English
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JapaneseSustainability is achieved through less time for excavation, less handling of soil excavated from trench, less hauling of materials (both to and from construction sites), and reuse and recycling. This all means less energy consumption: In many cases, thes
Amster Howard
# 2021 Amsterdam
Deeper pipe burial, less expensive and environmentally friendly backfill, uniform language for contractors and inspectors, simplified installations for smaller pipe, and allowable construction in poor soil conditions are highlights in the latest edition of AWWA M55 and all benefit the users of HDPE pressure pipe. This paper summarizes the significant updates to the design and installation recommendations in the Second Edition of AWWA (American Water Works Association) Manual M55 PE Pipe – Design and Installation to be published in 2020. For design, these updates include higher Eʹ (Modulus of Soil Reaction) values, use of composite Eʹ values, use of Uniform Soil Classes, use of geotextiles, and terminology. For installation, there is revised information on trench width, flowable fill, inspection and soil testing, and compaction requirements. These changes reflect the recent revisions to ASTM D2774 Standard Practice for Underground Installation of Thermoplastic Pressure Piping. The changes are applicable to all pipe diameters and to all pipe stiffness values. The Second Edition of M55 encourages the use of basic installation and engineered installation for buried pressure PE pipe. The basic installation is for HDPE pipe stiff enough to not need special bedding and embedment, for shallow burial with no live load, and for stable trench wall support. In this case, the HDPE pipe can be laid on the trench bottom and backfilled with compacted soil from the excavation. This covers the majority of HDPE pressure pipe installations. For other conditions, the engineered installation means selecting an HDPE pipe and corresponding installation details to meet deflection, compressive strength, and buckling requirements. The engineered installation approachrecommends an uncompacted bedding and an uncompacted padding zone over the top of the pipe.
