The method for waterproofing tunnels with KÖSTER products is based on a combination of negative side waterproofing and a liquid applied crack bridging waterproofing compound. The waterproofing layers cannot be infiltrated and the water will not move laterally between the layers as with membranes. The system does not need drainage. No water is being drained off the surrounding soil so the water table is not affected.
This system is suitable for tunnels built with shotcrete according to the New Austrian Tunnel Construction Method. Flowing water is stopped by injecting KÖSTER IN 7. Small leakages or whole walls which are being penetrated by water can be sealed with KÖSTER KD 2 Blitz Powder. To waterproof the entire surface from the negative side KÖSTER NB 1 Grey is applied to the dry and solid substrate. Active leaks are waterproofed with the KÖSTER KD System. This is followed by three layers of KÖSTER NB 4000 by spray application. Finally the system is covered with a reinforced shotcrete lining. The waterproofing is sandwiched between two concrete layers. This avoids water ingress and cracks larger than the crack-bridging system will only leak when it goes through both the inner and the outer concrete shell. In that unlikely case the crack can easily be detected and waterproofed with minimal effort.
Always adhere to the specifications in the respective Technical Guidelines. Also observe the local guidelines and standards.