Effect of eccentricity and bonding on behaviour of sliplined pipe

Abstract

Sliplining is one of the trenchless technologies that can be used in the rehabilitation of an underground pipe. Typically the annular space between the host pipe and the liner is grouted. Common practice is to design the liner pipe to withstand full internal and external loads, without considering the structural contributions from the existing host pipe and from the grout. This over-simplified practice is followed partially because the behaviour of grouted sliplined pipes and the roles that the pipes and grout play in such a system are not well understood. This paper presents some insight into the behaviour of grouted sliplined pipes with the results of a numerical (finite element) analysis on the effects of eccentricity between the liner and host pipe and bonding at the pipe interfaces. This study shows that the direction of eccentricity between the liner and host pipe in a grouted sliplined pipe has a significant impact on the behaviour of the pipe with unbonded interfaces (a pipe-within-a-pipe system), or with bonded interfaces (a composite pipe). Vertical eccentricity (i.e. in the vertical plane) results in an increase in stress in the host and the liner pipe, whereas horizontal eccentricity results in an increase in stress only in the liner pipe. Sliplined grouted pipes with bonded interfaces are subject to less stress than pipes with unbonded interfaces. Furthermore, horizontal eccentricity has the effect of reducing the vertical ring deflection of pipes with or without bonded interfaces.