Determining the wall thickness of flexible polymer liners for the rehabilitation of pipelines of the state class I

Summary

The wall thickness is one of the main parameters that determine both the service life of a gravity sewer pipeline subject to rehabilitation with the use of flexible polymer liners, and the economic efficiency of repair and rehabilitation activities. The wall thickness of a flexible polymer liner is determined based on a static calculation with the algorithm depending on the condition of the pipeline subject to rehabilitation and the loads acting on it. At present, special software developed by foreign companies is used to calculate the wall thickness of a flexible polymer liner. A method for static calculation of flexible polymer liners cured inside a pipeline is proposed that while using tables and graphs allows determining the liner wall thickness during the rehabilitation of a state class I pipeline, provided the main load acting on the «new polymer pipe – pipeline» system is groundwater pressure.

Key words

pipeline , water disposal system , rehabilitation , flexible polymer liner , static calculation

Determining the wall thickness of flexible polymer liners for the rehabilitation of pipelines of the state class II

Summary

Once gravity sewer pipelines are put into operation, longitudinal cracks may appear in the pipes after a relatively short period of time caused by the low quality of pipe products and violation of the construction technology. Pipelines with longitudinal cracks (state class II or III) can be rehabilitated using flexible polymer liner, provided that the «pipeline – soil» system is statically stable. A method for estimating the static stability of the «pipeline – soil» system is given. Taking into account the properties of the soil, backfilling and ovalization of the pipeline, the main loads acting on a new polymer pipe during the rehabilitation of pipelines with longitudinal cracks (condition class II) are determined. An algorithm is proposed for calculating the wall thickness of a flexible polymer liner for the rehabilitation of pipelines of the above-mentioned state class depending on the actual loads. As an alternative to using foreign specialized software, a method is proposed for calculating the wall thickness of a flexible polymer liner that provides for using tables and graphs to determine the wall thickness of the liner for the rehabilitation of state class II pipeline on exposure to the soil pressure, groundwater and transport loads.

Key words

pipeline , water disposal system , rehabilitation , flexible polymer liner , static calculation

Specific features of the static calculation of underground pipelines of gravity wastewater disposal systems

Summary

An essential pre-requisite for environmentally safe and reliable operation of underground pipelines of gravity wastewater disposal systems is specifying the requirements for the structural behavior of building construction elements (pipes, fittings) that are determined on the basis of a static calculation of the pipeline. In the process of the static analysis, direct and indirect loadings acting on the pipeline are determined and analyzed, and their impact on the structure is estimated. Existing approaches to performing a static analysis are considered. Based on the results of the studies carried out by Russian and foreign authors, it has been argued that the choice of the pipe parameters used in the construction of underground pipelines depends not only on the properties of structural materials, but primarily on the soil properties, conditions of laying and installation, as well as on the existing loadings and degree of pipeline deformation.

Key words

water disposal , underground pipeline , method , static calculation , trench , pipes , back filling