Three-Component Approach: Double-Layer Pressurized Waterproofing System With Planned Block Backing
The “three-component approach” for high waterproofing requirements is a new waterproofing system especially for high water pressures. It is presented here as a possibility that can be implemented in construction practice. A geosynthetic clay liner (GTD – or bentonite mat) is installed as the first layer behind the 3 mm thick tunnel sealing membrane that retains water under pressure, instead of the usual protective and drainage geotextile. Laboratory tests as well as practical application on the tunnel construction site show that the use of bentonite mats and plastic sheet membrans (PSM) as a double-layer pressurized waterproofing with simultaneous extended ridge gap injection (block backfill) is a promising alternative to the double-layer system with PSM and could represent a new state of the art.
1 Introduction
New tunnel constructions increasingly pass through ecologically sensitive areas, and the requirements for groundwater protection are increasing. Often, the permanent reduction of mountain water is not approved for ecological reasons. In these cases, tunnel structures must be formed against pressurised water, i.e. for high water pressures. However, the higher the water pressures rise, the more demanding are the requirements for tunnel sealing systems.
At the same time, increasingly complex tunnel sealing measures have to be implemented on the construction site. For water...
