Defining a generic accelerated erosion testing method for earthen materials

Abstract

The 1952 CSIRO accelerated erosion test was the first to appraise the quality and potential longevity of earthen construction materials. The test measures the depth of erosion resulting from a spray of water delivered at a set pressure and distance from a nozzle of controlled geometry. The test has remained popular, due to its simplicity, and forms the basis of the design for durability in the current New Zealand earthen construction standards (and their derivatives). However, it is now recognised that the accelerated erosion test does not capture the full range of exposure conditions likely to affect an earthen structure during its lifetime. As such, academics and practitioners have suggested variations to the test, to reproduce erosion which is observed in the field. However, this makes it difficult to compare the results of one test to another, and so prevents any standardised material assessment. As earthen construction materials grow in interest in the unsaturated soils community, it is becoming necessary to understand and explore the limitations of these materials beyond their hydromechanical properties and to compare results between investigations fairly. This paper presents the concept of a ‘generic’ accelerated erosion test method and examines the effect of the spray pressure and spray distance on the erosive force delivered to the test specimen, to understand how these variables could be normalised. The generic method, when developed, will remove the strict restrictions of the original apparatus, making the test universally accessible.