With creaking tracks and maxi- mum effort the excavator started to move backwards and the first layer of concrete crumbled and fell aside. Then the anchor bolts of the rails broke with a loud noise and the first centimetres of track whe- re visible behind the opening of the adapted bucket. Using huge cutting discs and to prevent the wholesale destruction of the road, the construction firm of Tschirren had previously cut a 500 millimet- re deep slit in to the blacktop for a distance of 1520 meters down to the underground concrete layer of Zurich’s tram tracks.
The work units for the large, spe- cialized excavators consisted of a crew of three and a mobile exca- vator. To avoid damage to the curb stones and adjoining surfaces, one of the construction workers acted as a guide through the narrow cor- ridor of the cramped construction site. The overhead catenary was an obstacle as to how much the boom could be lifted. The space sideways was limited to a few centimetres and adding to this was the general noise and distractions of a large construction site for the operators. This required highest concentrati- on from the driver. Two cameras, one on the right side and one on the rear counterweight could be moni- tored in the cab for added security. A temporary wheeled construction fence pushed along by two const- ruction workers to deflect flying concrete chunks followed the ex- cavators to catch any debris in the vicinity of the rail ripper. A New Holland mobile excavator equip- ped with a concrete ripper head was employed to securely clamp on to the rail as it emerged from the excavator bucket. Most of the
Translation of pages 36 – 39
time, the rail broke to lengths by itself or was broken in to lengths by the rail ripper excavator. Cut- ting torches where needed to cut the newer pieces of rails. After the “yellow gang” from Eberhard had finished, the “white gang” from Iplenia moved in to load the scrap rail. A Neuson mobile digger with a jackhammer attachment was used to remove the last concrete bits still attached to the rail. A busy gang of workers equipped with cutting tor- ches, cut the rails in to manageable lengths for loading and removal. Then the white loaders from Lieb- herr and Caterpillar filled construc- tion waste bin containers that were then trucked away.
Recycled gravel for the base
Eberhard Bau AG used a total of six 30 ton Excavators for the loa- ding of Saturday’s concrete waste and height restrictions forced the operators to use the extended boom position only to load the waste. The concrete rubble dumped in to the 55 marshalled dump trucks made a deafening noise and around 4500 cubic meters of concrete waste where trucked to “BaustoffRecy- lingZenterEbirec” in Ruemlang. With the track and concrete bed re- moved the time had come to engage the “elephant feet”. Like a herd of the same, a couple of 3.5 ton heavy G110 Hydraulic Hammer crushed the lower concrete strata, up to 400 millimetres thick in some places. These hammer where mounted on two Caterpillar 345C Excavators with a weight of 50 tons. Behind the “elephants “a couple of nimble Cat 325C and D excavators remo- ved the crushed, lower strata con- crete and evened out the ground.
As soon as the first meters of earth had been levelled and a membrane installed, the trucks returning from Ebirec dumped the recycled gra- vel layer in. 1200 cubic meters of first class gravel where used to lay the track sub road bed . The Laser control installed in the Caterpillar D6N and D5G LGP bulldozers made it possible to level out the RC-gravel with a tolerance of one centimetre. A Cat 953D LPG was also used in a supporting role. As soon as the Eberhard crew where finishing, the workers from Walo Bertschinger arrived with an ar- mada of their construction ma- chines on the site. They carefully dug trenches in to the new gravel bed to install cables, conduits and shafts. Waiting behind them whe- re heavy transport vehicles with the new pre-fabricated track and switches. Moments after the com- pleted wiring installation, mobile cranes lifted the pre-assembled track sections mounted on small concrete footings into position. Before pouring of the first concrete layer, track installing specialists le- velled and made final adjustments to the new track. It took five hours for the special formulated concrete mixture to cure properly. This was necessary to allow the streetcars to use at least some of the over 2000m of track under construction. It was not until August 16, 2009 that all final work and fine tuning on the new trackwork located at Stadel- hoferplatz, Theater and Gottfried- Keller Strasse was completed.