Validation and improvement of a punching test to ensure excavatability of cement-based materials used as pavement subbase

Cement-based materials, regularly used in urban road base layers, must be sufficiently resistant to traffic but above all, easily excavated, even with a pick, to allow easy access to the underlying networks during maintenance operations. Unfortunately, bibliography shows that there is no satisfactory method for determining the ease of excavation. This paper presents the results of a large campaign in which manual excavations and Charpy tests carried out on scale 1 trenches were analyzed with an original laboratory punching test. It proposes a rational definition of an excavation difficulty scale by linking the feeling of workers and excavated volume per pick impact. The latter can be calculated from punching test thanks a classic soil failure model. A complete methodology to determine at the laboratory stage the excavation difficulty with a pick is finally proposed, opening the way of rational optimization of excavation ease, while keeping the bearing capacity constant..