, and water-filling phases, with the backfilling phase showing the largest opening displacement. Compared to calculations without considering the contact, the relative peak maximum principal stress can increase by up to 18.85% when the contact is taken into account, and its peak value is reached after the backfilling process being completed. The conclusions obtained in this study can offer the theoretical and practical references for the design of hydraulic structures and the assessment of their safety.