Comparison of German to Marston Design Methods

Abstract

In the United States and several other countries around the world, the Marston load theory is commonly used in computing the trench backfill loads on rigid pipes. Germany is using an alternative method developed by Abwassertechnischen Vereinigung e. V. (ATV) as the working design method for rigid and flexible pipe. This paper presents the German design method and a comparison of the two theories as they are applied to buried vitrified clay pipe design. The load ratio is defined as the ratio of the German load to Marston load. This ratio shows that the Marston theory is conservative for small pipes backfilled with well‐compacted granular material because it neglects the load relieving effect of the side fill and underestimates the friction between backfill soil and trench walls. The German design method is relatively simpler and could result in savings for vitrified clay pipe manufacture and design and for installation. The effects of the trench geometry, soil characteristics, the pipe diameter, and the stiffness ratio of bedding and backfill soils on the trench loads are studied in detail for both German and Marston methods of design. Results show that the load ratio depends significantly on the ratio of trench width to pipe diameter. This paper would be of great interest to engineers in pipeline practice in their attempts to evaluate design techniques used in other technologically competitive countries.