Mechanical Response of the Liner in a Ring-Fractured Pressure Pipe under Bending Moments

Cured-in-place pipe (CIPP) has been widely used in pipeline rehabilitation as a trenchless, environmentally friendly and efficient repair technology. A three-dimensional computational model of the mechanical response of ring-fractured pressure pipe lining under bending moment is established by the finite element method, and the established model is verified by using the results of existing literature. The effects of parameters such as internal pressure, bending moment, outer diameter of the liner, liner thickness and friction coefficient between the liner and the host pipe on the stress of the liner are analyzed. The results show that: When the internal pressure exceeds 0.6 MPa, the maximum stress of the liner pipe is concentrated at the top of the ring section, and its radial displacement is only 0.24%~0.97% of the maximum displacement of the host pipe, indicating that the increase in internal pressure can effectively suppress the relative deformation of the liner and the host pipe. The length of the pipe section that generates stress in the liner increases linearly with the bending moment, outer diameter and thickness, but is suppressed by the internal pressure and friction coefficient. For example, when the friction coefficient increases from 0.1 to 0.6, the length of the pipe section that generates stress in the liner is shortened by about 30%, which provides a quantitative basis for the parameter trade-off in the design. At the circumferential position θ=90°, the stress on the inner surface of the liner exceeds that on the outer surface, and the difference becomes significant as θ increases.