Mechanical performances of the pipe-liner structure under void conditions

Voids still commonly exist around the pipeline after cured-in-place-pipe (CIPP) rehabilitation, posing a serious threat to the safe operation of the pipeline. However, current research primarily focuses on the improvement and performance evaluation of CIPP rehabilitation technology, with insufficient exploration of the impact of external voids on the pipe-liner structure. To address the aforementioned issues, this paper utilizes both full-scale tests and numerical simulations to investigate the mechanical performances of pipe-liner structures under void conditions by analyzing the effects of the void angle, depth and length on the stress state, differential displacement, relative rotation and bending moment of the pipe-liner structure. In addition, corresponding repair strategies were explored to provide practical solutions for addressing surrounding voids of the pipe. The results show that voids can reduce the interaction force between the pipe and the surrounding soil, alter the stress state of the pipe-liner structure, increase the vertical displacement and relative rotation of the pipe, and sharply increase the stress in the CIPP liner at pipe joints, with the effects becoming more pronounced as the void depth, angle, and length increase. Polymer grouting can effectively fill the voids around the pipeline, enhance the service performance of the pipeline, and provide an effective strategy for eliminating the effects of voids around the pipe.