Proof Rolling Revisited

Proof rolling has been used as a technique to prove satisfactory foundation strength for earthworks structures for many years. It is a crude test, but effective in identifying obvious weak spots in subgrade soils that are predominantly of adequate strength to support embankments or pavements. However, problems can arise when proof rolling is inappropriately specified or the limitations of the test are not fully understood.

This paper provides an overview of the test method and its limitations. It also reviews some experiences where poor understanding of the test method has resulted in subsequent pavement failure or the construction of pavements that exceed design requirements.

A theoretical analysis of proof rolling deflections is provided for a range of subgrade soil strengths, under a specified proof roll loading nominated in AS3798. This analysis demonstrates the need to specify proof roll loading that is consistent with specific pavement design requirements rather than adopting a “one size fits all” approach.

Issues that need to be considered when specifying and performing proof roll tests are addressed.