34
JANUARY-FEBRUARY 2015
d
&
ri
SITE REPORT
through tohandover of newoperational
platforms and trackswithin a short timeframe
–oftenwith justmonths betweenphased
handovers. Eachhandover then releases the
next stageof demolition and this processwill
continueuntil all trackshavebeendemolished
fromStThomas Street in the south toTooley
Street in thenorth (a total of 16 tracks and
platforms).
Keltbray’s in-house structural engineers,
WentworthHousePartnership (WHP)
produced the temporaryworksdesigns to
enable thedemolition toproceed safely.
Due to thehigh riskprofile associatedwith
thedemolitionworksmanyof thedesigns
were checkedby a thirdparty (Cat 3 check).
Thedemolition and any lifting is rigorously
controlledbyvarious approveddocuments
such asWPP (method statements), permits to
demolish/load and lift.
Thedemolition scopeofworks includes
thephaseddemolitionof the existing station.
Activities included asbestos removal, soft
strip, removal of canopies&platforms,
temporaryworks designbyWHP, installation
of temporaryworks, demolitionof the arch
structures and footbridge, groundworks and
pilingmat installation.
Crucial to the success of theproject is
the safedeliveryof the stagedmilestones to
enable thenext stage toproceed. Byworking
24/7Keltbraywas able tomeet, and inmany
cases better, theprogramme and thereby
help to secure these critical dates. Careful
co-ordination and a collaborative approach
were essential to the successful deliveryof
eachphase. Thereweremultiple complex
demolition interfacesworking in and around
the liveoperational rail station and around
theother activities such as piling, bridgedeck
works, platform and canopy construction,
layingpermanentway,M&Eworks and
commissioning.
In addition, several possessions of the
railwaywere required to enable theworks
tobe carriedout in a safemannerwhilst
minimising the impact on the station and the
surroundingneighbours.
Thedemolitionworks varied from the
heavydemolitionof themain arches thatwere
140m (460 ft) longby40m (132 ft)wide
by7m (23 ft) high to thedemolitionof an
existing reinforced concrete ramp adjacent to
a listed façade. Eachwork areahaddifferent
constraints and thereforedifferent techniques
wereused. The items below cover someof the
works in the first stageof demolition.
Thedemolition todatehas involved the
removal of over 155,000 tonnes of brick,
concrete and fill,with a recycle and re-use rate
of over 99%.
MAINARCHES
Themain archesweredemolishedwith the
latest generationofKomatsuPC360 excavators
mountedwithhydraulichammers. Temporary
workswere installed along the cut line to
ensure the liveplatform just 3m (9.9 ft) to the
north remained stable throughout.
A significant temporaryworks schemewas
required to the east to stabilise the existing
buttresswall. This involved the installation
of tensioned tie rodsup to50mm (2 inches)
indiameter and steelworkprops toprovide
stability to the remaining arches.
STAINER STREET SOUTH
This sectionof structurewas constructed
from concretebeams rather thanbrick arches
due tobombdamageduringWorldWarTwo.
Additionally, the closeproximityof theShard
building and a live fire escape routebelow
provided additional constraints. The solution
was to saw cut along thebeams and then lift
themout using a250 tonnemobile crane.
OLDRAMP
Cut and lift techniqueshad tobeusedon the
OldRamp section to ensure the existing listed
façadewas left undamaged. The existingpiers
wereused as temporaryprops andbyutilising
the strengthof the existing concrete structure,
temporaryworkswerekept to aminimum.
The elementswere liftedout in aweekend
possessiondue to theproximityof the railway
and thepotential collapse radius of the250
tonnemobile crane.
FOOTBRIDGE
Early removal of the footbridgewas required
tominimise theworks in the following stage
therefore thebridgewasdismantledover
the live railwayduringnight lineblocks and
possessions. The structurewas cladwith
scaffold to facilitate theworks.Oncede-clad
themain structuralmemberswere liftedout in
apossessionwith a250 tonnemobile crane.
With somany sensitiveneighbours
environmental issueswereof utmost
importance and therefore themanagement of
noise, dust andvibrationwere critical to the
continuedprogress and success of theproject.
Noisemonitoringwas set up around the site to
monitor against levels set out in theSection61
Agreement as agreedwith the local EHO. This
is a formal agreementwith the local authority
that sets out theparameters and limits for
noise, dust, vibration andworkinghours for
theproject.
Best PracticableMeans (BPM) isused at
all times tominimisenoise generationon
site.Noise screens andother localisednoise
reductionmethodswere employed tohelp
reduce the levels. For example, pulverisers
wereused rather thanbreaker attachments,
switchingoff engineswhenplant isnot in
use. Local businesses,GuysHospital and
residents arekept informedbyCostainof any
works thatmay result indisruption. Start of
shift briefings includemeasures tobe taken
tominimisenoisewhenworking around the
hospital, businesses and residents.Vibration
monitoringwas installed inGuysHospital to
monitor critical equipment in this building.
No triggerswere reached andno complaints
were receivedduringKeltbray'sworks.
Demolitionofmassivebrick structures
in a city environment has thepotential to
releasedust therefore several dust suppression
unitswereused to control this aspect of the
works. Thesewas set up along the lengthof
thedemolitionworking face anddirected to
the appropriatedemolition activity to ensure
dust releasewasminimised.Dustmonitoring
is carriedout on site and around the site
perimeter byCostain. Pollutionprevention
was furthermanagedby ensuringmaterials
andwastedidnot enter anydrainage system,
fuelwas stored away fromdrains indrip trays
protected fromvehicular traffic inbunded
fuel bowsers located in a secureCOSHH
area and refuelling,wherepracticable,was
carriedout at adesignatedpoint equipped
withdrip trays and spill kits, and ensuring
that operatives are trained in theuseof spill
kits andprocedures for removal of fuel/oil
contaminatedmaterial.
■
A tension tie rod schemewas
designed byWentworthHouse
Partnership
Work could not be allowed
to interferewith the smooth
operation of the station
