March/April 2022 - 115

Geotechnical monitoring at Eglinton Crosstown LRT project
Bauer Spezialtiefbau,
was commissioned by
the joint venture U2xU5
to construct approximately
21.7 mi (35,000 m)
of piles with drilling
depths of up to 200 ft
(61 m) for nine shafts and
station structures in the
middle of the city center
of the Austrian capital.
For this purpose, up to
five large rotary drilling
rigs are being mobilized
contract in January. The project involves
the Eglinton Crosstown West Extension,
which extends the Eglinton Crosstown
LRT another 5.6 mi (9 km) farther west
into Mississauga. The Ontario government
and its key delivery partners,
Infrastructure Ontario and Metrolinx,
have awarded a contract with a value of
$729.2 million (€648.3 million) to West
End Connectors to design, build and
finance the project's tunnels. West End
Connectors is a consortium comprised
of Aecon Group, Dragados Canada and
Ghella. The consortium appointed GKM
Consultants to install and commission
state-of-the-art geotechnical instruments
and monitoring systems that
would meet the design needs. The
tunneling contract is the first phase of
the extension. Throughout the project,
GKM and its partnership with GEOInstruments
will progressively deploy
more than 3,000 geospatial and geotechnical
measuring points. GKM-GEO
Monitoring Partners are bridging
instrumentation technologies and complex
monitoring assignments into a
single turnkey solution.
Deepest Piles
Installed in Vienna
As one of the most important infrastructure
measures in Vienna, the
Austrian city's subway network is being
modernized with a new route layout
for the U2 line as well as construction
of a new U5 subway line. Bauer
Spezialtiefbau Ges.m.b.H, the Austrian
subsidiary of DFI Europe member
until fall 2022. For the construction of
the bored piles, the subsequent
construction tasks and expansion work
in most construction sections require
compliance with higher tolerance
requirements compared to the standard.
Requirements include drilling precision
with a maximum tilt deviation of 1%
with respect to the drilling depth from
the drilling surface, and use of a drilling
template that must be constructed
precisely at the approach level down to
+/- 1.2 in (3 cm). For the later use of the
structures, to prevent any interference
currents during subway operation, at
least 10% of the maximum reinforcement
cross section for all reinforcement
cages must be electrically throughconnected
and integrated into the
overall structure. The connections
between the reinforcement bars, which
are overlapped by up to five cage
sections per pile, are carried out by
directly welding the reinforcement bars
using a 1.6 in (4 cm) welding bead during
the installation process on the construction
site. The highlight of the work
is construction of the deepest bored piles
ever executed in Vienna - with
diameters of 46.5 in (1,180 mm) and a
drilling depth of 200 ft (61 m). Due to the
new route layout, an expansion of the
tunnel is required, whereby the piles
take on different functions depending on
their corresponding groups. Based on the
prevailing soil conditions in one partial
section, the deepest piles in Vienna with
a drilling length of 200 ft (61 m) will be
partially cased up to depths of approximately
98.4 ft (30 m), and beyond that
under bentonite support. Given the
ambitious predefined construction
schedule, one 200 ft (61 m) pile per working
day will ideally be constructed on
this section under challenging, very
limited spatial conditions in 2-shift
work using a Bauer BG 45 drilling rig.
Thanks to the use of the digitalization
software " b-project " from BAUER
Spezialtiefbau, all pile construction data
are being collected and processed electronically.
Also, a process-oriented
construction/production system is being
applied, with the aim of guaranteeing
the efficiency of all processes on an
ongoing basis. By the end of 2021, approximately
75% of the commissioned
services were concluded on schedule.
Installation of deepest piles in Vienna
DEEP FOUNDATIONS * MAR/APR 2022 * 115
March/April 2022

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