appliedsciences Article  
Theoretical Study on Design of Composite Lining Structure with Rigid-Flexible Combination for Trenchless Pipeline Rehabilitation  
[PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 2, [PERSON] 1,* and [PERSON] 3  
Technless rehabilitation lining can be divided into flexible solid wall lining structures, rigid lining structures and rigid-flexible composite lining structures. This paper reviews the research status of the design theory of trenchless rehabilitation lining pipes, analyzes the theory of rigid-flexible composite lining structures, and points out that the value of the factor determined from non-grouting angle \(K_{1}\) is not clear in the design formula of the rigid-flexible composite lining structure mentioned in the ASTM 'Standard Practice for Installation of Machine Spiral Wound Poly (Vinyl Chloride) (PVC) Liner Pipe for Rehabilitation of Existing Sewers and Conduits (ASTM F 1741)'. The value of \(K_{1}\) was obtained by the numerical analysis method with MATLAB software. Through the analysis of the variation trend of the \(K_{1}\) value, it is concluded that the design formula in the ASTM standard is only applicable to the case of incomplete grouting filling between the original pipe and the lining pipe, and is not applicable to the composite lining pipe with complete grouting filling. Finally, the explicit formula of the non-grouting angle is obtained by fitting, which is more convenient to use. trenchless pipeline rehabilitation; rigid-flexible composite lining; structural design Article  
Theoretical Study on Design of Composite Lining Structure with Rigid-Flexible Combination for Trenchless Pipeline Rehabilitation  
Trenchless pipeline rehabilitation technology is a construction technology for the installation of lining pipes in existing pipelines, without excavation [1]. The commonly used trenchless pipeline rehabilitation technology can be divided into four categories. The first category is the repair process of inserting the lining pipe inside the pipeline based on the change in the physical properties of the pipe, including shrinkage lining repair technology, folding lining repair technology and in situ thermoplastic lining repair technology. The second category is the repair process of in situ curing lining inside the pipeline based on chemical changes in the materials, mainly including in situ curing lining repair technology, which can be divided into thermal curing, steam curing and UV curing, according to the curing type. The third category is the repair process of using profile or sheet material to install a flexible lining pipe inside the pipeline, and then filling mortar between the lining pipe and the original pipeline to form a composite lining, mainly including mechanical spiral wound lining repair technology, segment lining repair technology, gasket repair technology and short pipe lining repair technology. The fourth category is the repair process based on spraying molding, including resin spraying technology and mortar spraying technology. In the above repair processes, the first and second repair processes and the resin spraying repair lining in the fourth repair process belong to the flexible solid wall lining structure. The mortar spraying repair lining pipe in the fourth type of repair method belongs to the rigid lining structure. In the third type of repair process, mortar is needed to be filled and compacted between the lining pipe and the original pipe, so it belongs to the rigid-flexible combined lining structure. In previous studies, much research has been conducted on the design of flexible solid wall lining structures. Based on the linear elastic theory of small displacement, [PERSON] and [PERSON] [2] deduced the critical external pressure buckling strength formula of free rings according to the flexural differential equation of bending slender rods.