Munich:

Underground Railway Line U3-South, Construction Lot 4

Description

The construction lot 4 adjoins construction lot 3, Brudermühlstrasse station, in the north & construction lot 5, Thalkirchen-Obersendling in the south, which was driven by mining means. The lot includes quaternary gravel (upper aquifer), tertiary sands & tertiary darkshale-marl strata. The gravel strata are covered with between 2 m & 9 m of rubble fill in places. The tertiary sands are located next to the lower aquifer, which was cut into at the southern end of the excavation.

The groundwater was lowered by means of open internal & external dewatering. In order to relieve the local residents as far as possible, the Thalkirchen station area was constructed using the cover- & -excavation method with diaphragm walls. In the northern section the excavation was secured by means of overlapping bored diaphragm walls. The part underneath Thalkirchener road was constructed with an excavation which featured partly sloped sheeting walls. The structure at the southern end of the section was constructed inside girder shoring, a sheeting wall & abored wall consisting of vertical & diagonal overlapping elements.

The walls of the excavation were partly stayed back & partly supported by prestressed IPB400 girders. Extensive protection measures such as diagonal overlapping bored walls were required for the under-pinning of adjacent building foundations during the relocation of utilities.