Design of Liners for Deteriorated Sewers - Latest Research to Make it More Efficient

Since the start of the Trenchless Technology industry, liners for deteriorated sewers have been structurally designed by applying Standards and methods that apply to flexible pipes installed by traditional trenching. It has always been known that there are large gaps in the logic of doing this, but in the absence of consensus on any alternative design method it has become the norm. 

The load carrying capacity of a flexible pipe requires consideration of its strength and the support it receives from its surroundings. The situation is more complicated for a liner as the deteriorated condition of the host pipe means that the support for the liner cannot readily be determined. 

This Paper details research to determine the load bearing capacity of grouted spiral liners installed in deteriorated gravity pipelines. The research aimed to quantify by how much grouting increases the load carrying capacity of a spiral wound liner compared to an ungrouted liner and also to an unsupported liner inside a rigid host pipe. 

The results of testing have shown that the effect of grout is far greater than previously considered. The implication of this work is that the cost and feasibility of structural renewal of pipelines can be greatly reduced. The research is particularly relevant to earthquake zones, and also allows more efficient design of liners for larger diameter pipelines.