Engineering Waterproofing Solutions For Underground Civil Infrastructure

Australia is fortunate to have built some of the driest tunnels in the world over the past 20 years with a very strong track record in achieving the highest specification requirement of ‘no damp patches’ over many hundreds of kilometres of tunnel construction. However, this hasn’t always been the case. In fact, early tunnels built in the 1980s and 90s suffered from severe water damage and cost contractors hundreds of millions of dollars in rectification works.

This paper will discuss how the Australian tunneling industry transformed itself by adopting international standards and a strong engineering approach to waterproofing solutions and details. We will review practices from other parts of the world, relevant standards, specifications and experiences using various membrane solutions.

Every tunnel project has its own unique circumstances and requirements which need to be considered during the design phase. Material selection in particular plays a key role in successful outcomes for waterproofing of underground structures. In this context we will review options for station boxes, shafts, caverns and TBM nozzles covering the benefits and limitations of various available materials. There is not a one-size fits all solution when it comes to tunnel waterproofing. We will analyse various projects completed over the past 20 years and the learnings from each of the different applications.

In more detail, the study will reflect on how our industry has managed to create dry cross passages locally, specifically in the most challenging area of terminating the membrane to the TBM segmental lining. We will investigate the engineering design of these terminations and how a robust solution, which is appropriate for underground applications, has been adopted.

With the confidence our industry now has in tunnel waterproofing, we will propose that an Australian Standard be considered with the development of a technical committee. A new local standard would be appropriate for local conditions and be reflective of the skills and knowledge that have been developed over the past two decades.