Evaluation of Excavatable Cement Treated Materials for Urban Areas

For networks owners, like the French national gas utility, it is essential to ensure a rapid access to their installations, even with a simple pick, for normal or emergency maintenance matters. Modular concrete pavements were developed during the last years for that purpose. In order to keep their stability, the concrete elements are laid on a base made of cement treated material. With this concept, the pieces on the surface are designed to be easily removed but the base material must be excavated with light equipment as well. On the other hand, and whatever the base layer is made of, self-compacting materials with low cement content could be used more widely for back-filling of urban trenches because they don’t need mechanical compaction and so require less wide trenches. But as for the first case, the dissemination of the so called Controlled Low Strength Materials is hampered by the need to ensure their excavability for further maintenance. Yet, current available classification systems or empirical criteria appear to be inefficient to estimate accurately if a cement treated material can be easily excavated. In this context, Ifsttar and the French national gas company, are developing a new approach based on an original laboratory punching test validated on field excavation tests. The paper first presents the context and the issues of the research. Then it describes the new tools developed and a large experimental campaign comparing laboratory data and in-situ test results. Finally, a model based on the punching penetration test which allows the prediction of excavated volumes for a given energy is presented and applied to the results. The paper concludes on the relevance of the developed method and on the interest of the punching test to characterize excavatability.