To accurately evaluate the forces and deformations of adjacent pipelines induced by shield tunnel construction, a Pasternak-TB mechanical model with piecewise uniform parameters is established. First, the pipeline is modeled as a Timoshenko beam on a Pasternak foundation. This model is then analyzed using a two-stage method to determine the forces and deformations induced by shield tunnel excavation. In the first stage, the additional load on the axis of the existing pipeline induced by tunnel excavation is calculated. In the second stage, a Timoshenko beam model on a Pasternak foundation with piecewise uniform parameters is established to simulate the pipeline. By applying the obtained load to this mechanical model, an analytical method for determining the pipeline forces and deformations is derived. Subsequently, the proposed method was validated against field data, existing theoretical methods, and centrifuge tests. Finally, the influence patterns of ground loss ratio and pipeline elastic modulus on pipeline forces and deformations were analyzed. Results indicate that the pipeline"s maximum displacement and bending moment increase linearly with the ground loss ratio. In contrast, an increase in the elastic modulus nonlinearly reduces the maximum displacement but increases the maximum bending moment. The proposed method provides an efficient tool for tunnel-pipeline interaction analysis; the revealed patterns offer a theoretical basis for ground loss ratio control and differential verification of pipeline strength.