TEMPORARY WORKS GEOTECHNICAL DESIGN FOR
LARGE SCALE INFRASTRUCTURE PROJECTS
CHRIS BRIDGES
Temporary Works
Can be defined as “any temporary construction
that may be necessary to allow the permanent
works to be carried out”.
Temporary Works
(a) They represent the interface between design and
construction.
(b) They are a key factor in achieving the desired result
safely and with the best cost benefit to the client.
(c) Their design and method solution are often more
challenging than that for the permanent works.
Alternatively, the permanent works design must be
carried out recognising the method of construction that
will be adopted.
Temporary Works - Their Role in Construction - J. R. Illingworth (1987)
Typical Works Undertaken
• Piling platform and crane pad design
• Haul roads
• Excavations and earth-retaining structures
• Rock support design
• Slope appraisals and designs
• Foundations for temporary structures including tower
cranes
Temporary Works - Process
Contractors Contractors Alternatives/ Construction
Objective Preferences Concepts Design Role
Construction
Contractor
Alternatives/Concepts
Design
ContractorsPreferences
Objective
Role
• What
Available
Different
Full-time
Groundwater
are solutions
the
presence
material?
temporary
level available?
required?
works required for?
• Duration
Available
Do
Frequent
Surcharges
nothing?
ofsite
plant?
temporary
visits? works?
• Over-arching
Instrumentation
Preferred / non-preferred
Durability contractual
& monitoring
requirements?
sub-contractor?
• Partial factors / factors of safety
• Construction sequencing
• Interaction with permanent works
Risks
• Time
• Reliance on third party information
• Lack of information
• Consequence of failure
• Cost
Pile & Crane Platforms
Pile & Crane Platforms
CFA rig collapsed across main
London – Paris railway line
(Piling & Foundation Specialists)
Pile & Crane Platforms
Bored piling rig
collapsing sideways due
to soft spot on platform
(Piling & Foundation Specialists)
Pile & Crane Platforms
Port of Brisbane – One fatality
Land reclamation using dredged mud cuttings from
Brisbane River.
Dredged mud overlies by approx. 2m of sand cap
Install wick drain and surcharge for ground improvement to
limit future settlement
•Weight: 80 tonnes
•Track size:
6000mm x 900mm
•equivalent to ~75kPa
Pile & Crane Platforms
• BR 470
Detailed loads for load cases to be
provided by rig contractor/supplier.
Based on Meyerhof – footing
punching through a dense sand layer
over a soft clay.
Examples in BR 470.
Pile & Crane Platforms
Must haves:
• Information on ground conditions (test pits)
• Crane/pile rig loadings etc
• Information on material to form platform
Excavations
• Batters
• Sheet piles
• Cutter soil mixing
• Soil nails
• Rock support – dowels, bolts
• Piles – contiguous, secant, soldier piles, ground anchors
(temporary & permanent)
Excavations – Soil Nails
Excavations – Soil Nails
Shored Mechanically Stabilised Earth (SMSE) Walls
RSS
Soil Nails
Shored Mechanically Stabilised Earth (SMSE) Walls
Excavations – Temporary Ground Anchors
Excavations
Guangxi
“A stitch in time”
Nicholl Highway 2004
What Happened?
Ref.: New Civil Engineer International, May 2005, pp4-7
Conclusions
• Inadequate design and design review
• Poor construction supervision & sequencing
• Ignoring monitoring data
Airport Link Case Studies
• $5bn, 7km Tunnel linking Bowen Hills to the East/West
Arterial Road (Toombul)
• Widening of existing East/West
Arterial
• Reconstruction of the Airport
Roundabout
• Construction of Northern Busway
to Kedron
Kedron
Kedron Brook Cut-
and-cover
Excavation
Kedron Park Hotel
Tunnels
Kedron Brook Cut-and-cover Structure
Contractors Requirements
• Excavation required to 10m below existing
to allow construction of cut-and-cover
roof slab
• Required over a 100m length, through
Kedron Brook to be done in two phases
• Retaining Gympie Road
• Minimum surcharge of 20kPa (contractual requirements)
• Maintain minimum flow through the Kedron Brook (contractual
requirements)
• Material reuse
• Removable system
Kedron Brook Cut-and-cover Structure
Contractors Requirements
Gympie Road
KEDRON BROOK
Phase 2
Phase 1
Kedron Brook Cut-and-cover Structure
Contractors Requirements
Flood Wall built on
Phase 1 Slab
DIVERTED ON TO THE
KEDRON BROOK
PHASE 1 ROOF SLAB
PHASE 2
PHASE 1
KEDRON BROOK
Interface
between Phases
1 and 2
Kedron Brook Cut-and-cover Structure
Contractors Preferences
• Use a system that was readily available with more than
one/two suppliers
Kedron Brook Cut-and-cover Structure
Alternatives / Concepts
• CSM
• Sheet piles - adopted
• Soil nails – partially adopted
• Soldier piles
Kedron Brook Cut-and-cover Structure
Design
• Flood risk (RL5m normal flow to
RL9m flood)
• Analysis undertaken included
design of sheet piles, rock anchors
and walers
• Excavation required below shallow
rockhead
• Rock socket used for temporary
stability until toe anchor installed
• Permits excavation to below toe of
wall. Socket then redundant
• Reused sheet piles, steel walers
for phase 2
Kedron Brook Cut-and-cover Structure
Construction Sequence
Kedron Brook Cut-and-cover Structure
Construction Sequence
Kedron Brook Cut-and-cover Structure
Construction Sequence
Kedron Brook Cut-and-cover Structure
Construction – Phase 1
Kedron Brook Cut-and-cover Structure
Construction – Phase 1
Kedron Brook Cut-and-cover Structure
Construction – Phase 1
Kedron Brook Cut-and-cover Structure
Construction – Phase 1
Kedron Brook Cut-and-cover Structure
Construction – Phase 2
Kedron Brook Cut-and-cover Structure
Construction – Phase 2
Kedron Brook Cut-and-cover Structure
Construction – Phase 2
Kedron Brook Cut-and-cover Structure
Construction – Phase 2
Kedron Brook Cut-and-cover Structure
Construction – Phase 2
Kedron Brook Cut-and-cover Structure
Construction – Phase 2
Kedron Brook Cut-and-cover Structure
March 2010
Kedron Brook Cut-and-cover Structure
March 2010
Kedron Brook Cut-and-cover Structure
August 2010
Kedron Brook Cut-and-cover Structure
October 2011
Kedron Park Hotel Tunnels
Contractors Requirements
• Cut-and-cover tunnel
• Cut required to in excess of Kedron Park
30m depth with final Hotel
structure built within the box
• Church hall within 5m of Open Car
Park
wall, Church within 15m and Moreton Bay
Fig
Hotel within 15m
• Access for construction
Housing
plant at the crest (large Tunnel under
mobile crane loads etc) wall Tunnel
Church and through wall
Hall
• Tunnels (roadheader, drill
and blast) required
underneath the excavation
and through one of the walls
Kedron Park Hotel Tunnels
Contractors Preferences - Alternatives / Concepts
• Initial Design – Stacked tunnel, internal
propping constructed top down. Secant
piles.
• Issues with constructability and cost
• Enquiry from TJH regarding suitability
of soil nails
• Preparation of design for 30m+ high
soil nail wall (24m) / rock cut (6m)
• Revised to 18m soil nail wall and 10m
contiguous piles due to mined tunnel
concerns
Kedron Park Hotel Tunnels
Design – Key Issues
• Tunnelling through walls - constructability
• Settlement of existing structures
• Timescales
• Suitability to gain approval through TJH design review process
(PBA, IV, CNI)
• Appropriate modelling techniques
• Construction plant as crest of wall
• Tower crane
• Existing services
• Protected Trees
Kedron Park Hotel Tunnels
Design – Key Issues 0 5 10 15 20 25 30 35 40 45 50 55 60 65
• Initial feasibility design using simple
35 35
South Wall
Eastern Side
Name: Stiff Clay Unit Weight: 21 kN/m³ Cohesion: 5 kPa Phi: 25 °
30 30
design packages and methodology.
Name: Hard Clay Unit Weight: 21 kN/m³ Cohesion: 5 kPa Phi: 28 °
Name: VLS - LS Siltstone Unit Weight: 22 kN/m³ Cohesion: 22.5 kPa Phi: 30 °
Name: MS Siltstone Unit Weight: 22 kN/m³ Cohesion: 200 kPa Phi: 40 °
1.333
25 25
Proof of concept.
Surcharge (Unit Weight): 32 kN/m³
20 20
Stiff Clay
Elevation (mRL)
• Detailed design incorporating 15 15
excavations through and under. 10
Hard Clay
10
• Nail bond stresses validated using pull- 5
VLS - LS Siltstone
5
out tests during design and construction 0
MS Siltstone
0
phases.
-5 -5
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Distance
Kedron Park Hotel Tunnels
Design - Layout
Kedron Park Hotel Tunnels
Design – South Wall Elevation
Kedron Park Hotel Tunnels
Design – East Wall Elevation
Kedron Park Hotel Tunnels
Design – Section
Kedron Park Hotel Tunnels
Design – Tower Crane
Kedron Park Hotel Tunnels
Design – Construction Sequence
Kedron Park Hotel Tunnels
Design - Instrumentation
Kedron Park Hotel Tunnels
Design – Analysis 0 5 10 15 20 25 30 35 40 45 50 55 60 65
35 35
South Wall
Eastern Side
Name: Stiff Clay Unit Weight: 21 kN/m³ Cohesion: 5 kPa Phi: 25 °
30 30
Name: Hard Clay Unit Weight: 21 kN/m³ Cohesion: 5 kPa Phi: 28 °
Name: VLS - LS Siltstone Unit Weight: 22 kN/m³ Cohesion: 22.5 kPa Phi: 30 °
Name: MS Siltstone Unit Weight: 22 kN/m³ Cohesion: 200 kPa Phi: 40 °
1.333
25 25
Surcharge (Unit Weight): 32 kN/m³
20 20
Stiff Clay
Elevation (mRL)
15 15
Hard Clay
10 10
5 5
VLS - LS Siltstone
0 0
MS Siltstone
-5 -5
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Distance
Kedron Park Hotel Tunnels
Design – Analysis
Kedron Park Hotel Tunnels
Design – Analysis
Kedron Park Hotel Tunnels
Design – Analysis
Kedron Park Hotel Tunnels
Design – Analysis
Kedron Park Hotel Tunnels
Design – Analysis
Kedron Park Hotel Tunnels
Kedron Park Hotel Tunnels
Kedron Park Hotel Tunnels
Construction Role
• Full time
• Record progress during
construction
• Mapping of face to
correlate testing
• Observe testing
• Record groundwater
• Site photography
• ITP sign off
• Site instructions
Kedron Park Hotel
Tunnels
Construction Sequence
Kedron Park Hotel Tunnels
Construction Role
Kedron Park Hotel Tunnels
Construction Role
East Wall
North Wall
Kedron Park Hotel Tunnels
Construction Role
GRP Nails
East Wall
Kedron Park Hotel Tunnels
Construction Role
Western End
Kedron Park Hotel Tunnels
Construction Role
Kedron Park Hotel Tunnels
Construction Role
• Ultimate Load (Pullout)
Test
• Acceptance Testing
• Exhumation of test nails
Kedron Park Hotel Tunnels
Construction Role
Kedron Park Hotel Tunnels
Construction Role
33mm 10mm 22mm
Prediction = 22mm Prediction = 55mm
RS
RS
RS
VLS-LS VLS-LS
Siltstone VLS-LS
Siltstone Siltstone
Mid-South Wall Corner North Wall Mid-North Wall
Lateral Movement vs Wall Height
(Published Results)
0.140
0.120 Bruce and Jewell, 1986
Durgunoglu et al, 2007
Lateral Wall Movement, dh (m)
0.100 Clough & O'Rourke,
1990
Thompson & Miller,
1990
0.080 Stocker & Riedinger,
1990
Ho et al, 1989
0.060 Shen et al, 1981
Bridges, 2012
0.040 Unpublished
dh/H = 0.5%
0.020 dh/H = 0.2%
dh = 4H/1000
0.000 dh = H/1000
0 5 10 15 20 25 30 35
Wall Height, H (m)
Wall Height vs Nail Length
(Published Results)
35
30
Bruce and Jewell, 1986
25
Durgunoglu et al, 2007
Thompson & Miller, 1990
Wall Height (m)
20 Stocker & Riedinger, 1990
Ho et al, 1989
Shen et al, 1981
15 Bridges, 2012
Unpublished
L/H=1.3
10
L/H = 1
L/H=0.5
L/H=0.3
5
0
0 2 4 6 8 10 12 14 16 18 20
Nail Length (m)
Kedron Park Hotel Tunnels
Completed Structure
• Two year design life, 4 month
construction (nail wall).
• 18m deep excavation with further 10m
deep piled wall below
• Over 1500 soil nails 10 to 15m long
(steel and GRP)
• Backfilled with flowable fill
Temporary Works
(a) They represent the interface between design and
construction.
(b) They are a key factor in achieving the desired result
safely and with the best cost benefit to the client.
(c) Their design and method solution are often more
challenging than that for the permanent works.
Alternatively, the permanent works design must be
carried out recognising the method of construction that
will be adopted.
Temporary Works - Their Role in Construction - J. R. Illingworth (1987)
QUESTIONS?
