Pipe materials are classified as either flexible (e.g. PVC, HDPE, ductile iron, steel, etc.) or rigid (e.g. concrete, vitrified clay, cast iron, asbestos-cement, etc.). The strength of flexible pipe is determined by pipe and soil stiffness (see Lusk_Flexible Pipe Design.zip). The strength of rigid pipe is determined by its crush strength and is usually evaluated in terms of the three-edge bearing strength or, in the case of ASTM C76 RCP, its D-load strength.
The purpose of this worksheet is to calculate crush strength, using the Marston Theory, for a single pipe (material & diameter), in a trench condition, with a superimposed wheel load. Lusk_Rigid Pipe Design – Range of Soil Cover.mcdx is intended for a complete system design where the cover on the pipeline varies from place to place. Lusk_Rigid Pipe Design – Single Case.mcdx is intended to evaluate a single location and is thus shorter and simpler to use.
This worksheet is built around ASTM C76 reinforced concrete pipe (RCP), mainly because that's the only rigid pipe I have used in the past 20+ years. However, this worksheet can be readily adapted to other types of pipe. Fill height tables for C76 RCP are available from the American Concrete Pipe Association and different manufacturers, but where is the fun in that?
* Both worksheets are in Mathcad Prime 3.0 format. For users with other versions of Mathcad, I have included Adobe Acrobat .pdf files for your viewing pleasure.