P. McGough. Geotechnical Instrumentation and Monitoring for the New MetroRail City Project, Perth, Western Australia

1. Geotechnical Instrumentation and Monitoring for the New
MetroRail City Project, Perth, Western Australia
P.G. McGough
Instrumentation and Monitoring Manager, Leighton Kumagai Joint Venture, Perth
M. Williams
Special Contracts Manager, Leighton Kumagai Joint Venture, Perth
ABSTRACT: The New MetroRail Project involved a significant number of deep excavations within
varying soil types, as well as tunnelling under live railways and heritage buildings. From the onset of
the project, significant effort and planning was put into geotechnical instrumentation and monitoring,
with over 5200 instruments being installed during the life of the project over a length of less than 3
kilometres. This paper details the initial planning and management process, as well as the contractual
requirements, which formed the basis for more instrumentation as the project progressed. Specific
project requirements such as compensation grouting under buildings and tunnelling under live
railways at depths of less than one tunnel diameter required specific planning measures and additional
detailed monitoring which is discussed herein.
A large number of automated instruments were used to ensure cost effective and safe collection of
data. The types of instruments used on the project are discussed in detail with respect to their
applicability, accuracy, reliability, repeatability and cost effectiveness. Examples are presented to
illustrate the above points as well as highlight operational issues learnt. The process of data collection,
management and reporting is also discussed.
With construction taking place in a variety of ground conditions ranging from very soft alluvial silts
and reclaimed fill to medium dense alluvial sands and stiff clays a number of distinct response issues
were observed by the monitoring. The lessons learnt from three years of continuous monitoring of
ground and building movements, groundwater movements, and instrument vibrations are discussed
with respect to this project and future projects in Perth within similar geotechnical environments.
Detailed examples of ground, sheet pile and wall movements and strut loads with respect to excavation
design are presented, along with examples of the exceptionally low volume loss from TBM operation,
and resulting building responses to ground movement. An empirical method for predicting ground
settlement due to sheet pile extraction is also presented. Examples of ground vibrations induced by
sheet piling, construction activities and tunnelling are presented.

2. 1 INTRODUCTION
The minimum required instrumentation for the project was specified in the contract documents
referred to as the Scope of Works and Technical Criteria (SWTC), which became the guiding
document for tendering purposes and initial estimation. To address the definition of purpose for
monitoring, a Building Protection Management Plan was created by Leighton Kumagai Joint Venture
(LKJV). The overall purpose of LKJV’s approach to instrumentation, monitoring and building
protection was summarised in the Management Plan as follows:
“ to identify the controls to be implemented to ensure personal safety (construction and public),
and verify design predictions to prevent damage to buildings, services and civil infrastructure as a
result of LKJV construction activities.” [From LKJV’s “Building Protection Management Plan”]
Appropriate management methods were also created and put in place to handle the possible influences
of construction activities due to the soft Perth soils. This included selecting “fit-for-purpose”
instrumentation that was able to be monitored safely, whilst still providing accurate and timely
feedback about construction progress. In addition to working in, with and around the construction
personnel, a key criteria was to minimise disruption to pedestrians, traffic flows, and retail business in
the CBD.
2 INITIAL PLANNING AND MANAGEMENT PROCESS
2.1 Overview
The need for protection of workers’ safety, property and the environment was foreseen by the Public
Transport Authority (PTA) in their tender scope document “Scope of Works and Technical Criteria”
(SWTC). These activities included:
• Monitoring the performance of deep excavations with respect to design;
• The need for controls to minimise the potential for damage to buildings, services, roads, rails
and bridges from construction activities such as:
- demolition;
- sheet piling, bored piling or diaphragm wall construction;
- tunnelling;
- ground improvement activities (jet grouting, soil mixing, compensation grouting);
- consolidation from groundwater drawdown.
• Determining a series of baseline condition surveys to objectively determine any damage;
• A process for receiving automated alerts if movement criteria were exceeded.
On consideration of the complexity of the final monitoring program, LKJV added the following
additional elements to those listed in the SWTC:
• An overall management process to coordinate the activities of design, construction, survey
and monitoring crews, with geotechnical and management reviews. A single document
(Building Protection Management Plan) was created to bring together the requirements of:
- Geotechnical Interpretive Report;
- Ground Settlement, Building Protection and Repair Plan, incorporating Property
Condition Surveys and Building Protection Assessments;
- Instrumentation and Monitoring Plan;
- Various area-specific Method Statements and Safe Work Methods (i.e., JSA’s);
- Feedback from the actual results generated.
• Visual approach to interpretation of monitoring data to allow for quick interpretation by a
range of personnel;

3. • Innovative instruments and monitoring methods such as wireless electrolevel beams and
terrestrial photogrammetry driven by safety or minimising disruption to the public;
• Emergency Response procedures as part of the overall risk management plan to cover the
event of a massive failure.
Figure 1 outlines the key elements of the building protection and monitoring process.
Geotechnical investigations
Condition surveys in
zone of influence
Detailed
design
Assess the need for
building protection
Install instrumentation Protection of key
and monitoring structures Construction
and
Tunnelling
works
Investigate
exceptions
Post construction
surveys and repair
Figure 1. The LKJV Building Protection and Monitoring Process
2.2 Damage criteria
After extensive preliminary geotechnical work had been undertaken, modelling of the potential zone
of influence of the project works was performed. This determined the width of the potential
subsidence zone, based on the predicted design level of induced settlement and TBM face loss.
A key point to note is that although the Ground Settlement, Building Protection and Repair Plan
determines a zone of influence based on a designed level of settlement caused by the excavations and
the TBM, the actual performance of the TBM was expected to be considerably better than this (i.e.,
less settlement). This was in demonstrated by the actual TBM operations, where up to 20mm was
designed for along William Street, but only around 3-5 mm was observed. The performance of the
TBM with respect to design is discussed in more detail later in this paper.
Once the potential zone of influence was determined, a visual Property Condition Report was prepared
for each of the following structures along or adjacent to the route of the project:
• 88 buildings, from single storey to BankWest tower;
• 5 bridges and footbridges, including the heritage listed Horseshoe Bridge;
• Sections of roads and associated furniture along and adjacent to William and Roe Streets;
• Around 30 water and sewer services using a CCTV camera.
The design level settlements of the TBM had the potential to cause minor damage to some buildings
along the route. An engineering assessment was made to determine whether this potential damage
would exceed the limits specified in the PTA’s SWTC. The damage criteria was based on the work of
Boscardin and Cording, 1989, which is reproduced as Table 1.

4. Table 1 - Building Damage Classification
Approx.
Description of Max
Risk Description of Typical Damage and Likely Crack
Degree of Tensile
Category Forms of Repair width
Damage Strain [%]
[mm]
Less than Less than
0 Negligible Hairline Cracks
0.1 0.05
Fine cracks easily treated during normal
redecoration. Damage generally restricted to
0.05 to
1 Very Slight internal wall finishes Perhaps isolated slight 0.1 to 1
0.075
fracture in building. Cracks in exterior
brickwork visible upon close inspection.
Cracks easily filled. Redecoration probably
required. Recurrent cracks can be masked by
suitable linings. Exterior cracks visible: some 0.075 to
2 Slight 1 to 5
repointing may be required for weather- 0.15
tightness. Doors and windows may stick
slightly.
Cracks may require cutting out and patching.
5 to 15 or a
Tuck pointing and possibly replacement of a
number of
small amount of exterior brickwork may be
3 Moderate cracks 0.15 to 0.3
required. Doors and windows sticking. Services
greater
may be interrupted. Weathertightness often
than 3
impaired.
Extensive repair involving removal and
15 to 25
replacement of sections of walls, especially over
but also
doors and windows required. Windows and door Greater
4 Severe depends on
frames distorted. Floor slopes noticeably. Walls than 0.3
number of
lean or bulge noticeably. Some loss of bearing in
cracks
beams. Services disrupted
Usually
Major repair required involving partial or greater
complete reconstruction. Beams lose bearing, than 25 but Greater
5 Very Severe
walls lean badly and require shoring. Windows depends on than 0.3
broken by distortion. Danger of instability. number of
cracks
For each property, a Building Protection Assessment was undertaken by Airey Taylor Consulting that
considered the predicted maximum damage from the Ground Settlement Plan and the cumulative
variation from the initial damage category assessed in the Property Condition Report. The result was
the maximum damage category that could be expected. Building protection was required if the
“incremental” damage exceeded the following limits:
• For heritage structures – very slight (up to 1mm crack width);
• For other structures – slight (up to 5mm crack width).
In addition to compliance with the PTA’s SWTC, a formal Instrumentation and Monitoring Plan was
produced to detail the network of devices which would provide feedback for the following:
• Construction management to ensure the safety of deep excavations is maintained;
• TBM operators and management to control the various TBM operating parameters;
• Geotechnical Manager to ensure the project’s impact on the surrounding natural and built
environments is minimised and within stated limits.

5. 3 KEY AREAS OF MANAGEMENT FOCUS
In addition to the minimum contractually-specified arrays, there were a number of key construction
activities that needed specific management requirements:
• Protection of key structures: A number of structures, buildings and services needed
special treatment due to their calculated risk category. All other structures were monitored
according to the Instrumentation and Monitoring Plan to confirm the validity of the design
assumptions.
• Incident and emergency management: With the extensive array of monitoring devices,
LKJV needed a documented process to investigate any devices that showed movement “out
of tolerance”, plus planning for major high risk events.
These two areas are discussed in more detail in the following sections.
3.1 Protection of key structures
The main structures that needed unique building protection solutions were:
• Underpinning of the Wellington Building
• Removal of the Mitchell Façade
• Protection of the Horseshoe Bridge arches
• Compensation grouting of the buildings under which the TBM passed
• Perth Rail Yard, footbridge and station platforms (where tunnelling under the live railways
was at depths of less than one tunnel diameter)
• Claisebrook Sewer.
These are each discussed briefly below.
3.1.1 Underpinning of the Wellington Building
The heritage-listed Wellington Building is a “classic piece of turn of the 19th century corner
architecture” under which the new station had to be constructed. As part of the permanent station
structure, the Wellington Building had an array of tubular steel and grout micropiles drilled from
within the basement. A concrete slab was then poured in the basement but not connected to the
micropiles. A series of flat jacks were placed between the top of the micropiles and the base of the
concrete slab. The slab was then clamped to the external diaphragm walls, thus forming the roof of
the new station. Excavation was then commenced in a top down method under the Wellington
Building, with the former footings removed with the first level of excavation, and the weight of the
slab and building supported by the micropiles and the diaphragm wall. The excavation was then
completed to base slab level and the tubular steel piles were then cut, and tied into the base slab of the
station providing an uplift anchor. The weight of the building then sat on the roof slab of the new
William Street Underground Station. (WSS)
To monitor the impact of the construction works, around 40 optical prisms were placed around the
building and read from robotic theodolites on the Advertising Tower at Perth Station, and the Post
Office Building in Forrest Place. This allowed for remote monitoring and interpretation of movements
across the building. Being heritage listed, the damage criteria were stricter for the Wellington
Building, which meant a much higher density of micropiles were necessary than would be required on
a purely structural basis. Additional manual monitoring such as roof and building levelling, tilt
monitoring and retro target surveying was undertaken to enhance the automated monitoring.

6. Figure 2 - Wellington Building, and Excavation of Exterior Brick Wall of Building Prior to Tieing
Basement Slab and Capping Beam to Diaphragm Wall
3.1.2 Removal of the Mitchell Façade
Only the façade of the Mitchell Building was heritage listed, but it was located very close to the
diaphragm wall alignment for the station. This combined with safety concerns over the stability of the
façade’s render meant that LKJV sought permission from the Heritage Council to remove the façade
to ensure its protection. Permission was granted and the façade was encased in a steel frame and cut
into pieces to be stored off site, as illustrated in Figure 3.
Figure 3 - Mitchell’s Building Prior to, and during breaking up into pieces
3.1.3 Protection of the Horseshoe Bridge
LKJV’s first consideration for the Horseshoe Bridge was full underpinning through installation of jet
grout columns under the existing footings. However after more detailed analysis of the structure, the
potential for differential movement across the structure was still highly probable. It was determined
that due to the flexible nature of the steel-framed structure there would be no structural damage, but
the façade heritage features (cement render arches) were susceptible to movement and needed to be
propped with timber arches to prevent damage.
3.1.4 Compensation grouting of the “Gold Group”
The “Gold Group” buildings (named for their importance to the project) comprise the following
buildings facing William Street between Hay and Murray Street Malls: Friendlies Chemist, HBF,
Hungry Jack’s/KFC, Walsh’s Building (McDonalds, and other retail tenancies).
The route of the TBM passed either partially or wholly under these buildings, and LKJV’s Building
Protection Assessment indicated the need for protection, with a potential design movement of 20mm.

7. Due to various space and access constraints, LKJV determined the best option was to work
collaboratively with Keller Ground Engineering and implement a TAM compensation grouting
system. The details of this system are described in more detail in another paper contained herein by
Nobes & Williams (2007)
3.1.5 Perth Rail Station tracks and platforms
The TBM passed twice underneath the station and the live railway, which needed to be kept running at
all times. Due to the flexibility of ballasted rail, there was no structural problem should TBM
settlements reach the design limits, but such settlements may cause two operational issues. Firstly, if
tilting of the platform edge increased relative to the track there would be insufficient clearance for the
train, and secondly, if excessive cross cant was to occur it may lead to a derailment.
Due to the success of the first stage of tunnelling up William Street (maximum 5mm settlement), it
was determined that an observational approach be taken in preference to preventative measures, with
defined management methods and actions. Elements of this observational method included:
• Automatic electrolevel beams on the rail tracks;
• Automatic tilt meters on the platform faces;
• High density of surface, building and rail settlement points;
• 24 hour/7 day week survey, with rail safety presence, and direct ring-by-ring contact with the
tunnel shift engineer;
• Specific management measures including:
- A purpose-written Method Statement covering survey, interpretation, tunnel operations
and rail safety;
- Daily coordination meetings with all parties (management, survey, geotechnical, tunnel,
rail and client);
- Web-based access to all monitoring information for all teams;
- Emergency scenario workshops.
The close contact with the TBM crew allowed for parameters to be changed on a ring by ring basis on
the survey and automatic results presented. The result was that during the passage of the TBM, the
maximum final rail movement was limited to less than 10mm.
3.1.6 Claisebrook Sewer
With the footings of the century old, brick lined, Claisebrook Sewer potentially lying within 800mm
of tunnel alignment, protective measures were required. After thorough discussions with Water
Corporation, it was decided to re-line the inside of the sewer with new plastic piping. In addition to
this, LKJV determined that since a subsidence risk was still present during the passage of the TBM
due to fragile nature of the sewer, LKJV also temporarily “over-pumped” the sewer when the TBM
was within a zone of influence.
3.2 Incident and emergency management
3.2.1 Incident investigations
All instruments had the following three alert levels determined in the Ground Settlement and Building
Protection Plan:
• Trigger, set at say, 80% of the “design” level as an early warning;
• Design, equal to the predicted movement level;
• Allowable, set at say 120% of the “design” level and at which remedial action must be taken.

8. For all instruments, these alert levels were entered into the instrument database (GIMS). If a level was
exceeded, an SMS and email were sent to a nominated group of people to action as appropriate. When
alert levels were exceeded, a rigorous process was followed to ensure traceability of all decisions.
This process is shown in Figure 4. If the alert was not spurious, or a transient event, a more detailed
investigation was initiated to determine whether any changes to design or construction techniques
would be necessary.
• Monitoring frequencies were set for each instrument, and one full time person was dedicated
to ensuring the instruments being read matched the progress of the construction works.
During the peak months, a team of up to 19 people were dedicated to gathering, inputting,
reviewing and investigating monitoring data:
3.2.2 Emergency management through desktop scenarios
Although the chance of an excavation or TBM failure (to a level requiring the assistance of emergency
services) was remote, as a key part of the LKJV’s risk management approach, a comprehensive
emergency management process was implemented. To test our management plan so that it was a
“live” document, we undertook a series of scenario workshops both internally and externally to LKJV.
On 1 December 2005, around 40 representatives from LKJV, Leighton Contractors, Leighton
Holdings, New MetroRail (client), Public Transport Authority (operations and infrastructure), City of
Perth, Fire & Emergency Services Authority, Police, Worksafe, Western Power, Alinta Gas, Water
Corporation, Telstra and Main Roads attended a workshop focussing on the bored tunnel section up
William Street. One of the key findings to come from the scenario workshops was that of the role of
the Hazard Management Authorities (HMAs) and how to use the existing Memoranda of
Understandings between the HMAs and the various government and private agencies.
Another workshop was held on 15 March 2006 with a similar range of external parties, but with more
attendance from railway operations personnel, which was the focus of the day. Also a number of
internal scenario sessions were held with teams from survey, geotechnical, tunnel and rail to ensure
coordination of activities and communication. We also checked that our communication protocols
were consistent with Leighton Contractors national approach to Crisis Management, and sought
feedback from Leighton Holdings on lessons learnt from recent crisis management activities (Lane
Cove Tunnel). Feedback from all sessions was used to make our procedures as user friendly as
possible. The aim was to ensure people knew what to do if something escalates from an incident to an
emergency.
A Building Access Checklist was also obtained for every property, which LKJV could use to raise an
alarm in the case of an emergency. Since LKJV’s monitoring and/or tunnelling teams will probably
be the first to know of any incident, we determined that having this information on hand was prudent.

9. BUILDING AND MONITORING INCIDENT FLOWCHART
NEW METRORAIL CITY PROJECT
Legend 1 Point of Contact
Point of Contact (PC)
Incident occurs Primary Secondary
PC Point of Contact Building Incident
Primary Contact Alternative Contact
Peter McGough Kate Stone
Buiding Incident Matt Williams Kate Stone
IM I & M Manager Monitoring Incident Peter McGough Fugro
Monitoring Incident Peter McGough Franco Roselli
PD Project Director 2
Infrastructure /
Infrastructure/Services Mike Wallis Area Manager
CM Construction Manager Services IncidentMichael Wallis
Incident Relevant Area Manager
3
AM Area Manager No further action No Is investigation
GM Geotechnical Manager (Update register if required? Considerations
DM Design Manager required)
Establish whether incident is legitimate
Yes Considerations
Form W1114-CS-4018 1. Notification to Area Manager
4 2. Safety of personnel
Record Incident on
3. Structural integrity of building/infrastructure/service
register and review
4. New occurrence or sudden change in trend
details
5. Compare to existing condition, historical monitoring/reports
BUILDING INCIDENT RESPONSE and any background data
PC
CONTACT DETAILS 6. Review of recorded levels against control levels
LKJV M ANAGEMENT CONTACTS TELEPHONE MOBILE 7. Visit to location and visual inspection
5
Rob Wallwork Project Director 9424 5604 0411 259 451 8. Estimate of damage
Conduct preliminary 9. Record of construction work being undertaken at time of
Tony Cariss Construction Manager 9424 5515 0419 932 132
investigation incident
K. Akabane Ass’t Construction Mgr 9424 5596 0421 404 984
Kate Stone Community Relations Mgr 9424 5588 0422 001 037 PC
6
F. Aikawa Design Manager 9424 5563 0422 246 067
Simon Gegg William Street Station Mgr 9424 5506 0402 898 627 7
Paul Farris Southern Area Manager 9424 5631 0422 001 235 No Site assessment by GM to
Is further action
agree and implement
Ashley Warner Perth Rail Yard Manager 9228 4942 0421 144 469 required?
Yes - URGENT action plan
LKJV TUNNELLING CONTACTS TELEPHONE MOBILE
Henry Yamazaki Tunnel Manager 9424 5654 0422 593 780
Frank Hannagan Tunnel Superintendent 0421 053 317 GM/PC
Yes
Frank Bonte General Foreman 0421 053 313 8
S. Shigemura Senior Engineer 9424 5653 0422 653 574
M. Oshima Senior Engineer 9424 5691 0413 197 300
Are only minor
Andrew Shepherd Shift Engineer – Tunnel 9424 5651 0411 659 546
Yes repairs required? Special Response Team
T. Watanabe Shift Engineer – Tunnel 9424 5651 0431 120 366
Special Contracts Manager/Nominee
Tom Jones Shift Engineer – Tunnel 9424 5639 0422 001 021
Area Manager/Nominee
TBM Direct Line 9202 1485 No Geotechnical Manager/Nominee
LKJV MONITORING & GEOTECHNICAL CONTACTS TELEPHONE MOBILE LKJV geotechnical/monitoring rep
Peter McGough Instrumentation and LKJV Subontractor respresentative
9424 5519 0421 053 351 9
Monitoring Manager PTA Representative
Complete Incident
Oskar Sigl Geotechnical Manager 9424 5514 0411 659 549 Form to initiate Form W11140-CS-4019
If available:
Intern’l: +65 9735 2522 AMBER warning
Construction Manager
Marc Woodward Geotech Manager (alt) 9347 0000 0417 911 131 Assistant Construction Manager
PC
Barry Hackett Building Protection Eng. 9424 5511 0421 053 337 Design Manager/Nominee
10
LKJV R AIL CONTACTS TELEPHONE MOBILE Project Director
Notify PTA (& insurer)
Peter Rosenbauer Senior Project Eng’r - Rail 9424 5509 0402 894 801 immediately after
Vasil Calcan Senior Rail Safety Officer 0421 635 8491 initiating amber
Peter Russell Rail Safety Officer 0407 193 915 warning
John Welch Rail Safety Coordinator 9424 5541 0421 711 303 PC/GM Investigation considerations
FUGRO CONTACTS (INSTRUMENTATION & MONITORING) TELEPHONE MOBILE 11 1. Notification to Area Manager
Fugro Monitoring Phone 9424 5617 0439 930 927 Undertake detailed 2. Safety of personnel
investigation and 3. Structural integrity of building, infrastructure, or
Ritchie Mulholland Chief Monitoring Surveyor 9424 5617 0417 611 295
formal risk service
Home: 9302 6256 assessment 4. Review of predicted settlement and
Kent Wheeler Monitoring Surveyor 9424 5584 0400 980 060 GM/PC/AM construction impact
PTA CONTACTS TELEPHONE MOBILE 15 5. Quantification of damage
12 6. Review protection works to determine
Richard Mann Project Director 9326 2536 0419 964 209 Notify PTA (& insurer)
Verify short term adequacy
Eric Hudson-Smith Geotechnical Manager 9326 2060 0419 988 861 immediately after
remedial action 7. Undertake condition survey to determine extent
initiating red alert
Jock Henderson Special Projects Manager 9326 2093 0419 915 408 closed out of damage
PD/CM/GM
INSURANCE CONTACTS TELEPHONE MOBILE GM/AM 8. Undertake additional monitoring (eg survey) to
Bob Perry Marsh Ltd 9421 5666 0414 307 247 13 quantity and monitor further damage
9. Complete risk assessment
EMERGENCY CONTACTS TELEPHONE TELEPHONE
14 10. Review of incident impact on both
PTA Urban Train Control 9326 2214 Can incident No
Initiate RED alert via temporary and permanent works design
Main Roads Traffic Operations Centre 9428 2222 be resolved? Incident Form and construction
Fire and Emergency Services (FESA) 000 1300 1300 39 PD/CM/GM
State Emergency Services (SES) 9277 0555 Action considerations
1. Increase monitoring
FESA and SES Operations Centre 9323 9333 9323 9322
Yes 2. Continuous monitoring
WA Police 000 9222 1111 3. Review construction techniques and equipment
Russell Armstrong (Incident Management 16
9222 1694 9222 1958 Verify long term 4. Review emergency procedures
Unit and LEMC) 5. Review geotechnical control limits
remedial action
Ambulance 000 6. Determine whether amber warning or red alert
closed out
Bill Thompson 0415 428 617 required
GM/DM/CM
Worksafe 9327 8777 1800 678 198 7. Stop work where required
8. Determine urgency of repair work
City of Perth 9461 3333 17
Police Post at City of Perth 9325 6000
Bill Strong (LEMC) 9461 5836 0418 947 908 No
Repairs
Sadak Hamid 9461 3885 0417 977 101 required?
Transperth 131 608 9325 2277
Alinta 131 352
Amcom 1800 222 019 Considerations
Yes 1. Identify scope of repair work
Optus 131 344
18 2. Establish programme for repair work
Telstra 132 203 Seek authorisation 3. Obtain quotes
Water Corporation 131 375 for repairs 4. Advise PTA
George Basanovic 9386 4952 0417 180 677 CM/PC 5. Advise Insurers
Western Power (generation) 131 351 6. Obtain property owner/representative approval to do work
Shane Duryea 9427 4257 0407 445 076 19
Undertake repairs
Synergy (retail)
Business Faults 131 354 CM
Residential Faults 131 353 Considerations
20
Final inspection and 1. Complete "During-construction property condition survey"
sign off 2. Issue copy of survey and incident report to PTA and obtain
CM/PC property owner/representative sign off.
21
Close out incident Form W1114-CS-4019
SCM/PC Form W1114-CS-4018
22
Notify PTA of close
out
SCM
Figure 4 - Incident Notification and Investigation Process

10. 4 INSTRUMENTATION AND MONITORING
4.1 Instrumentation Quantities
A total of 5205 instrumentation points were installed on the New MetroRail Project to monitor the
influence of excavation, tunnelling, piling and dewatering activities. The instrumentation types, and
quantities installed over the life of the project are summarised in the following table.
Table 2 – Instrument Types and Quantities
Instrument Type Quantity Installed
Surface Settlement Pin – SSP-1 1021
Surface Settlement Retro – SSP- 2 451
Bored Settlement Point – SSP- 3 559
Deep Settlement Point – SSP- 4 19
Building Settlement Point - BSPB 449
Building Settlement Retro - BSPR 1403
Building Settlement Prism - BSPP 285
Tilt Meter, Manual - TILTM 54
Tilt Meter, Automatic - TILTA 33
Crack Meters – CM 82
Electro Level Beams - ELB 150
Strain Gauges – SG 174
Vibration Sensor - VS 12
Inclinometers - INCL 64
Extensometers, Magnetic - EXTM 187
Extensometers, Rod - EXTM 25
Vibrating Wire Piezometers - VWPZ 91
Open Hole Piezometers - OHPZ 146
5205
In addition to the above, a further 180 recharge and dewatering bores were drilled on the project, most
of which were also regularly monitored for water levels.
The instrumentation density installed on the project was considered to be high, with densities being
consistently higher than minimum specifications, however a large proportion of the manual settlement
points (SSP-1 and SSP-3) required replacement and thus approximately 800-1000 of this number was
likely to have been a replacement for points damaged by the construction process. Despite the high
quantity of instrumentation, costs for instrumentation and monitoring including drilling remained very
low at approximately 3-4% of the tender price.
4.2 Instrumentation Types
The 18 types of instruments used on the project could be grouped into 7 functional types as follows:
• Vertical Ground Movement
• Lateral Ground Movement
• Building Movement
• Building Tilt
• Structural Response
• Vibration
• Groundwater Movement

11. The instruments used in each of the functional groups, their suitability for purpose, reliability,
accuracy, repeatability, and cost effectiveness are discussed in detail in the following sections:
4.2.1 Vertical Ground Movement
Ground Movement, (settlement and heave) was measured using the following instruments:
• Settlement Pins (SSP-1), [survey nails and bridge spikes installed in roads, bridges and
footpaths]
• Settlement Points (SSP-3), [steel reinforcing rods grouted 800mm deep into a borehole]
• Deep Settlement Points (SSP-4), [steel reinforcing rods grouted into borehole approximately
1.5m above services]
• Rod Extensometers (EXTR),
• Magnet Extensometers (EXTM)
• Reflective Photogrammetry Targets
• Electrolevel Beams
• Retro Targets
Settlement pins, settlement points and reference head on the rod extensometers were all measured by
means of digital levelling using a Leica DNA-10 Digital Level and Barcode Staff. Typically traverses
of up to several hundred metres were undertaken without control points. A misclosure limit of 3mm
was used as the acceptance criteria for these traverses. The repeatability of surveys was within +/-
1.5mm of the true or mean level as illustrated by Figure 5, which was a point sufficiently away from
all excavation and tunnelling that no settlement occurred. Vibration from pedestrian traffic and
machinery was a common problem, due to the city location, with shaking of the digital level visible
through the optical sight. This vibration occasionally resulted in gross errors, which were much
greater than +/- 1.5mm.
Raw survey data downloaded from field was adjusted via the least squares method. Data was then
“dumped” into excel spreadsheets for verification. Verified data was then exported to GIMS database
for permanent record. Contouring or cross sectioning of data was then undertaken. Whilst apparently
tedious, the above method enabled easy verification and manipulation of large quantities of data
without impacting on the integrity of the raw database. Typical examples of sectional and contoured
output are shown in Figure 6 and Figure 7.
The deep settlement points drilled into the ground (type SSP-3 and SSP-4) typically showed less
fluctuations than the smaller survey pins and spikes (type SSP-1) hammered into the ground and thus
were considered more reliable. The results on the project indicated that there was no discernible
difference in the total measured movement between points installed through road pavements (type
SSP-3) and those installed at the surface of the road (type SSP-1), inferring that the road base was
flexible enough to reflect the ground movements occurring at subgrade level, even where asphalt
thicknesses of 100-200mm were found along William Street.
An innovative drilling method was used to install settlement points in areas where coring of the upper
materials was not required. Drilling via vacuum extraction was used to install SSP-3’s and SSP-4’s in
many areas. The method simply involved the use of a pipe connected to suction truck, which
vacuumed up the sands, thus forming a hole, as illustrated in Figure 8 and Figure 9. The method is
normally used in Perth to locate and expose buried services, but we found it was ideally suited to our
purpose of forming shallow holes in a very quick and cost effective manner with no preparation or
clean up required. The shallow holes were formed within a few minutes, with the installation of the
grouted steel settlement rods occurring immediately after hole drilling, thus the whole process was
typically complete in 10-15 minutes.

12. 13.815
SSP_0533 Reduced Level
Reduced Level (mAHD)
13.805
13.795
26-Oct-04
25-Dec-04
23-Feb-05
24-Apr-05
23-Jun-05
22-Aug-05
21-Oct-05
20-Dec-05
18-Feb-06
19-Apr-06
19-Jun-06
18-Aug-06
17-Oct-06
16-Dec-06
Figure 5 – Example of Repeatability of Settlement Point
Ground Movement Profile Due to Tunnel 2 Excavation - CH 440 PMup
(Chainage: 440 PMup +/- 10m, Tunnel 1, Vs = 0.00% Tunnel 2, Vs = 0.60%)
15.0
10.0
5.0
0.0
Settlement (mm)
-5.0
-10.0 K=0.45
Vloss = 0.70% (320m radius of curvature)
(VLOSS = 0.60% if straight)
-15.0
-20.0
3/08/2006 8:00
4/08/2006 8:00
-25.0 5/08/2006 8:00
Tunnel 2 Cutter Face at CH 450 approx, 2/8/06 18:00
Tunnel 2 Cutter Face at CH 430 approx, 4/8/06 03:00 6/08/2006 8:00
Design Volume Loss Curve
-30.0
-35.0
-50.0 -40.0 -30.0 -20.0 -10.0 0.0 10.0 20.0 30.0 40.0 50.0
Chainage (m)
Figure 6 –Example Cross Sectional Display of Figure 7 –Example Contoured Output of
Tunnel Settlement with Time Settlement Data Around Major Excavation
Figure 8 – Vacuum Extraction Drilling Figure 9 – Vacuum Extraction Unit
Rod extensometers used on the project were the multiple head grouted anchor type supplied by Slope
Indicator Company (SINCO). The heads were typically grouted 1.5 and 4.5 metres above the tunnel

13. crown, and during tunnel passage the differential movement of the rods relative to the fixed head was
measured manually with micrometer. The results obtained were consistent with tunnel activities and
show that micrometer repeatability was approximately +/- 0.25mm, as illustrated in Figure 10, but
calculated total movements were limited by the head levelling repeatability of +/- 1.5mm.
The installation of the rod extensometers was a prescribed requirement on the project, with the benefit
of the installed rod extensometers being questionable as the results confirmed the knowledge that
relatively greater settlements occur at depth than at the surface. The density of the extensometers
installed (1 per 200m) served no other benefit than to confirm this fact, with the higher density of
surface monitoring providing a better warning of face loss or heave.
Rod 1 - Diff. from Original (mm) Rod 2 - Diff. from Original (mm)
Rod Head - Diff from original (mm) Surface Movement at SSP 3023
5.00
4.00
3.00
Heave from
tail void
Tunnel
2.00 grouting
Induced
(point 1.5m
Diff. from Original (mm)
Settlement
from crown)
1.00
0.00
-1.00
-2.00
-3.00
No heave at
surface
-4.00
-5.00
01/ Jan/ 06 08/ Jan/ 06 15/ Jan/06 22/ Jan/ 06 29/ Jan/ 06
Date
Figure 10 - Typical Example of Rod Extensometer Figure 11 - Typical Example of Magnet
Output Data Extensometer Data
Magnet extensometers were used adjacent to excavations in preference to rod extensometers. The
type of magnets used on the project consisted of magnetic strips attached to corrugated plastic pipe,
which slid over standard inclinometer piping. The magnets were installed at intervals of 3-5m down
the inclinometer hole. The inclinometer and magnet were then grouted into place, initial readings
taken; a period of equalisation (~30 days) was then foregone before secondary readings were taken.
Readings were taken via lowering a probe down the centre of the inclinometer pipe until it reaches the
bottom magnet position. The tape is then pulled up and as it passes each magnet, two beeps are heard;
the depth at which the second beep is heard is recorded for each magnet. The method is prone to gross
errors. The repeatability of the measurements is approximately +/- 5mm as illustrated in Figure 11,
with gross movements with depth clearly visible once excavation induced settlement commences. The
settlement of the top of the inclinometer was also checked via regular levelling and compared to the
observed results. The magnet extensometers were considered highly suitable for the intended purpose
of measuring large movements where accuracies of +/- 5mm were acceptable. Magnet extensometers
provided a cost effective solution without the need for multiple boreholes or expensive rod
extensometers, or alternatively they provided additional information at minimal cost from an existing
planned inclinometer. Experience from this project would suggest that at least 5 readings be taken to
establish an average baseline value before any excavation or external loading commences.
Settlement monitoring was also undertaken with retro reflective targets located on rail tracks or survey
spikes in areas where access for regular levelling was not possible. This method of survey was
undertaken using Leica Total Stations and was slightly less repeatable than digital levelling, with
higher degrees of scatter in the measured results. Repeatability using this method was in the range of
+/-2mm. This reduced repeatability is likely to be a result of human error as the surveyor focuses on
the centre of the target to get the correct result. As discussed later in the building monitoring section,
the effect of one or two face readings is also likely to have impacted on the repeatability of the results
obtained from this type levelling.
Due to the need to focus on the target, the resulting retro target survey is slower than compared to
digital levelling. However as this method only requires one surveyor for the majority of the survey,
the operational costs incurred can be less than or equal to digital levelling in many cases. Experience

14. on the project indicates that using retro targets for long term settlement monitoring should only be
considered where access is limited for level surveys, or where automated instrumentation cannot be
installed. In contrast, for short term high density monitoring of restricted access areas, retro targets
would provide a cost effective solution as they only cost a few dollars each to supply and install, and
the degree of repeatability can be negated by small traverse lengths and high frequencies of
monitoring.
Figure 12 - EL Beams installed along centreline of Figure 13 - Proximity of Retrieval Box Excavation
active rail line to Active Rail Line
Automated Electro-Level (EL) Beam monitoring was also used to monitor settlement of the train
tracks as excavation and tunnelling occurred in the Perth Rail Station and Perth Rail Yard. EL Beams
were required as access to the active rail area was limited with trains operating 18-20 hours per day,
and excavation was occurring within 1m of active tracks (Figure 12 and Figure 13), and tunnelling
occurred directly below the active train lines of Perth Train Station. Chains of EL beams were used to
obtain settlement profiles along the centreline of rail tracks, and transverse movements were also
measured every few metres. The ends of each EL beam chain were regularly verified via levelling and
settlement profiles adjusted for end settlement if applicable. Some EL Beams were in place for almost
2 years, and despite the vibrations from regular train traffic (every 2-30 minutes), extreme heat, and
weather, the EL beams showed no creep effects, with the repeatability of the entire chain remaining in
the range +/- 1.0mm of a mean value. A typical settlement profile and the fluctuation in the readings
observed over a 6 hour period where no construction activity was occurring is shown in Figure 14,
illustrating the high degree of repeatability.
The EL beam results were also consistent with excavation and tunnelling activities, with retro target
monitoring undertaken during tunnelling confirming the accuracy of the individual EL Beams as
shown in Figure 15, as well as highlighting the immediate response of the ground/rail as the TBM
passed underneath the beam shown. The sub millimetre accuracy of individual EL beams was
highlighted in their ability to resolve the daily 2mm variation in track height due to thermal effects.
As a result of this EL beam monitoring, there was continuous train operation throughout the 3 years of
the project, even with excavations within 1m of active trains as illustrated in Figure 13.
An innovative method of settlement monitoring using photogrammetry and auto target recognition
software was trialled on the project. Reflective targets mounted on the sides of “Cat’s Eyes” on the
road above the tunnel, on kerbs and on buildings, were monitored for movement. The aim of the
photogrammetry was to reduce the time the surveyors were spending on William Street, which was a
busy one way street through the centre of Perth CBD. By using photogrammetry, thus reducing the
survey time on the road, the risk of injury to our surveyors was reduced significantly as normal survey
required a moving method of traffic management (cars with flashing arrow boards and surveyors
working in front) in order to maintain traffic flow. In addition to the safety risks, the reduced cost of
traffic management and survey time was a benefit of this method of monitoring.

15. Figure 14 - Typical Repeatability of EL Beam Located on the Railway (15min readings over 6 hr period)
Longitudinal Settlement - EL_001_5L01 at CH 23.143m
10
8
6
Cumilative Movement (mm)
4
2
0
-2
-4
-6
-8
-10
12-May-06
13-May-06
14-May-06
15-May-06
16-May-06
17-May-06
18-May-06
19-May-06
20-May-06
21-May-06
22-May-06
23-May-06
24-May-06
Cumilative Date EB 527 EB 526
Figure 15 - Comparison of EL Beam Data with Retro Target Surveying
The reflective targets were typically 15-20mm in diameter and glued to the side of the “Cat’s Eyes” as
shown in Figure 16. Additional points were also installed on the adjacent kerbs and buildings, as
illustrated in Figure 17. Once an initial photo model was generated (from multiple photos), software
automatically determined the location and change in movement of each reflective point in subsequent
photos, with each model only requiring four control points. The photogrammetry software used was
3DM Calib Cam by Adam Technology, with an example model with automated target points
recognised and labelled shown in Figure 18. Typically two photogrammetry surveys per day were
run, with greater than 100m of tunnel coverage in each photo model.
There was good correlation with manual level surveys as illustrated in Figure 19 (Note: SSP 3005 =
manual level, SSP 2317 – 2319 = Photogrammetry Level), however due to the low levels of tunnel
deformation in the study area there was insufficient data to confirm the repeatability of the system
relative to levelling. The system proved to be fit for purpose and has numerous applications for
monitoring of buildings and structures at low cost. The safety benefits of the system cannot be
understated as it significantly reduced the period the surveyors were exposed to life threatening
injuries such as being hit by a car. If adopted at the start of a project the quantities of building and
settlement monitoring surveys would be reduced significantly thus saving hundreds of thousands of
dollars annually to similar projects of this type.

16. Figure 16 - Reflective Target on Cat’s Eyes Figure 17 - Reflective Targets on Kerbs/Buildings
Figure 18 - Photogrammetry Model with Automatic Target Recognition Generated from Figure 17
432
4
434
2
Photogrammetry
Points
0 436
S ettlem ent [m m ]
-2
438
-4
Levelling 440
-6 Point
442
-8
-10 444
13/11/05 23/11/05 3/12/05 13/12/05 23/12/05 2/01/06 12/01/06 22/01/06
Date
SSP_3005 SSP_2317 SSP_2318 SSP_2319 #N/A
Figure 19 - Comparison of Photogrammetry Surveys with Level Surveys

17. Settlement monitoring was the most time consuming and costly exercise on the project. The cost of a
surveyor and assistant was approximately A$1500 per day over 2.5 years (approximately A$500,000
per annum per survey crew), and 2-3 crews were operating at most times throughout the project. In
addition to this, daily traffic control at A$1000-A$2000 per day was also required when surveying
above the tunnels, and on highly trafficked streets where excavation induced settlement was occurring.
Experience shows that substantial cost savings in survey would have been possibly gained in using
automated EL beams mounted below footpaths and roads given that each EL beam costs in the order
of A$2500-A$3000 for a 3m beam length.
The use of automated instruments would also have reduced the quantity of engineer supervision on the
project whilst providing highly desirable continuous information to tunnelling and construction
personnel. The density of EL Beam readings would also have benefited the end users, as readings
would be spaced at 3-5m intervals rather than the 12-25m centreline spacing than was only possible
with manual monitoring.
4.2.2 Lateral Ground Movement
Lateral ground movement was measured primarily through inclinometers installed adjacent
excavations and between tunnels. The lateral movement of several sheet piled structures and rail lines
was also measured using retro targets.
The inclinometers and casing used on the project were supplied by SINCO and were found to be
extremely reliable with approximately 8km of readings (spaced at 0.5m intervals) being undertaken
each week, or more impressively approximately 800,000 readings per year totalling over 400km.
During the 2.5 year monitoring period, only the wheels and springs required replacement once.
Repeatability of measurements in holes up to 40m deep was found to be less than +/-1mm over the
40m, and did not change throughout the project. The results obtained were consistent with
expectations, with the development lateral ground movements and ongoing creep consistent with
excavation activities.
Given the quantity of readings obtained by monitoring personnel and the high potential for back
injury, a simple extension piece which fitted over the quick connect collar of the casing was developed
at the start of the project. The purpose of the extension piece was to extend the reading height to
approximately waist height (as shown in Figure 20) reducing the need for bending over the hole
continuously as is the common procedure (as shown in Figure 21). As a result there were no recorded
back injuries or complaints from monitoring personnel over the life of the project despite the millions
of readings taken.
Figure 20 - Inclinometer Measurement with Figure 21 - “Normal” Inclinometer Measurement
Extension Piece to Waist Height requiring bending over the borehole
Automated Inclinometers (IPI’s) were also used on the project in high traffic areas where access for
periods greater than 5 minutes was not possible, or posed an unacceptable risk to monitoring personnel
safety. The IPI’s were used to monitor ground deformations between the two tunnels along William

18. Street, and in a bus lane adjacent a bridge founded on stone columns. The IPI’s generally performed
very well and produced excellent results, and were stable for periods of more than 1 year. The
response of individual sensors was excellent, with a repeatability less than +/-0.2mm as illustrated in
Figure 22 below, with the overall accuracy of a 24m chain approximately +/- 0.5mm as illustrated in
Figure 23. There was a small proportion of sensors that showed minor creep movements, however
these were replaced by the supplier under warranty. It should be noted that in Figure 23, the
temperature sensors recorded increased temperatures after the tunnel passed which was possibly linked
to the exothermic heat generated during curing of the tail void grout.
Sensor 1 Relative Movement From Bottom of Hole
(RL From -12.985mAHD to -9.985AHD)
5.0 24
Temperature Increase after Tunnel Passage
4.0 23
3.0 22
Relative Movement (mm)
2.0 21
Temperature (0C)
1.0 20
0.0 19
-1.0 18
Response to Tunnelling
-2.0 17
-3.0 16
-4.0 15
-5.0 14
04- 05- 06- 07- 08- 09- 10- 11- 12- 13- 14- 15- 16- 17- 18- 19- 20-
Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06 Jan-06
7Pt Moving Average Trendlines fitted to Data Date / Time
Figure 22 - Typical Repeatability of Individual IPI Sensor
BH 2178 A-Axis From Initial
20/01/2006 7:30
Chainage 261.57
15
18/01/2006 6:00
10 16/01/2006 6:00
14/01/2006 6:00
Reduced Level (mAHD)
5
13/01/2006 6:00
0
12/01/2006 6:00
Bored Tunnel Level 11/01/2006 6:00
-5
9/01/2006 6:00
-10
7/01/2006 6:00
-15 4/01/2006 6:00
-10 -5 0 5 10
West East Created: 20/01/2006 7:30
7Pt Average Cummulative Displacement (mm)
Figure 23 - Typical Repeatability of IPI Chain (for 16 day period shown in Figure 22)

19. Whilst expensive to install, the IPI’s are recommended for where long term monitoring of large
excavations is required in developed countries (i.e. cost of manpower is expensive). A typical 30
metre IPI and datalogging system may cost approximately A$20,000-A$25,000 to purchase, however
if that instrument is logged every two days over a period of 1 year, the cost of two monitoring
personnel to undertake the same manual inclinometer surveys would also cost in the region of
A$20,000 or more. Whilst the cost benefits are neutral over 1 year, the benefits lie in the continuous
information gained and ability to warn of impending failures at any time. Additional benefits are that
construction personnel can have unrestricted site access, allowing continuous traffic/machinery flow
above (assuming the instruments are located under 1m of fill), and importantly the IPI’s can be
retrieved and re-used at other locations thus reducing the overall cost for longer and larger projects.
The IPI’s were located in highly trafficked areas, and hence restrictions on installation time and area
available for drilling were present, so a drilling technique new to Australia; sonic drilling, was utilised.
Sonic drilling allowed rapid dry coring of the borehole from the surface, through 100-200mm of
asphalt, to depths of approximately 30 metres in one night. The continuous coring was of great benefit
in geological logging, whilst the dry drilling method was very beneficial environmentally as no sumps
or mud tanks were required to contain wash cuttings, thus also saving valuable clean up time. The
machine used was also compact and thus traffic management was confined to two lanes, and the IPI
installation was completed in one night. The cost savings compared to traditional rotary methods were
substantial. The sonic core method was also used to drill and install SSP-3’s and Rod Extensometers
above the tunnel centreline, and to sample jet grout and soil mix columns. The method allowed rapid
coring (in the order of a few minutes) through the thick surface asphalt and crushed rock road base
into the subgrade, with the machine quickly mobilised to the next drill location in 5-15minutes.
Figure 24 – Sonic Drill Rig in William Street Figure 25 – Sonic Rig Showing Coring Barrel and
Catch Tray for Water from Core Barrel
4.2.3 Building Movement
Building movement (settlement and heave) was monitored using the following instruments:
• Building Settlement Points (BSP), [bolts installed into buildings, bridges and structures]
• Retro-Reflective Targets (BSPR)
• Optical Prisms (BSPP)
• Reflective Photogrammetry Targets
• Electrolevel Beams