Response of Repaired Sewers Under Earthloads

Abstract

The trenchless rehabilitation of damaged rigid sewers has become a competitive alternative to conventional methods of pipeline replacement. However, buckling caused by fluid load is identified as the important limit state in the current pipe-liner design standard, while the contribution of the damaged rigid host pipe in the assessment of resistance to earth loads as well as disturbance to the liner (e.g., vehicle loads) is neglected. Fullscale testing in the laboratory is used to investigate the soil–host and pipe–liner interaction. Two host-pipe–liner systems are examined. The first system involves a liner that fits perfectly inside a host pipe. The second system features initial lack of fit between the liner and the host pipe, and gaps across the fractures in the host pipe, to investigate ungrouted repair of rigid pipe with severe damage. The test geometry and measurement scheme to evaluate local bending and movement at the fractures in the host pipe are described. Key parameters affecting local bending are identified, including initial lack of fit between the liner and the host pipe as well as the hoop stiffness of the host pipe. This recent research on repair of sanitary and storm water sewers is discussed in the context of culvert rehabilitation.