Reappraisal of Marston’s Formula

A review of the genesis of Marston’s theory for soil loading of pipe in trenches found that the almost 90-year-old theory contains various flaws, including assumptions about lateral pressures and shear strengths that can be developed in trenches. The testing conducted at the time was found to be imprecise, raising questions that the findings may be spurious. The ensuing observations and evaluations of some of the pertinent parameters, including internal and side friction, and the use of Rankine’s formula suggest that faulty data were used to sanction the theory. The same factors that produced the false correlation apparently continue to permit engineers to design installations that in most cases are satisfactory. Some interim modifications to Marston’s formula are suggested to compensate for some of the discrepancies until further research is conducted and verified.