On measuring the bulk shear properties of superphosphate fertilizer

Abstract

A review of the theory of the shear testing of granular materials is given, together with a discussion of the requirements for test specimens and equipment. The theory of the annular cell is also reviewed and a computer programme to solve the Hvorslev equation for true stress is developed.

The physical properties and yield loci for fourteen instantaneously compacted granular superphosphate samples are presented. Stresses calculated on the assumption of uniform strain were within 5% of the true stress. No significant regression existed between the shear stress during compaction and that during the test which followed it.

The flow characteristics of samples representing approximate extremes in particle size and maturity indicate that these materials are free flowing.