SIDD pipe bedding and Ontario provincial standards

The current OPSS and OPSD that provide specifications for drainage pipes in Ontario, are shown to be a simplified and more conservative version of the traditional Marston-Spangler method. The SIDD method was developed through extensive finite element analyses. It improves the pipe installation practice by lessening the requirements in bedding and compaction, and allowing the use of native backfill materials. There is potential cost-savings in using the SIDD method. The SIDD standard adopted by ASCE/ANSI, however, seems to have missed a few important pieces of design information and is inconsistent with the original SIDD research publication in the definition of soil types. The paper shows that an improved version of the SIDD method should be considered for adoption as an alternative in the OPSS, while the traditional Marston-Spangler method is maintained in the standards. 2.1 Loads on buried pipe Design loads for rigid pipe have traditionally been determined using the Marston load theory (Marston 1930):