WATERPROOFING/BTSYM WORKSHOP | TECHNICAL


Left:


Mined tunnel - Sikaplan synthetic sheet membrane barrier system


Left:


Cut-and-cover tunnel - synthetic sheet membrane system


in 1971. Recently, the tunnel was recognised as needing upgrades as per EU safety and security regulations. The remedial works to the tunnel provided Sika with the opportunity to inspect and test the membrane. Lab tests were conducted on 41 samples and the data plotted (see figure). Continuing the curve from the performance rate collected for 41 years, it can be seen that the PVC membrane would take far longer than 100-year durability to reach the designated 50% performance which indicated the end of its service life.


The first half of the workshop concluded with a


list of standards used for material and waterproofing requirements for geomembranes across Europe, with BS EN 13491:2018 (Geosynthetic barriers – Characteristics required for use in the construction of tunnels and associated underground structures) providing a harmonisation of these standards as well as providing guidance on testing. Reference was also made to the Austrian guideline (Tunnel Waterproofing, from ÖBV), published in 2015, covering closed tunnels (NATM and


December 2023 | 13


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