Download iU-21-24-902 Soilfrac compensation grouting to mitigate damage due to tunnelling Perth NMR City Project

ENGINEERS AUSTRALIA
ENGINEERING
EXCELLENCE AWARDS
Level 2 Joint Entry of:
Perth New MetroRail City Project –
Soilfrac Compensation Grouting to
mitigate settlement induced damage
to buildings due to tunnelling
For the Category of:
Project Awards: Small Business Ventures/Projects & Reports
Entered by:
Keller Ground Engineering Pty Ltd
Leighton Kumagai Joint Venture Pty Ltd
GROUND ENGINEERING
Principle Entrant:
Keller Ground Engineering Pty Ltd
Level 1, 4 Burbank Place
Baulkham Hills NSW 2153
Joint Entrant:
Leighton Kumagai Joint Venture
1 Altona Street
West Perth WA 6005
Contact: Oliver Batchelor
Tel: 02 8866 1155
Email: [email protected]
Contact: Matt Williams
Tel: 08 9324 1166
Email: [email protected]
CONTENTS
Soilfrac Compensation Grouting enabled two 6.9m
diameter tunnels to be drilled less than 6m below the
shops, offices and restaurants of central Perth without the
general public being aware of the works”
GROUND ENGINEERING
Executive Summary
page 1
Description of Entry
page 2
Control Systems & Review
page 15
Resources
page 20
Referees & Project DVD
page 25
EXECUTIVE
SUMMARY
Soilfrac Compensation Grouting was used to allow the driving
of tunnels without impacting on services and structures above
the line of new MetroRail tunnels in Perth CBD. The design and
implementation of the system was executed by close co-operation
of Keller’s engineers in Sydney supporting LKJV onsite in Perth.
The project demonstrated excellence by:
Performance - ensuring structures were unaffected by
• tunnelling.
Community Focused - Ensuring no disruption to the local
• community
and continuous unhindered use of properties in a
complex and congested urban environment.
Innovation – the technique combined traditional grouting
• techniques
with sophisticated monitoring and control.
Communication - achieving the project requirements through
• close
co-ordination and communication between numerous
stake holders and participants.
GROUND ENGINEERING
Safe - the work was completed with an unblemished safety
• record
due to the development of numerous new safe working
practices to take account of the new methods and techniques
being performed.
page DESCRIPTION OF ENTRY
BACKGROUND
The Public Transport Authority (PTA) of Western Australia awarded the $330m tender for the
design, construction and maintenance of the New MetroRail City project to the Leighton
Kumagai Joint Venture (LKJV), a joint venture between Leighton Contractors and Kumagai
Gumi of Japan.
Left: Ground Displacements
due to tunnelling
Above Right: Aerial
photograph of the
Gold Group Buildings
GROUND ENGINEERING
The project involved the construction of 1.5km of underground
rail lines and two new stations and presented a wide range of
engineering challenges. A prime challenge was to ensure that the
tenants trading in the city were not inconvenienced or buildings
were not damaged by the boring of two 744m long, 6.9m diameter
tunnels through the water bearing sandy soils beneath Perth’s city
centre. The contract was administered by New MetroRail, a projectspecific office established by the PTA.
The tunnel alignment was primarily below roads and rail reserves,
however in order to link in with a new underground station the
tunnels passed below four buildings whose foundations were
only 6m above the tunnel crown. The four buildings on William
Street, identified as the “Gold Group” due to their importance
to the project, presented significant challenges in identifying a
protection measure that could be implemented without disrupting
the occupier’s business, pedestrian access or road traffic flow and
ensuring the integrity of the buildings and services.
page DESCRIPTION OF ENTRY
BACKGROUND CONTINUED
The Gold Group Buildings, occupied by shops, offices and fast food outlets, covered an
area of approximately 2000m2 and consisted of four structures varying between two and
six storeys, some with basements and a combination of concrete raft, concrete strip and
brick foundations.
The maximum magnitude of settlement due to tunnelling operation
was predicted to be of the order of 20mm, this, combined with
the varied foundation systems, the tunnel skew and the partial
undermining of the buildings presented the greatest risk of damage
due to differential movements and their likely impact on the
buildings and the trading activities therein.
The soil conditions below the buildings consisted of loose to medium
dense Sand with the groundwater level only 3.0m below ground
level. This meant that the full magnitude of settlement from the
tunnelling operation would occur within hours of the tunnelling
advancing below the building.
LKJV engaged Keller Ground Engineering (KGE) for the design,
installation and operation of a Soilfrac Compensation Grouting
System for the protection of the Gold Group buildings with the
following other organisations in supporting roles.:
Ryan & Hill – undertaking building condition surveys and
• Airey
protection assessments
– Preparation of LKJV’s Ground Settlement, Building
• Geoconsult
Protection and Repair Plan
Spatial Solutions – Instrumentation installation and
• Fugro
monitoring system and personnel, with supply of instrumentation
by ITM soils and Slope Indicator.
Requirements
The requirements of the works were to ensure that the buildings were maintained in
continuous unhindered operation with no significant damage resulting from the
tunnelling works.
In addition the protection works should have minimal disruption possible to the roads,
buses, pedestrians, and building tenants as well as the daily life of Perth’s residents. Initial
discussions between Keller Ground Engineering and Leighton Kumagai JV (LKJV) were
page DESCRIPTION OF ENTRY
BACKGROUND CONTINUED
focused on conventional techniques to support the buildings (as summarised in Table 1)
each method presented their own specific challenges however the common problem
was one of access and minimising disruption. Keller subsequently proposed the use of
Soilfrac Compensation Grouting (Soilfrac).
The benefits of the system soon became apparent, the principle benefit was that it allowed
the protection works to take place from a one central location without the requirement to
access the properties and in any way impact on its users.
In addition Soilfrac Compensation Grouting provided a flexible approach to protection by
controlling the settlement on a real time basis as opposed to installing structural support or
mass ground treatment that would have been designed and installed for the worst case
settlement/damage profile.
Table 1: Possible methods for Gold Group building protection
Method
Technical Confidence
Access
Stakeholder Disruption
Overall LKJV/Program Impact
Underpinning, e.g. piles etc
Low (need to review structures)
Difficult (basements occupied,
major bus route outside)
Significant (Need to move
tenants out of basements)
None (but negotiation required
with building owners)
Grout block to prevent soil
movement installed from
ground or basement
High
Difficult (basements occupied,
major bus route outside)
Significant (Need to move
tenants out of basements)
None (but negotiation required
with building owners)
Grout block to prevent soil
movement from TBM
High
Possible
None
Significant
Propping
Low (damage may still occur)
Difficult
High
None (but negotiation required
with building owners)
Reinforce the building structure
Low (damage may still occur)
Difficult
High
None (but negotiation required
with building owners)
Ground Improvement
Structural protection
Compensation (during or after settlement)
GROUND ENGINEERING
Grouting from
tunnel
Low
Good
Minimal
Slight
Compensation Grouting
High
Reasonable
Minimal
None (if access shaft can be
negotiated)
page DESCRIPTION OF ENTRY
BACKGROUND CONTINUED
To undertake the protection of the Gold Group by Soilfrac Compensation grouting required
creating a shaft in the middle two lanes of William Street and have regular monitoring
surveys undertaken on the buildings and footpaths around. Hence, the following stake
holders needed to be liaised with on a continuous basis:
• PTA and LKJV management
• LKJV tunnelling operations to determine progress
• City of Perth about permitting and minimising disruption
• Transperth for the bus scheduling
• Owner’s representatives for the four Gold Group buildings
• All of the tenants of the Gold Group buildings
The general public (accessing the buildings, walking along
• William
Street), and
• The general public road traffic that used William Street.
Leighton Kumagai gained confidence in the Soilfrac Compensation
Grouting technique through demonstration of Keller’s experience
in the method overseas and in the capability of their locally based
engineers.
This confidence allowed them to jointly promote the method to the
PTA and the project stake holders through a series of presentations
and complimentary reports.
GROUND ENGINEERING
page DESCRIPTION OF ENTRY
SOILFRAC COMPENSATION GROUTING THEORY
Soilfrac Compensation Grouting involves the injection of grout into the ground between a
structure and the tunnel during tunnelling. Whilst the implications of high pressure grouting
have been known since the early 20th century they have more often been regarded as
a limitation of the grouting technique, associated with uncontrolled heave with related
damages to services, structures and pavements.
They were only grouped and applied to the challenge of settlement
mitigation for tunnelling in the late 1980’s. A large-scale trial of the
technique was performed in London Clay in advance of London’s
massive Jubilee Line Extension project in 1992. The success of the
trial lead to its adoption on large sections of that project to protect
buildings and structures overlying the proposed excavations and
subsequent acceptance of the method in cohesive soils.
Soilfrac is a development of conventional permeation grouting
which utilises the normally undesired effect of hydro-fracture to
form a compensatory lens of grout in the soil thereby balancing the
ground loss due to tunnelling and maintaining the overall soil balance
between the tunnel and the ground surface.
GROUND ENGINEERING
Above Middle: Schematic
showing grout fractures from a
TAMP pipe
Above Right: Insitu grout
fractures emanating from a
TAM pipe in clay
The mechanism of hydro-fracture and subsequent ground movement
have been described in some detail by a number of authors
including Linney & Essler (1992) and Essler, (1998), a brief summary of
this mechanism follows. In cohesive soils, conventional permeation
grouting is not possible due to the soil pores being too small for
cement particles to enter the flow paths between the soil particles.
page DESCRIPTION OF ENTRY
SOILFRAC COMPENSATION GROUTING THEORY
If the grout is pumped at sufficient pressure, the overburden pressure
is exceeded parting the soil and a fracture of grout forms in the soil
matrix. Repeated grout fracturing results in initial consolidation of
the soil followed by ground heave. This initial phase of repeated
injections to consolidate the soil is termed ‘conditioning’.
Soilfrac Compensation Grouting has been performed in cohesive
soils with some regularity on major European tunnelling projects
in the last 15 years. The use of the technique in the granular soils,
as found below the Perth CBD, has been carried out much less
frequently with only two documented examples. Injection of a
cement suspension grout into granular deposits will not form a hydrofracture until the soil pores have been ‘choked’ or filled and the soil
pre-grouted with a grout that is of sufficiently low strength to ensure
hydro-fracture grouting can subsequently take place. It is against
this background that the Soilfrac technique was promoted, adopted
and implemented in Perth.
In order to facilitate the repeated injections of grout below isolated
sections of a structure the Soilfrac method uses a special grout
injection tube called a ‘Tube-a-Manchette’ or TAM pipe.
The TAM pipe consists of a steel or plastic pipe with injection holes
or ports drilled at approximate 0.5m centres. The injection holes are
covered with a rubber sleeve which acts as a simple non return
valve. A double packer is inserted down the pipe and the packer
rubbers inflated either side of the injection port to allow an isolated
injection of grout.
The pressure of the grout inside the TAM expands the rubber sleeve
and allows grout to flow into the soil at the required location, when
the pump pressure ceases the rubber sleeve contracts and prevents
grout flowing back into the pipe. The system allows repeated
injections of grout in precise locations.
GROUND ENGINEERING
The hydro-fracture grouting is carried out in a pre-determined zone
of ground between the tunnel and the ground surface. The location
of the hydro-fracture zone is determine by considerations such as the
overburden pressure, the proximity to the tunnel and potential for
grout flow into the TBM and the geology.
page DESCRIPTION OF ENTRY
SOILFRAC COMPENSATION GROUTING DESIGN
Design
The central feature of Soilfrac is that it is a bespoke method, designed and implemented
on a project specific basis. The design and operation is as much affected by the buildings
to be protected, the tunnelling operation and the access limitations as by the geology and
settlement characteristics of the soils and the soil structure interaction with the structures
and services above.
Accordingly the design of the system for the Perth MetroRail was
developed in close co-operation and consultation between
Keller’s Sydney based engineers and LKJV’s site staff over a period
of approximately eight months prior to commencement of any
activities on site.
A number of differing access scenario’s were investigated and
designed with options of subterranean access from basements in
neighbouring buildings considered, as well as shallow excavations in
William Street.
The final access opted for was a shaft excavated within William
Street that only required the closure of one lane and enabled all
operations to be carried out remote from and without interference
to the activities of residents and users of the protected structures.
Steel TAM pipe with rubber sleeve
Packer inside a cut away TAM pipe
GROUND ENGINEERING
Double Pneumatic Packer
page DESCRIPTION OF ENTRY
SOILFRAC COMPENSATION GROUTING DESIGN
Once the working area is established, the principle factors to consider in design are the
magnitude of settlement expected and the rate at which the settlement will occur.
The greater the magnitude of settlement the closer the frequency
of TAM pipes required. High rates of settlement require greater rate
of injections (no. of sleeves injected per hour) and hence a greater
requirement for grouting and monitoring resources.
The design of the system was carried out by Keller’s engineers
based on their personal experience overseas aligned with that of
Keller worldwide. A peer review procedure was adopted with an
independent expert in the field, with Mr. Robert Essler, one of the
pioneers of the system providing this review from the UK.
Above Left: Final position of
Access Shaft in William Street
GROUND ENGINEERING
Above Right: One of the
considerations for installation
of TAM pipes
The final design comprised the installation of 57 No. TAM pipes,
each approximately 40m to 50m long. The frequency of the TAM
pipe sleeves was approximately 1 sleeve per metre squared with
a redundancy/precaution of 100% built into the system should
unexpectedly large settlement occurs in an isolated location or if
sleeves should become blocked following repeated use.
page DESCRIPTION OF ENTRY
SOILFRAC COMPENSATION GROUTING INSTALLATION
Installation
The TAM’s were installed by means of a cased drilling system requiring accurate drilling to
lengths of up to 50 metres. A duplex drilling method was considered the most appropriate
for providing the necessary accuracy on the final TAM location and preventing structural
movement due to ground loss during the installation.
A purpose built drill mast was fitted to a turntable which in turn was
bolted to the concrete base of the shaft to provide a stable drilling
platform.
When the drill mast was orientated to the correct azimuth for a
drill position, hydraulic jacks would lock the mast against the wall
of the shaft at the back and front of the mast itself to maintain its
orientation during the entire drilling and installation procedure.
Bentonite slurry was used as the flushing medium which also acted
as a natural lubricant to prevent frictional resistance as the drilled
casings were advanced below the buildings.
The Bentonite was recycled within the site set-up area after
separation of the drilling cuttings. This system minimised the volume
of drilling spoil that had to be removed from site. The duplex drilling
system consisted of an outer casing of 114mm diameter and a
76mm diameter inner rod.
Left: Plan indicating TAM
arrangement below
buildings together with work
compound in William Street
and tunnel alignment.
page 10
DESCRIPTION OF ENTRY
SOILFRAC COMPENSATION GROUTING INSTALLATION
During the initial installations the TAM’s were surveyed using a GIRO
borehole survey tool. The survey tool had an accuracy of +/-50mm
in 50m which allowed the final TAM locations to be plotted in plan
and elevation to acceptable limits.
In the initial surveys of the TAM installations two TAM pipes were found
to have deviated unacceptably close to the proposed tunnel bore
and it was concluded that every borehole would be surveyed prior
to the TAM installation.
The drilling equipment was mobilised to site at the beginning of July
2005 and drilling works were completed in early October 2005. In
total 57 No. TAM pipes were installed with a total length of 2,400m.
Above Left: Works
Compound in William Street
GROUND ENGINEERING
Above: Installation of the
TAM pipe in drilled hole.
Note the red caps covering
previously installed TAMs.
page 11
DESCRIPTION OF ENTRY
SOILFRAC COMPENSATION GROUTING CONDITIONING
Grouting
The grouting works were carried out in two phases. Firstly the conditioning phase, in
which the soil in the Soilfrac zone is progressively grouted and fractured to a point where
movement is observed at surface, followed by the Active phase where the grout is
injected in response to structural movement observed by the monitoring systems to
control building movements to within specified limits during the advance of the tunnels
under the building.
Conditioning grouting phase
The condition phase was carried in a number of passes. The initial
passes were carried out over the whole of the TAM array as a general
“background tightening” operation. Subsequent grouting passes were
targeted at areas beneath the structures within the zone of influence
from the predicted settlements from the building risk assessment. There
were 3,042 sleeves available to the grout engineer which could be used
to inject grout and control soil/structural behaviour.
GROUND ENGINEERING
Above: Placing the packer
and grout injection from
within the shaft
During the conditioning phase an average uplift across the building
of 3mm was targeted. Using information and experience of similar
projects in Europe the injection treatment was planned on theoretical
injection volumes. Volumes and pressures were then adjusted in
response to the soil/structural behaviour observed through the
monitoring system.
page 12
DESCRIPTION OF ENTRY
SOILFRAC COMPENSATION GROUTING CONDITIONING
The grout used consisted of a cement/bentonite blended grout.
The grout was mixed in a high shear colloidal mixer to ensure that a
stable grout was mixed. Standard QA controls comprising tests for
specific gravity, flow, bleed and strength were carried out on the
grout during the injections.
Prior to commencing the conditioning phase a small scale
verification procedure was performed to demonstrate that the
system was working adequately. The procedure involved a series of
injections to carry out a controlled heave of part of the structure.
The tunnel lining designer’s questioned the potential risk of excessive
pressure on the tunnel lining from the active phase grouting
operations carried out concurrent with the tunnel construction.
Pressure dissipation trials were carried out on a number of sleeves
and TAM pipes during the initial phase to assess the time lag for
pressure stabilisation in the system on completion of a grout injection
pass.
The pressure was recorded in real-time using the grouting computer
with the pressure found to drop to below 50% within two to three
seconds then tail off fully after approximately 30 seconds. Although
the pressure dissipation trials revealed no long term excessive
pressure it was considered prudent to introduce a grouting exclusion
zone around the TBM.
This exclusion zone would provide safeguard against the potential
risk of excessive pressure on the lining and possible grout migration
from the active phase grouting zone into the head of the TBM. An
injection pressure limit was also put in place with all sleeves within
two metres of the TBM path and constructed tunnel lining.
The placement of an exclusion zone around the head of the TBM
meant that it would be impossible to grout in the desired location
until the TBM progressed past this point, as such the methodology
was amended to allow for a controlled pre-heave of the structures
by approximately 3mm which would act as a buffer until the
compensation grouting could commence upon TBM advancement.
GROUND ENGINEERING
Above: Verification results
indicating controlled heave
by rejected injection
During the grout injections for each grout pass the grouting engineer
reviewed the real-time monitoring data of the building to gauge
page 13
DESCRIPTION OF ENTRY
ACTIVE SOILFRAC COMPENSATION GROUTING
the reaction of the building to the injection. The initial uplift of
the structure was generally followed by a small relaxation of the
movement. Both the initial and second pass had similar volumes of
grout injected. The initial movement was approximately 1.3mm with
the second pass provided approximately 1.6mm. A third pass was
carried out with half the volume of grout.
The key observation from this pass is that no relaxation took place
within the structure on completion of the grouting. This indicated
that any subsequent grouting would induce uplift within the
structure. Figure X shows a contour plot of the variability of grout
volume injected to achieve the final conditioning.
Active grouting phase
The first tunnelling drive below the buildings commenced in January 2006, the second
drive taking place in August 2006 each drive taking approximately two weeks to
complete.
During the tunnelling period the grouting operations, consisting
of observation of movement and subsequent grout injection to
compensate for the settlement, were carried out on a continuous
round the clock basis by Keller’s core team of engineering staff who
temporarily re-located from Sydney. Between the tunnel drives the
shaft in William Street was capped and normal traffic movement was
maintained.
The outcomes of Active grouting phase are described in detail in the
section of this report entitled Control Systems & Reviews.
References
L.L. LINNEY AND R.D. ESSLER: ‘Compensation Grouting Trial Works at Redcross Way, London’,
Grouting in the Ground Conference ICE, 1992.
R.D.ESSLER: ‘Control of settlement by Compensation Grouting, Jubilee Line in London’, Big
Digs around the world 1998, ASCE National Convention, Boston, ASCE Geotechnical Special
Publication No. 86.
GROUND ENGINEERING
Above: Relief plot showing
grouting intensity in
conditioning phase
page 14
CONTROL SYSTEMS & REVIEWS
Risk
Category
Description of
Degree of Damage
Description of Typical Damage and Likely Forms of Repair
1
Very slight
Fine cracks easily treated during normal redecoration.
Damage generally restricted to internal wall finishes Perhaps
isolated slight fracture in building. Cracks in exterior brickwork
visible upon close inspection.
0.1 to 1
0.05 to 0.075
2
Slight
Cracks easily filled. Redecoration probably required.
Recurrent cracks can be masked by suitable linings. Exterior
cracks visible: some re-pointing may be required for weathertightness. Doors and windows may stick slightly.
1 to 5
0.075 to 0.15
3
Moderate
Cracks may require cutting out and patching. Tuck pointing
and possibly replacement of a small amount of exterior
brickwork may be required. Doors and windows sticking.
Services may be interrupted. Weather tightness often
impaired.
5 to 15 or a
number of
cracks greater
than 3
0.15 to 0.3
Above: “Building Damage
Classification” (from Burland
et al., 1977 and Boscardin
and Cording, 1989)
Approx Crack
width (mm)
Max Tensile
Strain (%)
Specification & Objectives
The performance requirement of the protection system was to
maintain the incremental damage to within the “slight” damage
classification as described in the criteria established from Burland
et al., 1977 and Boscardin and Cording, 1989 and as summarised
above.
This was interpreted to achieve the following goals:
• Limit settlement of an individual footing to 10mm
• Limit differential settlement across the building to 1 in 500, and
• Limit the heave to less than 5mm.
page 15
CONTROL SYSTEMS & REVIEWS
MONITORING & REVIEW
Monitoring Review
Soilfrac Compensation Grouting is an observational method which uses the observed
results of the previous actions to determine the next action, as such the instrumentation
and monitoring is a critical component. A combination of instrumentation devices was
used to provide a complete picture of the buildings’ movements. These were:
prisms read from robotic theodolites on the building
• Optical
facades every hour
electro-levels spanning inside the buildings along
• Wireless
columns and transverse to the tunnels measured at two minute
•
•
intervals;
Building settlement points (pins and retro/photogrammetry
targets).
Surface settlement points.
In addition to the instrumentation placed on the Gold Group
buildings, two deep settlement arrays were installed within 50
metres of the first building to accurately determine the size and
characteristics of the tunnel settlement trough. The array consisted
of combinations of:
settlement points which were reinforcing bars drilled and
• Deep
grouted 1m below the ground;
• Rod extensometers;
inclinometers fed back wirelessly into the monitoring
• In-place
system; and
• Other surface and building settlement points.
To coordinate the compensation grouting, a specific Building
Protection team was created with key personnel from the
monitoring, tunnelling and compensation grouting operations
together with overall management coordination. The conditioning
phases provided the team with information on pressures and
volumes during each grout injection.
GROUND ENGINEERING
Robotic theodolite layout
and visibility of building
facades from each
Two dedicated teams of surveyors ran a swing shift to provide
twice daily manual readings at around 12 hour intervals. These
manual surveys provided verification and a baseline for the wireless
electronic monitoring devices.
page 16
CONTROL SYSTEMS & REVIEWS
REVIEW
Review
Above: Flow Chart of
Information and Planning
Meetings for Soilfrac
Compensation Grouting
In order to ensure that the active grouting could be correctly implemented the grouting
engineering personnel were given access to the real-time monitoring and structural
monitoring systems operated by LKJV.
In addition continuous updates of the TBM’s location were provided
by the TBM driver who notified the Keller Grouting engineer as they
were pushing and building each individual tunnel ring. Keller plotted
the movement of the TBM complete with the TBM exclusion zones in
order to facilitate the grouting operations.
page 17
CONTROL SYSTEMS & REVIEWS
CONTINUED
A meeting between key management personnel from the TBM,
monitoring and grouting operations was held twice daily to provide
updates of the TBM progress, monitoring data and grouting analysis
for the previous 12 hours. These meetings also allowed review of the
next 12 hours work including any additional monitoring requirements
and proposed grouting plan. The information from the monitoring
and TBM allowed KGE to tailor the grouting program based on the
observed movements.
Outcome & Results
The conditioning phase raised the structures by approximately 3mm and maintained
the angle of distortion well within acceptable limits. As the TBM approached the Gold
Group buildings the actual settlement being observed was much less than the system was
designed to handle.
This information was converted to a volume loss from tunnelling
and in conjunction with the grout efficiency determined from
the conditioning phase allowed a lower intensity of grouting to
be planned for the active phase. The active grouting plan was
reassessed on an ongoing basis in response to the observed
movement of the buildings.
The active phase of the compensation grouting operation started
when the TBM face was within the influencing distance to the first
encounter structure. To achieve the aim of the active phase of
keeping the structure within acceptable limits, only a small amount
of grouting was carried out.
The settlement plot (left) details in real-time the movement of the
structure and the corresponding grouting carried at the time as the
TBM passed through an area. The grouting program was designed to
limit the settlement to back to normal background structural levels
not keep the structure at the post conditioning elevation. The active
phase was carried out for both running tunnels.
GROUND ENGINEERING
Above: Anticipated
settlement without Soilfrac
and Actual Settlements
achieved.
page 18
CONTROL SYSTEMS & REVIEWS
CONTINUED
Conclusion
This application of Soilfrac and the combination of instrumentation was a unique and
innovative solution to the protection of the Gold Group buildings.
Such an operation could have only been
achieved with the close consultation of
all parties involved within an “integrated”
environment, rather than a simple
subcontract for construction services.
Despite the constraints of the site,
compensation grouting with the high
level of monitoring yielded a highly
successful result.
For the successful implementation of this
compensation grouting system, there
were at least 30 people involved from a
number of organizations in the design,
instrumentation, construction of the shaft
and TAM arrays, grouting operations, 24
hour site supervision, monitoring surveys,
plus engineering and management
reviews.
Right: showing profile of
grout volume injected as the
TBM progressed in the active
phase
GROUND ENGINEERING
Their combined commitment
to maintaining open lines of
communication produced the results
described here.
Soilfrac Compensation Grouting enabled two 6.9m
diameter tunnels to be drilled less than 6m below the
shops, offices and restaurants of central Perth without
the general public being aware of the works”
page 19
RESOURCES
Organisation
The various organisations who worked together to make the project
the success it was include:
• Public Transport Authority (PTA) - owner
• Leighton Kumagai JV – principal contractor
Ground Engineering (KGE) – Design, installation and
• Keller
operation of a compensation grouting system
Spatial Solutions – Instrumentation installation and
• Fugro
monitoring system and personnel
• ITM-Soils – Supply of wireless electrolevel beams
• Slope Indicator – Supply of subsurface instrumentation
Ryan & Hill – Undertaking building condition surveys and
• Airey
protection assessments
• Geoconsult – Preparation of LKJV’s Ground Settlement, Building
Protection Plan
– Lead design consultant for tunnels and below ground
• Maunsell
structures
– sub consultant to LKJV for geotechnical,
• Geoconsult
dewatering, temporary works design, and building protection
design
• SKM/SMEC – Design verifiers
GROUND ENGINEERING
page 20
RESOURCES
CONTINUED
People
The following people were the key or lead people involved in the
compensation grouting works:
Matt Williams (Special Contracts Manager, LKJV) – Related role
included overseeing all building protection and monitoring works,
including the establishment of the initial contract with Keller
and subsequently with Fugro, ARH, ITM and Slope. Ran the daily
compensation grouting management review meetings.
Oliver Batchelor (Concept Development, KGE) – Proposal and
development of the conceptual solution, including promotion of the
Soilfrac concept to LKJV and PTA.
Chris Nobes (Technical Specialist, KGE) – Development of the
conceptual plan to detailed design stage and implementation
thereof based on specialist knowledge and previous experience
of compensation grouting. Responsible for the performance of the
compensation grouting works in compliance with specification.
Simply put, the person who would have shouldered the responsibility
had it not complied.
Jon Stretch (Operations Manager, KGE) – programming of the
inter-related aspects of the installation and grouting works and
implementation of safe works practices.
Peter McGough (Senior Geotechnical Engineer, LKJV) – Overseeing
of all instrumentation and monitoring systems on the project,
including design, managing monitoring, reviewing and interpretation
of all monitoring data collected (versus design predictions).
GROUND ENGINEERING
Ritchie Mulholland (Chief Monitoring Surveyor, Fugro Spatial
Solutions) – Responsible for installing and ongoing operation of all
instrumentation and monitoring systems on the project, including
scheduling the personnel for manual surveys and ensuring
consistency and timeliness of the results.
page 21
RESOURCES
CONTINUED
Henry Yamazaki (Tunnelling Manager, LKJV) – Responsible for
tunnelling operations, including providing feedback.on operational
status, and making modifications as shown by the monitoring
interpretation.
Eric Hudson Smith (Geotechnical Manager, PTA) – Oversaw all
geotechnical, environmental, building protection and monitoring
matters on behalf of the owner.
Another 20 people were involved in the design, instrumentation
installation, construction of the shaft and TAM arrays, grouting
operations, 24 hour site supervision, monitoring surveys, plus
engineering and management reviews.
GROUND ENGINEERING
page 22
RESOURCES
PLANT AND EQUIPMENT
The installation and implementation of the Soilfrac Compensation Grouting system
required various items of specialist plant and equipment that were not available in
Australia nor available as an ‘off the shelf” product overseas. In addition, given the limited
time scale from instruction to carrying out the works, significant items of specialist plant
had to be procured, assembled and commissioned as part of the overall project process.
Drilling
With limited space available for a working compound in William
Street and the restricted shaft diameter a specialist drilling mast was
custom built in Italy to Keller’s specifications. The mast was fitted
with a rotary-duplex head and powered by a specially modified
remote hydraulic power unit necessitated by the site restrictions and
the need to maintain clean air conditions in the bottom of the shaft
during operations.
A rotary duplex drilling system was utilised to maintain directional
stability in the variable soils with the added advantage of minimal
over break to avoid settlement.
Grouting
A key requirement of the grouting process is that each grout injection is individually
controlled to ensure that fracture occurs and that design pressure and volume limits are
not exceeded which otherwise might have the potential to cause uncontrolled movement.
All grouting records are electronically collated for monitoring and interpretation by the
grouting engineer to enable the appropriate grout parameters for future grout injections.
In order to control and record the number of injections required on a
grouting project of this scale it is necessary to use a micro-processor
controlled and recorded grouting unit. With this equipment not
available as a standard unit Keller custom built a grout pumping
station containing 4 No. electric/hydraulic single ram double
oscillating pumps capable of delivering flow-rates between one and
501/min of pressure up to 10Mpa.
GROUND ENGINEERING
Above: Specially
constructed drill rig for
horizontal duplex drilling
The mixer, pumps and micro-processor were sourced in Europe and
the unit was assembled by Keller in the UK under the direction of
the project specialist, Chris Nobes who visited the UK to direct his
requirements for the unit.
page 23
RESOURCES
PLANT AND EQUIPMENT CONTINUED
In operation the grout was mixed by colloidal mixer, then transferred
to an agitating tank contained within the purpose built grouting
container.
The safety pressure limit for this project was set at 2MPa. Each pump
was controlled by computer on which limits could be preset for
maximum pressure, grout injection flow-rate and volume injected.
These limits were set for each sleeve of each TAM within a database.
The database could be accessed at any time and the values
adjusted by the grouting engineer if required. The operator of the
computer control system was able to view pressure and flow-rate
graphs in real-time during any single or multiple injections on the
computer screen.
Above Left: Pump unit and
grout storage tank
GROUND ENGINEERING
Above Right: Cinaut
computer for grouting
control and recording
Left: 3D schematic view of
the grout pumping station
page 24
REFEREES
It is not possible to provide formal referees as the overall project
is still in contract. However the following representatives would be
pleased to answer any questions relating to the works.
Rob Wallwork (Project Director, LKJV) – 08 9424 5500, 0411 259 451
Richard Mann (Project Director, PTA) – 08 9326 2410, 0419 964 209
In addition the project has been described in a technical paper
“Soilfrac Compensation Grouting for Building Protection on the
New MetroRail City Project” by Matt Williams and Chris Nobes
and will be presented in Perth at a special seminar organised by
Engineers Australia, Australian Tunnelling Society and the Australian
Geomechanics Society on 12th September 2007.
Above: The ABC covered the
Soilfrac works on the evening
news (see DVD)
GROUND ENGINEERING
page 25
Soilfrac Compensation Grouting enabled two 6.9m
diameter tunnels to be drilled less than 6m below the
shops, offices and restaurants of central Perth without
the general public being aware of the works”