Study on bearing capacity of corroded pipes before and after spraying rehabilitation

Abstract

In recent years, there has been growing interest in trenchless technology, particularly in using centrifugal spraying technology to rehabilitate drainage pipelines. In this study, we evaluated the effectiveness of fiber-reinforced cement mortar spraying materials on pipes using the three-edge bearing test (TEBT) as per ASTM C497 standards. Six conditions of corroded and rehabilitated pipelines were tested: (1) corrosion depths, (2) corrosion widths, (3) corrosion positions, (4) pipe diameters, (5) loading rates, and (6) repair thicknesses. Through the TEBT, the structural bearing capacity and failure form of the pipe before and after repair were compared, and the bearing capacity difference of the pipe under different conditions was studied. Finally, a sensitivity analysis was conducted on the six variables. Among the many factors that affect the reliability of pipe structures, the influence degree of each factor is quite different. Through the parameter sensitivity analysis, the influence degree of each factor on the reliability of the structure can be clarified. The results show that the bearing capacity of the rehabilitated pipes is sufficient to meet the normal pipe bearing capacity requirements. The mortar lining and existing pipes can bear stress jointly, significantly increasing the maximum load of the rehabilitated pipes by up to 55.6 % and correspondingly reducing the circumferential strain. This indicates that the application of the mortar spraying lining layer effectively achieves the purpose of pipeline repair. This study provides valuable guidance for structural design optimization and safe operation.