Large diameter reinforced concrete pipe redding design and installation in adverse soil conditions

This paper discusses and presents information obtained from studies completed on four large diameter gravity pipelines constructed in weak soils and high groundwater. Two of the reinforced concrete pipeline projects included pipe bedding designs that addressed the potential for poor installation conditions, while the other two appeared to be based only on the basic industry standard reinforced concrete pipe design methods. The pipeline designs that had contract documents that addressed the potential for poor installation conditions had minimal defects in the constructed pipeline. The projects that used the basic industry standards and did not address the potential failure modes of the poor installation conditions had considerable problems. These problems included joint seal failures, joint cracks, excessive settlements, excessive leakage and loss of design now capacity. The adverse soil conditions that were encountered in all four of the pipeline alignments included high groundwater, weak soils, perched water tables, and low permeability soils that were difficult or impossible to dewater. The primary focus of this paper will be to, 1) show the results of pipeline designs that do not address poor soil conditions, 2) show that industry standard design methods do not address poor soil conditions with respect to bedding and foundation design, and 3) to provide information that can be used to help address the potential problems associated with the design and installation of large diameter pipelines in poor soil conditions. alternatives are available and how to address the problem. In weak soils the designer must address the potential for excessive settlement and design a foundation and bedding system that will support the pipeline to be constructed. It is apparent that a design that does not address the failure modes related to poor installation condition will not serve the owner as desired and will have a life expectancy much less than expected.