Predicting Hydrostatic Infiltration in Reinforced Concrete Sewer Pipes Considering Joint Gap and Joint Offset

Abstract

Groundwater infiltration into underground sewer systems has long been a costly issue for municipalities. With reinforced concrete pipe (RCP) being a primary sewer system option, existing hydrostatic testing methods conducted by manufacturers, as required by specifications, do not reflect real in situ hydrostatic performance. This paper deploys the results of a novel experimental approach, which better simulates field conditions, for evaluating the resistance against infiltration of RCP with joint imperfections. The hydrostatic infiltration test developed is safe and easy to conduct by RCP producers at the factory. A total of 68 tests were conducted on full-scale 600, 900, and 1,200 mm diameter RCP with various joint gap and joint offset alignment conditions using two models of single offset self-lubricated gaskets that are commonly used in jointing RCP. Experimental hydrostatic infiltration performance curves were developed, indicating that predictions of the sealing potential derived using gasket geometry agreed with the results of the infiltration test. Results demonstrated that reasonable prediction of the infiltration resistance potential of joint gaskets could be achieved. An infiltration potential assessment procedure pertinent to the test results and field conditions was presented. A case study of deep RCP pipe subjected to groundwater pressure was provided to illustrate the usefulness of the performance curves to derive maximum allowable joint gap, which contractors could rely on during RCP installation. The findings should provide technical guidance on how water tightness of RCP can be achieved at installations below the prevailing groundwater level.