Progress toward a Unified Thrust Restraint Design—An Update

Widely varying material properties and joint configurations of the different pipe materials in common use have made it difficult to develop a coordinated thrust restraint design practice. This has resulted not only in significantly different guidance from AWWA design manuals for different pipe materials and agency requirements, but also widely varying design practices and company specific best practice approaches within the engineering community. Recognizing the need to develop consensus among practicing engineers as well as industry representatives and experts; in 2008, the members of the ASCE Technical Committee on Pipeline Installation and Location formed a special task committee "Thrust Restraint Design of Buried Pipelines". The objectives of this task committee were: 1) To document current design practices of thrust restraint systems for various pipe materials; and compare current practices with theory. 2) To document the historical evolutions of the different design approaches, collect and compile field tests completed for different pipe materials. 3) To explore improvements to current practice, develop consensus, and propose recommendations for the development of a manual of practice. Since 2008, the task committee has prepared a white paper documenting the above objectives, held a workshop on thrust restraint design at the 2010 ASCE Pipelines Conference, and begun preparing a manual of practice (MOP) with the aim of improving and consolidating current practice into a more cohesive, if not universal approach. The task committee has also presented several papers at the last three ASCE Pipelines Conferences, documenting findings and progress. This paper briefly summarizes the progress by the committee since its inception in 2008, focusing on the progress made by the committee since the 2011 Pipelines Conference. It includes updates on the progress toward developing an analytical model for thrust restraint that is intended to form the backbone of the MOP. The analytical model will include factors that deal with: pipe-soil interaction including frictional and lateral resistance, pipe and joint flexibility, movement required to develop soil resistance and the limitations of joint materials, type and geometry on movement induced by thrust forces. Both thrust block and restrained joint methods are included. A simplified approach for common applications is also proposed.