In principle, there are two kinds of landfills, the dump-type and the pit-type. In the pit the seeping water must be piped to the shafts which are also placed in the waste. The effects on the shafts which are caused by the settings in the waste of up to 40%, destroy every normal shaft construction. Therefore the TNS developed the so-called telescopic shaft about 20 years ago. Here the individual shaft elements are stored flexibly and can move with the waste object.
Usually the shafts have a diameter of 2000 mm or more because the maintenance must be carried out in the shafts. On the bottom of the shaft there are pumps for the transport of the seeping water as well as the entrances to the lechate pipes which have to be cleaned in regular distances. The telescopic shafts allow construction heights of up to 100 m in the waste object. The landfill site Mechernich at Cologne is a reference in this extremely difficult installation case.
Nowadays our PROFILEEN® telescopic shafts are found in all pit-type disposals of the Federal Repuplic Germany and with the adaption of the European norms and quality standards more and more neighbouring countries also consider this innnovative product by planning the landfill sites. Telescopic shafts can also be integrated into the existing dumps later so that the quality of old landfill sites can be improved considerably. Such projects were carried out by us on a large scale in England in the last few years.
In principle at the dump type disposal only the drainage pipes are transferred into the waste object, the shafts are outside. Different to the pit disposal with waste heights of up to 100 m the dump usually reachs only a waste height of up to 20 m.
There is also the problem that in the waste highly aggressive seeping water arises from the rain which have to be piped away. Since the shafts are outside the sealing liner of the landfill site, the sealing has to be broken with the drainage pipes. Especially in this critical area high requirements on the safety are made because the pipe execution may not cause any leak in the sealing liner.
For this purpose the TNS has devoloped a special penetration building. On the one hand it is a transition from the drainage pipe to the collection pipe. On the other hand it is welded with the HDPE liner. Besides, this fitting has to take considerable static loads which are caused by the pressure of the waste object.
The collection pipes with the seeping water lead to each collection shafts. This serves to the imbedding of the pipes as well as an entrance for the camera inspection and cleaning of the drainage pipes. The static requirements on the shafts are rather little so that the conventional design as a rigid shaft can be chosen. As a rule, the construction heights of the shafts amount only up to 8 m.