Longitudinal and circumferential bending moment responses of dislocated concrete pipes rehabilitated with CIPP liners under traffic loads

Abstract

Listen

Translate article

The dislocation of concrete pipe joints, caused by factors such as uneven settlement and surface loads, can lead to structural deterioration and even failure of the pipeline. Addressing how to repair such pipelines to enhance their disaster resistance and resilience is a critical issue. This study focuses on Bell & Spigot dislocated concrete pipes, conducting a full-scale model box experiment on the bending moment responses of dislocated pipes before and after Cured-In-Place Pipe (CIPP) rehabilitation under various burial depths. Additionally, a 3D finite element model was constructed to analyze the interaction between the dislocated concrete pipes and the surrounding soil, considering burial depth, load position, dislocated forms, flexural modulus of CIPP liner, and the liner thickness. A comparison of finite element (FE) model predictions and experimental measurements was made for CIPP liners at different burial depths, validating the reliability of the simulation results. Building on this, the study explores the influence of various factors on the longitudinal and circumferential bending moment responses of the dislocated concrete pipes before and after CIPP rehabilitation. Key findings indicate that at a burial depth of 0.5 m, the pipe experiences a deformation tendency with tension on the upper side and compression on the lower side. At burial depths of 1.0 m and 1.5 m, the pipe exhibits a deformation tendency with compression on the upper side and tension on the lower side. When the traffic load is positioned directly above the dislocated joint, the peak values of the longitudinal bending moments for the left pipe (P2) and right pipe (P3) adjacent to the dislocated joint increase by approximately 64 % and 137 %, and 74 % and 234 %, respectively, compared to when the traffic load is applied at the spigot and bell. The longitudinal bending moment of the pipe is significantly affected by both burial depth and dislocated forms, while the circumferential bending moment is primarily influenced by burial depth. At a burial depth of 0.5 m, the repair rates of the circumferential bending moments for the spigot and bell are higher than those at a depth of 1.0 m. When the dislocated form is BL, the circumferential bending moment repair rate for the spigot is the highest, approximately 0.52. When the flexural modulus of CIPP increases from 7000 MPa to 9000 MPa, the peak longitudinal bending moments in the midsections of P2 and P3 pipes decrease by about 15 %, while the longitudinal bending moment at the spigot of P2 pipe increases by approximately 22 %. Additionally, when the CIPP liner thickness is increased from 6.0 mm to 18 mm, the peak longitudinal bending moments in the midsections of P2 and P3 pipes decrease by 48 %, and the peak circumferential moments at the spigot and bell decrease by approximately 46 % and 17 %, respectively.