Behaviour of an interactive pipe liner under conditions that may occur following ring fracture of host main

Abstract

Renovation techniques such as use of liners to extend the lifetime of pipe networks are well established in the water industry. As well as spanning gaps and bridging holes, interactive liners are capable of surviving circumferential (or ring) failure, as may be experienced by distribution mains under flexural loading; movement of the host main following failure leads to tensile and shear displacements of the liner near the fracture. Experiments were carried out on cast iron host pipes containing a simulated transverse fracture, with thin-walled (∼3 mm) medium density polyethylene liners having a variety of longitudinal gaps. The fracture plane was subjected to shear displacements up to ∼50 mm and longitudinal separations up to ∼20 mm. Pipes were held at a pressure of 10 bar for about 12 days to allow creep deformation to take place, while the ability of the liner to withstand the applied displacement and separation was determined. It was demonstrated that the liner material investigated could withstand lateral deflections of the order of 50 mm for considerable periods of time. The implications of this finding on current design guidelines need further consideration. However, if the outcomes are favourable, this could lead to increased use of interactive liners, with potential benefits to both the water industry and the customer.