Building Project - Sealing with Liner and Fleece

After the pudding-soft ground was stabilised, we had the rock which, of course, is totally unsuitable for placing the liner over. There is also the risk of the scree shifting and damaging the liner afterwards. We therefore installed another layer of Fleece900 topped with 5cm sand. On top of that we laid another fleece. This gives us a good safety distance between the liner and the stones.

While the ground was being reinforced, in other areas we started laying the liner.
We welded the 8m wide strips of liner with a special machine inside the excavation.

The NaturaGart pond sealing technology incorporates a self repair mechanism in case the liner gets damaged. The water flow takes ground particles to the leak and stops up the Fleece900 underneath.
To ensure that enough particles would be available we spread several tons of clay powder onto the first layer of liner.
On top of that followed a layer of Fleece900...
...and another liner, just in case.

Clay powder was extended over the liner which was then covered with a thin plastic foil. This helps to keep the construction site clean.
To protect against possible risks from above this layered seal was covered with another layer of Fleece900.
This way the two liners lie well protected between several layers of Fleece and are separated from the stones.
This way the two liners lie well protected between several layers of Fleece and are separated from the stones.

Protecting the liner from damage from above is crucial. Fleece alone is not sufficient to secure a 100 ton heavy cave construction.
For this reason the entire bottom of the pond was covered in a concrete layer. To this end a weave of 10mm thick structural steel rods was laid down - more than 50km in total.
The rods were then connected with tie wire every 20cm in about 50,000 places.
The structure covers the entire bottom and is reinforced in areas with greater loads.

The corners were reinforced. They distribute the load from the bottom to the terraces further up.
Rods of structural steel were prepared so that later the walls could be connected to the base structure.
One of the largest concrete pumps spread about 450m³ of concrete over the bottom. It has a range of 52m.

The concrete ground is not meant to seal the underwater park - that would be impossible. You can't built a 5000m² concrete slab without it cracking in numerous places.
The concrete exclusively distributes load. It ensures that the constructions on top will not create point loads. We even made ventilation holes to ensure that the water pressure above and below the slab are the same.  
During construction another problem arises 4m under the ground water level: Water keeps seeping in from the neighbouring terrain.
The liner seal with the concrete cover behaves like a ship in a dry dock: If the ground water level rises, the whole construction will float up.
It wouldn't survive this, of course. It'd break apart.
While building, therefore, the pumps ha to ensure that the ground water level would not endanger the construction. The height of the bottom was constantly monitored with laser bearings and checked with plummets.
Especially during the final construction phase the safety margins became ever slimmer. A failure in electricity supply of 2-3 hours could've spelt doom for the entire construction.

Please click here if you want to find out more about the NaturaGart sealing technology.