ABSTRACT
While spray-applied waterproofing membranes have recently been used in several large tunnelling infrastructure projects, the opinions about this approach remain polarized. This is not least due to varying experiences in terms of application and outcomes. There seem to be proponents who are predominantly focused on the simple and fast application method and the promising outlook of time and cost savings, and the opponents who deem the method sub-standard and too simple. Such extreme views are partially based on misinformation and misunderstanding, which are still prevalent in the industry. There is a place for these materials, but the limitations, constraints and implications which come with the choice of such a system need to be clearly understood. This includes the design approach for a membrane bonded to primary and secondary lining, consequently exhibiting some degree of composite action. And while the membrane and the secondary lining can be spray- applied, this process is not as fast and simple as it might appear. Based on experience, literature and case studies, this paper attempts to provide some clearer guidance on the capacity, implications, and limitations of a controversial material.
