Design and construction of an anchored soldier pile wall for a large underground car park

Felipe Villalobos, P Orostegui

Abstract


The geotechnical conditions of the soil
and the construction conditions of a
retaining wall for an underground twolevel
car park project are described.
The project is located in Concepción’s
downtown, south of Chile. The excavation
support had to prevent any damage for
the Courts of Justice historic building
and surrounding buildings. These are
buildings between four and nine floors
and the Hites building is also classified
as a historical building. Also, any cutoff
of water, sewage, gas and electricity
had to be avoided. The solution adopted
was an anchored soldier pile wall of 8 m
depth around the excavation, where the
soldier piles (H section steel piles) were
driven into semi dense silty sand. Two
lines of anchors were designed vertically
and horizontally separated by 3 m and
3.2 m respectively. The design loads for
the anchors ranged between 300 and
560 kN respectively. The installation and
placement of anchors was studied in
order not to disturb the different stages
of construction. The project included
3596 m2 of anchored soldier pile wall
with 314 post-stressed anchors and
300 soldier piles totalling 3200 m. It is
concluded that the temporary excavation
support solution adopted performed
properly to the high demands set, since
no important deformations were noted
in the building of Courts of Justice, in the
surrounding buildings or in the services of
drinking water, power, gas or electricity.
The city of Concepción was severely
struck by an 8.8 moment magnitude
earthquake on the 27th February 2010.
The construction of the underground car
park was just ready when the earthquake
occurred. No damage was observed in
the car park due to the seismic event.
It is believed that the buried soldier pile
wall reduced the seismic loads acting on
the underground car park structure since
no evidence of damage exists after the
very big earthquake.

Keywords: Anchored soldier pile wall, silty sandy soil, excavation support construction
sequence.


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