Zakládání staveb a.s. company finished complete works on protrusion of the underground tube in the Vltava riverbed

After a short pause (October 2001 to March 2002) the Zakládání staveb a.s. company workers returned back to the construction of the Underground IV. C1 - the Vltava River underpass. After the bank cofferdams (dry docks) had been closed and sealed, the casting of the second tunnel tube at the Troja bank was carried out and in March this year exquisite works on the riverbed were started to enable its consecutive protrusion and stabilisation.

Prior to initiation of the trench excavation in the riverbed, pairs of larsens were set in the riverbed to enable binding of vessels, from which the extraction should be carried out. These larsens concurrently played a role of directional and orientation points. It was also necessary to provide the first already mounted tube with steel protection frames, so that they prevented its damage during the excavation with cable grabs. Series of checking measurements were carried out after the trench excavation.

A special measure was used for this measurement, it was gradually moved through the trench and divers simultaneously kept checking the riverbed height. The excavation reacted immediately to the differences measured. At the end of the trench excavation it was possible to carry out dismounting of the spacing frames and at the same time to submerge the bank cofferdam (cofferdams); after the water levels were levelled, the larsens were pulled out from the front sides and thus both bank cofferdams opened to the consecutive mounting of the second tunnel tube.

Text: Ing. Jiří Mühl
Photo: Ing. Libor Štěrba

Picture #1Picture #2Picture #3Picture #4Picture #5Picture #6