Torino Metro Experience

Post Graduated Master Course
TUNNELLING AND TUNNEL BORING MACHINES
Subject of the lesson : Torino Metro Experience
Lecturer : Piero Sartore, Giovanni Giacomin, Giorgio Fantauzzi
Golden Sponsors
POLITECNICO DI TORINO
Golden Sponsors
Sponsors
Academic Year: 2009-10

Piero Sartore
Project Management & Construction - Infrastructures & Civil
Head of Departement (Tecnimont S.p.A. - Maire Tecnimont Group)
EXCAVATION MANAGEMENT IN TORINO METRO
Post Graduate Master Course
Giovanni Giacomin
TBM & Tunneling Departement Director (Ghella S.p.A.)
Giorgio Fantauzzi
Project Leader (Tecnimont S.p.A. - Maire Tecnimont Group)
Turin, 23 March 2010

Torino Metro Line 1 : General description
GTT is the concessionary for design, construction
and management of the Metro Line 1, one of the
main infrastructures in the public transportation
plan for the Torino area.
The civil works design was governed by the VAL
(Automated Light Vehicle) system characteristics.
The train is 2.08 m wide, 52 m long and its
maximum passenger capacity is 440 people (6
pass./m2).
Base on width of train, a single 6.8 metre diameter
Base on width of train, a single 6.8 metre diameter
circular tunnel contains the double track line has
been chosen.
The tunnel was bored by TBM.

Tunnel 3.000 m tunnel bored using a TBM EPB (earth pressure
balanced shield machines)
Stations 6 stations cut & cover with diaphragms. First station
(Marconi) was TBM job site and the last (Lingotto) with train
interchange.
5 aeration shaft connecting surface and tunnel.Shaft

ASPECT TO MANAGE:
1. Type of Contract;
2. Procurement;
3. Design Process;
4. Public opinion;
5. Legislative conditioning;
6. Environmental requirements;
7. Executions of works;
8. Design.

1. Type of Contract
Contract Time Schedule
Procurement and Construction.
Contract Milestones
T0 – Start works – 08.01.2007
T1 – Areas modifications and mitigations – 10.01.2007
T2 – Access est Carducci – 06.07.2007
T3 – TBM Assembly – 23.01.2008
Bid Procedures: 05.2006 – 07.2006
Client analysis: 07.2006 – 10.2006
Notice award: 12.2006
Contract sign: 20.12.2006
Contract start: 07.01.2007
T4 – Finishing tunnel Marconi-Carducci – 23.06.2009
T5 – Finishing tunnel Carducci-Lingotto – 12.10.2009
T6 – Finishing Carducci and transitability Marconi,
Nizza, Dante & Spezia, PL2, PL3, PL4, PL5, PL6 for
system – 13.11.2009
T7 – Delivery Marconi, Nizza, Dante & Spezia for
system – 03.05.2010
T8 – Delivery Lingotto and finish – 03.05.2010

Operations in one year:
Job site alteration
Facility relocation
Diaphragms execution
Station box execution
Site cleaning and preparing for TBM installations
Site cleaning and preparing for TBM installations
TBM assembly

2. Procurement of TBM
Criticality
Short period between notice to award and operation;
Saturated market bearings from eolic request;
High risk of failure of procurement.
Countermeasures
Market investigation about new TBM availability;
Market investigation about used TBM availability;
Risk plan to manage the acquisition.

2. Procurement of TBM
Solution
Used TBM from job site in Paris with contingency plan for refurbishment of machine.
Main works:
1. Bearing inspection and service;
2. Service of cutter-haed;
3. Service of screw conveyor;
4. Change of belt;
5. Cylinder pressures tests
6. Certification of tanks (water and oil)
7. Certification of hyperbaric chamber;
8. Replacement of suctions sealing;
9. Replacement of cables;
10. Replacement of guidance and operation system;
11. Replacement of pressures cells.

• Soil geological conditions;
• Presence of groundwater table;
• Presence of existing buildings with different static conditions;
3. Design Process;
The main risk factors associated to the design phase were:
• Presence of existing buildings with different static conditions;
• Interference with U/G and A/G existing facilities and utilities;
• Environmental constraints;
• Settlements.

The parameters and uncertainties of a mechanized excavation of a tunnel in the middle of a
town require to be accurately studied and monitored.
The soil and above ground conditions, ground water and above-underground services,
buildings and their conditions, are elements which have a great influence in the design and
execution of the project.

The most important actions to be taken during the design and realization phases
were:
• Identification, study and management of the risks (which could be really high);
• Soil and environment investigation;
• Monitoring and connections among the different components.
Actions were:
Design phase
• Continuous analysis of the design using monitoring data from construction
Construction phase
• Monitoring, inquiry and verification of design parameters applied to
construction

The different steps of the process
are:
• Identification of the risks (initial
one);
• Reduction of the initial risk
working on the impact and/or
possibility of occurrence of an
event (i.e. provisional building
event (i.e. provisional building
works, choice of the machinery,
control of the TBM head
pression);
• Management of the residual risk (i.e. monitoring).
The correct interpretation and handling of the above mentioned process cannot completely
eliminate the risk connected to the realization of whatever work, but provides the
instruments necessary to the Client, Designer and Builder to handle the events in a correct
way.

The residual risk, was been managed during the constructive phases by means of the
implementation of an integrated monitoring system to:
• Guarantee the correct flow of information to permit designers to analyse and verify
the hypothesis used to develop the basic design;
• Allows to understand the atypical phenomena giving the information necessary to
solve the problem.
The project defines two parameters
which identify the “attention” and
“alarm” levels.
“alarm” levels.
• Attention level activates a specific
control system in order to reach a more
specific following of the event.
•Alarm level requires the adoption of
the counter-measures specifically
studied for the event.

During the execution phase the main aspects considered were:
• Groundwater;
• Lifting/settlements deriving from the consolidation process;
• Movements deriving from the excavation works;
• Settlements deriving from the TBM mechanized excavation.
GREAT AMOUNT OF
INFORMATIONS
The balance between lack and redundancy of information is necessary to take the correct
actions.
• Little information could determine:
situation where a danger is not consider an emergency situation;
or could not promptly signal its occurrence;
• Too much data could determine a situation of decisional paralysis.

Torino Metro Line 1 : Geology/Geotechnics
The formation interested from the tunnel line is mainly constituted by fluvio-glacial and fluvio-Rissian deposit (Quaternary), of gravel
sand and cobbles in silty matrix. Within this formation there are 4 units identified by specific granulometric characteristics and
different cementation:
• unit 1 – superficial ground
• unit 2 – gravel with sand from loose to slightly cemented
• unit 3 – gravel with sand from weak to medium cemented
• unit 4 - gravel with sand from medium to highly cemented.
The tunnel excavation interested mainly unit 2 and 3. The ground water level varied from tunnel invert up to a maximum height of 7
m measured at crown (Shaft n°6).

4. Public opinion;
The insertion of infrastructure in a
Turin urban environment should
consider that its layout is strictly
connected to the site topography
(highly populated environment) and to
the existing infrastructures and
structures.
Even if they don’t interfere in a direct
Even if they don’t interfere in a direct
way with the tunnel, they could
represent an obstacle to the
construction of stations, ventilation
shafts, access points and/or
emergency accesses. The high
interaction level with the traffic and
the surface activities should be
carefully studied in order to manage
problems with the public opinion.

5. Legislative conditions;
Legislative conditions
Small areas of the construction sites
Environmental requirements
involving a study of the executive
phases, a precise planning of the
procurements and of the
materials evacuation equipment
in order to reach the identification of machineries necessary to minimize the
transmission of the vibrations to the adjacent buildings caused by their transit in
tunnels (wheeled vehicles, discharge belts, mud pumping, etc.)

The main aspects which were been highlighted and analyzed during contract:
1. Consolidation typology and techniques;
2. TBM (Tunnel Boring Machine) typology and features;
3. Environmental monitoring;
4. Structural monitoring.
4. Structural monitoring.

The most important aspect to be considered is
Tender design assumed as method:
- Injections;
- Sheet pile.
Due to the presence of structures near or
under infrastructures or buildings and the
groundwater presence with the aim of
improving the soil features and provisional
support systems necessary during the
excavation phase. Project Hypothesis
The most important aspect to be considered is
the realization of a careful analysis of its
consequences on the building structure and the
existing ones.
For the first ones the major risks are due to:
• Lack of an effective treatment;
• Abnormal pressures;
• Cracks and infiltrations;
• Creep phenomena;
For the second ones the major risks are due to:
• Settlements and/or lifting of near structures;
• Damaging of the buildings;
• Environment pollution.
Project Hypothesis
Real intervention
Turin – Line 1

The choice of the service systems can be influenced by external elements, such as noise
limits, particular buildings and inhabitants, etc.
For example, after the acoustic modeling of the Turin Metro the mortar production system
was changed in order to improve the acoustic comfort of the people resident in the area.
Turin – Line 1 – Mortar Production plant Turin – Line 1 – Final. No plant

5. Environmental requirements;
The environmental requirements are increasingly important in the design process and
construction of infrastructure in urban areas.
Environmental Monitoring target:
• Limitation of the construction activities impact
• Compliance with the local environmental regulations
• Immediate management of unforecast impacts by means of effective
communication and specialized competences
communication and specialized competences
These aims can be achieved by:
• Assessment of the environmental conditions before construction (Ante Operam
Monitoring)
•Evaluation and monitoring of the environmental quality during construction
(Monitoring During Construction)
• Correlation between the environment changes and the construction site
progress
• Immediate intervention when environmentally critical thresholds are exceeded

The study and intervention areas can be divided into 3 groups:
1. Environmental monitoring:
a) Atmosphere
b) Noise;
c) Vibrations.
2. Management of excavation earth and rocks;
3. Green management.
For the realization on the interventions in the Turin and Rome Metros
have been employed the following methodologies:
a) Atmosphere monitoring methodologies
Measurement of total inhalable dust;
Measurement of dust lay;
NO2 and C6H6 measurement.
b) Noise monitoring methodologies:
24 hours measurements;
7 days measurements;
Short period measurements in a living environment.
c) Vibration monitoring methodologies:
Short period measurements;
Long period measurements.

Monitoring campaigns
Comparison of the results obtained with the threshold limits
Threshold limits exceeded Threshold limits met
Open af an anomaly:
Cleaning of pavements where
there is the
vehicles transit;
maintenance of
clearing brushes, etc.
Optimization of pumps acoustic
insulation, etc.
Open af an anomaly:
Analysis of the possible causes which produced the criticality
and prompt execution of the mitigation interventions to solve
and/or control the problems occurred
Examples of mitigation
intervention realized

As specified before,
also in this case it is
extremely important
the interaction
project-construction-
monitoring-project,
both for the
management of the
anomalies and for the
implementation of the
threshold limits for
threshold limits for
works execution.
In the specific Turin case, the ongoing atmosphere monitoring campaigns are realized on 28
receptors with:
• 35 measurements of total PM10 inhalable dust
• 58 measurements of dust lay
• 40 NO2 and C6H6 measurements

In the following chart have
been highlighted the reference
and results with the trends and
the PM10 limits exceeding.
been highlighted the results
with the trends and the limits
exceeding of sediment
airborne dust.

with the trends and the
benzene limits exceeding.
with the trends and the NO2
limits exceeding.

The noise monitoring campaigns are carried out on 20 receptors with:
• 39 measurements semi-fixed workstations;
• 41 measurements fixed workstations;
• 15 short period measurements, living environment.
In addition, to guarantee 24 hours/day – 7 days/week working conditions has been
developed an integrative monitoring system to define and control the limits
The working and management
flow can be represented by the
interaction among the different
subjects involved:
Contractor
Asks for the issue of an
Authorization for a specifica
temporary activity
•24 spot
monitored
Authorized
Monitoring:
Possible
definition of a
continuous
monitoring
activity or “ad
hoc” spot
measurements
as control of the
most impacting
activities
subjects involved:
The Designer and Contractor
require the approval of the
project acoustic impact; the
control Authority defines the
evaluation parameters and
grants the authorization; then
the Designer and Contractor
monitor the acoustic impact
when the works are in progress,
mainly during the execution of
the activities which have the
biggest acoustic impact.
Municipality
temporary activity
Gives authorizations and
fixes the time thresholds
limits, prescriptions to
limit the noise
emissions.
Authority
Gives its technical-
scientific support for
the evalutation of the
issue of the
authorization
monitored
•2 receptors
monitored with
fixed
monitored
stations
•3 weekly
monitored
receptors

The vibration monitoring campaigns are in progress and realized on 14 receptors:
• 37 short period measurements
• 10 long period measurements (24 hours)

The Excavation Material management is subject to both national and local regulations.
Metro excavation operations normally produce two types of materials:
• Treated soils
• Untreated soils
Turin Metro project included a plan of re-use of the excavation soils following the above
classification, i.e.:
• Soils and rocks from Stations, Wells, Surface excavations and walls are continuously
• Soils and rocks from Stations, Wells, Surface excavations and walls are continuously
assessed for re-use in quarries
• Soils and rocks from excavation with TBM are temporarily disposed to be assessed and
subsequently re-used for backfilling, embankments and other compatible uses.

TBM
Transport belt to
TBM starting site
Wagons and fixed
crane
Surface
temporary depot
Load and
transport
temporary area
temporary depot
Discharge and
creation of piles
in the
operational lots
Trasport to final
destination

The temporary area is divided into operational lots, which are gradually filled to
guarantee the traceability of the excavated material.
The characterization is divided into the following phases:
• During the excavation phase at the excavation TBM head;
• At the temporary depot in every operation lot;
to guarantee that each sample (which have been previously taken and analysed
during and after the decay phase) contains concentrations of elements in
accordance to the parameters analysed are lower than the concentration limits
provided by the legislation.

Management of the green elements.
The ante-operam activities are:
• Census of all the trees which could interfere with the works;
• Evaluation, for each tree, of the interference percentage;
• Evaluation of the possibility of maintaining the trees
(properly protected by crashes) in the area;
• Evaluation of the necessity of removing the trees;
• Evaluation of the necessity of removing the trees;
• Definition of the removal intervention typology (cutting
down or transplanting) in accordance with:
species
dimension
phytopathological status
• Evaluation of the possibility of relocating the trees in original
site, at the end of the works.

The transplanting has been realized by special equipments in order
to safeguard the trees radical planting and guarantee a correct
rooting in the new site.

TBM Selection – Application field.

The areas of TBM employment following the soil conditions can be represented as follows:
The main requirements a TBM should have to work in a urban environment can be connected to:
• Workers safety;
• Realization of the excavation process, including:
materials provision (inside the TBM);
material discharge;
easy maintenance of the TBM head.
• Interaction with monitoring parameters;
• Availability of equipments necessary to control the excavation head pressure;
• Equipments to realize tests and surveys inwards;
• Availability to realize additional treatments inwards;
• Assembling, maintenance and disassembling flexibility;
• Driving flexibility.

Soil correction.

Selected TBM
TBM (EPB) Marca e modello
Herrenknecht
Mod. S-415
Tratte e lotti T2 - Lotto 2
Diametro di scavo [m] 7,750
Potenza [kW] 2000
Velocità di rotazione [rpm] 0,0 - 3,0
Spinta [kN] 55.750
Coppia [kNm] 14.648
Coppia [kNm] 14.648
Lunghezza scudo [m] 8,30
Lunghezza back-up [m] 80
L conci [m] 1,40
Sp conci [m] 0,30
Diametro int [m] 6,88
Copertura tipica [m] 12
Copertura max [m] 20
L tratta [km] 3,1
1. Fronte di attacco
2. Testa di scavo
3. Camera di scavo
4. Parete di pressione
5. Cilindro di spinta
6. Coclea
7. Conci
8. Coda

Previous projects:
France – Tolosa 2003 -2005
Metro project [5.600m]
France – Parigi 2006 - 2007
Water reservoir [1.800m]

Main works:
1. Bearing inspection and service;
2. Service of cutter-haed;
3. Service of screw conveyor;
4. Change of belt;
5. Cylinder pressures tests
6. Certification of tanks (water and oil)
8. Replacement of suctions sealing;
9. Replacement of cables;
10.Replacement of guidance and operation
system;
11.Replacement of pressures cells.

Cutter-head refurbishement

Cutter-head as dressed in Marconi

Cutter-head as dressed in Nizza

Segmental lining
Diametro esterno De = 7.48m
Diametro interno Di = 6.88m
Spessore s = 0.30m
Raggio di progetto R = 261.8m
Lunghezza media L = 1400mm
Lunghezza minima Lmin = 1380mm
Lunghezza massima Lmax = 1420mm
Numero di conci n = 6
Volume anello Va = 9.4725m3
Volume anello Va = 9.4725m3

TBM Site installation

Material and segments feeding

The correct choice of the TBM is the first step to
manage the excavation.
Then it is necessary to identify and define the
other equipments to be used, depending of job
site conditions such as:
• Trains or Dumper
• Mortar or double-component systems
• Mortar or double-component systems
• Purification systems – Water treatment plants
• Compressors
• Slurry Shield (SS) or Earth Pressure Balance
(EPB) TBM
• Service crane
• Segment storage area

Much removal

Ancillaries Plants
Elettroventilatore da 135 kW
Torre di raffreddamento: 4 pompe da 11 kW + 1 elettroventilatore da 7,5 kW
Carro ponte per sollevamento in superficie materiale di smarino, composto da 2 motori per
l’argano di sollevamento da 135 kW, 4 motori di traslazione da 7,5 kW, 2 motori di
traslazione da 4 kW
traslazione da 4 kW
Gru Potain 310 B
Impianto di depurazione acqua (10 mc/h)
Argano raccoglitore nastro
Cabina elettrica di trasformazione 22.000/20.000 V
GE per emergenza da 400 kW
Mescolatore con invio malta in galleria

Assembly

Steel rings

Thrust Frame

The correct project and development of the soil stability system is extremely important.
To guarantee the pressure control at the head of the front and to allow the formation of a
material easy to be extracted from the screw conveyor it is necessary to put conditioning
agents in the excavated soil, such as bentonite, foaming agents, polymers and thin material.
In our case, we wear the TBM with a separate circuit of emergency injection of bentonite to
avoid loosing pressure and settlements.

The most important requirement for our job was the environment protection, in order to
preserve the soil, buildings, utilities and already existing structures.
Features in order to choose the correct excavation and TBM typology:
• Settlements;
• Interferences;
• Depot of demolition materials, with particular attention to their feature and to pollutant
agents;
• Interface of the external monitoring systems with the parameters of TBM control;
• Availability of areas to assemble, launch and extract the TBM.
Turin – Line 1 – Head of TBM

Soil Conditioning

Mechanized excavation : Basic principles
The Earth Pressure Balanced (EPB) tunnelling method owns it’s name
from the way the front face of the TBM is supported during excavation,
using earth pressure. The principles of the EPB-tunnelling method can
described as follows (Kanayasu, Yamamoto and Kitahara, 1995):
• The soil is excavated by rotating cutter heads;
• The excavated soil is mechanically agitated and fills the face and an
excavation chamber.;
• Using the thrust of the shield machine, by means of hydraulic jacks,
the excavated soil is pressurized to stabilize the excavation front (force
equilibrium);
• Control of the soil pressure in the chamber is done by adjusting the
amount of soil discharged through the screw conveyor or other soil
removal devices and the amount of soil excavated to counterbalance
earth and groundwater pressure (volume equilibrium);
• The excavated soil in the chamber and the screw conveyors work as
a water seal.
The earth pressure support method is generally used in cohesive soils,
enabling it to be used as a supporting medium itself, with the use of
conditioning materials if necessary.
A

Support pressure – Calculation Methods used on Metrotorino
METHOD OF LECA & DORMIEUX (1990)
This method is based on the upper and lower limit theorems with a 3D-modelling. The
upper(+) and lower (-) limit solutions are obtained by means of a cinematic and a static
method, respectively, giving thus an optimistic and a pessimistic estimation of the face-
METHOD OF JANCSECZ & STEINER (1994)
According to the model of Horn (1961), the three-dimensional failure scheme consists
of a soil wedge (lower part) and a soil silo (upper part). The vertical pressure resulting
from the silo and acting on the soil wedge is calculated according to Terzaghi’s
solution.
A three-dimensional earth pressure coefficient ka3 is defined as:
ka3 = (sinβ · cos · – cos2β · tanφ – K · α · cosβ · tanφ/1.5)/(sinβ · cosβ + sin2β ·
tanφ)
where:
K ≈ [1 – sinφ + tan2(45 + φ/2)]/2;
α = (1 + 3 · t/D)/(1 + 2 · t/D).
method, respectively, giving thus an optimistic and a pessimistic estimation of the face-
support pressure. In the case of dry condition, the face support pressure σT is (Ribacchi
1994):
σT = – c’ · ctgϕ’ + Qγ · γ · D/2 + Qs · (σs + c’ · ctgϕ’)
where Qγ, Qs = non dimensional factors (from normograms), function of H/a and ϕ’; a
= radius of the tunnel; H = thickness of the ground above the tunnel axis.
METHOD OF ANOGNOSTOU & KOVARI (1996)
This method, later referred to as A-K method, is based on the silo theory (Janssen 1895)
and to the three-dimensional model of sliding mechanism proposed by Horn (1961).
The analysis is performed in drained condition, and a difference between the stabilizing
water pressure and effective pressure in the plenum of an EPBS is presented. If there is
a difference between the water pressure in the plenum and that in the ground,
destabilizing seepage forces occur and a higher effective pressure is required at the face.
However, accepting this flow, the total stabilizing pressure is lower than the pressure
required in the case of an imposed hydrogeological balance. The effective stabilizing
pressure (σ’) :
σ’ = F0 · γ’ · D – F1 · c’ + F2 · γ’ · ∆h – F3 · c’ · ∆h/D
where F0,F1,F2,F3 are non-dimensional factors derived from normograms, which are
function of H/D and ϕ’.

Past experiences in Japan (from Kanayasu)
METHOD OF DIN 4085 (GERMAN STANDARD)
In this model, three-dimensional active earth pressure is calculated according to DIN 4085, which is based on the failure
mechanism theory of Piaskowski & Kowalewski. The method divides the tunnel face into multiple horizontal strips.
The three-dimensional active earth pressure acting on each strip is calculated with the two-dimensional active earth
pressure method, adjusted by reduction factors. These factors are calculated depending upon the ratio of depth of the
layer to tunnel diameter.
To ensure stability of the tunnel face, it is necessary to counterbalance the total force of active earth and water pressure.
These forces are multiplied separately with safety factors as per the concept of partial factor of safety
Psupport= η a E a + η w W
Where, η a and η w are partial factors of safety for active earth pressure (Ea) and water pressure (W) respectively.
Support pressure – Calculation Methods used on Metrotorino
MetroTorino [kPa]20'
++= wvakP σσ

70
80
90
100
110
120
Pressure[kPa]
Support pressure - Calculations using different methods
Spinta attiva Ka
Spinta a riposo
Ko
DIN 4085
10
20
30
40
50
60
1097 1147 1197 1247 1297
Pressure[kPa]
Chainage [m]
Anagnostou &
Kovari
Leca-Dormieux
Normativa
olandese COB
Jancsecz &
Steiner
PL2
SHAFT
NIZZA
STATION

EPB – SUPPORT PRESSURE
Warning Pressure in working
chamber
Attention Po = 0.9 Pd Po = 1.2 Pd
Alarm Po = 0.8 Pd Po = 1.3 Pd

PENETRATION RATE [mm/min]
PRESSURE SENSORS [Bar]
Excavation parameters control
The parameters, to be verified via the sensors and sensing equipment, are:
• Face-support pressure
• Pressure and volume of the backfill grout of the annular void
• Weight of the extracted material
EXCAVATION PHASE
OPERATIONS – BUILDING RING
SCREW CONVEYOR RATE [rpm]

EPB –TBM OPERATION MODE

END EXCAVATION PHASE
END EXCAVATION PHASE
PRESSURIZED AIR/FOAM INFLOW
SCREW CONVEYOR STOPPED
PRESSURE INCREASE

Definition of normal and anomalous conditions
Normal excavating conditions are considered all those conditions, whose EPBS excavation characteristic parameters fall within the “attention”
thresholds
Anomalous conditions are associated with:
• Water inflows under pressure through the screw conveyor.
• Sudden oscillations of the torque of the cutterhead.
• Blockage of the cutterhead.
• Anomalous pressure values in the excavation chamber.
• Sudden and significant variations of the muck density in the excavation chamber.
• Weight of the muck extracted by the screw conveyor surpassing the “attention” threshold.
• Insufficient pressure and/or volume of the grout injected behind the lining.
Pressure management in the work chamber
Pressure management in the work chamber
Sudden variations of the face-support pressure could be the warning signals resulting from torque
increases or head blockages.
In case the pressure increases:
•The head rotating speed is reduced to <1 rpm.
•The thrust is reduced so that penetration rate, Vp, is <10 mm/min.
•The foam flow is increased by 20%,without increasing the muck discharge from the screw.
In case the pressure diminishes:
•Bentonite is injected to re-establish the design support pressure.
•If pressure still does not increase, excavation is stopped and the screw gate is closed.
•Bentonite and polymer injection is continued until the designed support-pressure is achieved.

Weight Management
Special method statement,
additional investigation

The tunnels have inner diameter of 6.8mt and is lined with pre-cast 30 cm thick segments in reinforced concrete,
connected by EPDM gaskets to insure water tight conditions. Even withrather small curves and consequent assembly
offsets of the segment ring, there is no water passage within the tunnel.
Each 1.4 m long ring consists of 5 “normal” elements plus one “key” element that enables the closure of the ring, a
“universal” lock that permits to adapt the ring to any kind of radius, from the minimum to the linear one, by a simple
rotation of every ring compared to the previous one along the tunnel axis at a given angle.
The injection of mortar behind the segments, performed immediately at the beginning of the excavation procedures,
ensures the reduction of superficial collapse and the correct confinement/bedding of the lining.
The RING

Segment Design Steps
Generally, design steps for TBM tunnels could be as follows (ITA,2000):
Step 1: Define geometric parameters
Alignment, excavation diameter, lining diameter, lining thickness, width of ring,
segment system, joint connections
Step 2: Determine geotechnical data
Shear strength of soil, deformation modulus, earth pressure coefficient
Step 3: Select critical sections
Influence of overburden, surcharge, groundwater, adjacent structures
Step 4: Determine mechanical data of TBM
Confinement pressure, overcut, shield tail conicality, TBM length, total thrust
pressure, number of thrusts, number of pads, pad dimensions, grouting
pressure, space for installation. All these structural parameters associated
with TBM characteristics may have potential impact on ring stress analysis.
Step 5: Define material properties
Concrete: compressive strength, modulus of elasticity
Concrete: compressive strength, modulus of elasticity
Reinforcement: type, tensile strength
Gasket: type, dimensions, allowable gap, elastic capacity
Step 6: Design loads
Soil pressure, water pressure, construction loads etc.
Step 7: Design models
Empirical model, analytical model, numerical model
Step 8: Computational results
Response: axial force, moment, shear
Deformation: deflection
Detailing: reinforcement, joints, groove

Loading Conditions
The tunnel lining behind the TBM must be capable of
withstanding all loads/actions and combined actions
without deforming, especially during ring erection and
advance.
Single-shell reinforced concrete segmental rings behind
the TBM, can be designed to fulfill those demands.
Secondary lining can also be constructed with cast-in-
place concrete as a structural member of the segmental
lining.
There are many loading cases for the segmental lining of
tunnels driven by TBMs.
tunnels driven by TBMs.
The following loads shall normally be considered in
designing the lining of the shield tunnel (JSCE, 1996):
(1) Vertical and horizontal earth pressure
(2) Water pressure
(3) Dead weight
(4) Effects of surcharge
(5) Soil reaction
(6) Internal loads
(7) Construction loads
(8) Effects of earthquakes
(9) Effects of two or more shield tunnels construction
(10) Effects of working in the vicinity
(11) Effects of ground subsidence
(12) Others
Various combinations of the loads can be considered
according to the purpose of the tunnel usage.

Geostatical Loads
This load case analyses the load effects on lining segments and ground. For MetroTorino we employed FLAC to predict axial load and
bending

Thrust Jacking Loading
The functions of the linings during tunnel construction are to sustain jack thrust
for advancing a shield machine and to withstand the back-fill grouting
pressure. The linings have also the function as a tunnel lining structure
immediately after the shield is advanced.
Thrust force of shield jacks is a temporary load which acts on the segment as
a reaction force against it while advancement the shield machine and is the
most influential load to the segment among the construction loads. Several
verifications must be done for the jacking load effects on the segment, such as
contact pressure, bursting forces in the radial direction, and bursting forces in
the circumferential direction.

Grouting Loads
Primary grouting pressure applied to fill up the tail void behind the TBM is
believed to govern both deformations and internal lining forces, as well as
affect surface settlements. The grouting pressure acting on the outer surface
(extrados) when the ring leaves the shield. For normal conditions, when a
highly flowable mortar is used, the grouting pressure can be calculated
constant around the ring. The annular grouting of the ring, with a grouting
pressure minimum one bar (1 bar) higher than the surrounding water
pressure, prestresses the ring and the enclosing ground.
Secondary grouting pressure is an extending regular grout pressure. These
transient type loads result from a localized increase in grouting pressure
("local pumping thrust") directly behind the segment grouting holes.

Storage Loads
After mould stripping, segments are set down and stacked on
supports. Timber blocks are usually placed between segments
taking care that they are aligned with the supports. Storage and
handling (e.g. turning, packing and then loading-out operations,
supply to the workface…) influence the bending moment.

Handling Loads
During erection, the lining is subjected to a number of loads
such as: forces resulting from segments overhanging during
ring assembly; possible bumping impact loads; loads applied
by the assembly systems retained (bolts, anchor bolts or
plugs) it is necessary to consider the increasing in the mass
forces due to dynamic effects.

Trailer Loading
Trailer chassis and other service loads can be applied on lining, including
main bearing loads, divided by number of wheels .The loads induced by the
trailer and by any fixations in the segments normally do not influence the
Possible future excavations next to structures
Possible future buildings must be considered in the analysis, assuming
some restricitions. As an example (zone 4B):
•Vertical restrictions - Excavations shall not exceed a total depth of 8 m.
•Lateral restrictions - No future excavations shall take place within an area
of 5 m above the tunnel crown and 17 m on either side of the tunnel centre
line.
trailer and by any fixations in the segments normally do not influence the
reinforcement. During discussions with TBM manufacturer, it is necessary
to state whether "Main Bearing Load" will be included in this type of analysis
or not.
Fire load
Concrete tunnels are vulnerable to elevated temperatures caused by fire.
Tests have shown that when the temperature of the reinforcement reaches
300˚C, the bond between the rebar and concrete will be significantly
reduced, leading to irreparable sagging and possible collapse of the total
structure. Moreover, when concrete is exposed to fire temperatures as
experienced in tunnels, concrete spalling often occurs. Tunnel cross-sections
must be analyzed to consider fire loading.

Settlement and Volume loss

In a properly supported non-TBM tunnel, 70-80% of total surface settlement is due
to deformations ahead of tunnel face. In a shield-driven excavation, the fraction
varies significantly (<< 70%) depending on the method. As an example, until a
recent date, the following distribution of settlements to the surface was observed:
- 10 to 20 % caused by the face;
- 40 to 50 % caused by the void along the shield;
-30 to 50 % caused at the end of the tail seal.
The net volume of the surface settlement trough will be approximately equal to the
volume loss at the tunnel in most ground conditions. If the ground response is at
constant volume (i.e. undrained), the relationship will be exact. The hypothesis will
be checked especially if the ground is clayish and the overburden is thin.
The magnitude of the volume loss VL depends on many different factors:
soil type
tunnelling method
rate of tunnel advance
tunnel size
Settlement and Volume loss
tunnel size
form of temporary and primary support
Before the magnitude of ground movements can be predicted it is necessary to
estimate the expected ground loss. This estimate will be based on case history data
and should include an engineering appraisal that takes into account the proposed
tunnelling method and site conditions.

Settlements calculation : Numerical method
Paratie con solettone copertura e piano atrio di contrasto
-2.0
-1.5
-1.0
-0.5
0.0
141516171819202122232425262728
Distanza fondazioni-paratia [m]
Cedimento[mm]

Settlements calculation : Empirical method
Empirical methods are used to assess the settlements using
formulas that are based on empirical relations between available
data. This data has been collected and assessed by a lot of
researchers and for a lot of different projects.
Peck (1969) was the first to propose that the surface
settlement profile could be represented by a Gaussian
distribution curve.
In Turin Metro volume loss was about 0.3-0.5%

-3.7
Volume perso [%] 1
Diametro Galleria [m] 7.90
Copertura [m] 10 0.00
Parametro K 0.375 -0.85
Distanza tra gli assi [m] 0 0.000309
-
Ascissa SX edificio [m] -24.4 0.036551
Ascissa DX edificio [m] -9.4 0.00
Altezza [m] 7.1
Rapporto E/G 12.5 0.046273
0.000000
0.050410
0.00
0.050410
1
Epsilon terreno Hogging [%]
DATI DI INPUT
Cedimento massimo singola canna [cm]
OUTPUT
Interferenza n° 1000
Cedimento vertice SX [cm]
Cedimento vertice DX[cm]
Rapporto δ/L zona di Hogging
Rapporto δ/L zona di Sagging
CATEGORIA DI DANNO
Epsilon terreno Sagging [%]
Epsilon flessionale Hogging [%]
Epsilon flessionale Sagging [%]
EPSILON MASSIMA
Epsilon Tagliante Hogging [%]
Epsilon Tagliante Sagging [%]
Cedimenti [cm]
Settlements calculation : Building damage assessment
EPS MAX flex hog 0.0007816
EPS MAX flex sag 0.0016316
EPS MAX tag hog 0.0006761
EPS MAX tag sag 0.0014412
Deformazioni Epsilon [%]
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
-20 -15 -10 -5 0 5 10 15 20
Canna sx
Canna dx
Totale
Cedimenti [cm]
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
-20 -15 -10 -5 0 5 10 15 20
Canna sx
Canna dx
Totale

Soil improvement solutions have been implemented where the
assessments indicate potential risk of damage to the pre-existing
structures. Such interventions include improving the properties of the
ground and mitigating the deforming effects induced by tunnelling by
means of low-pressure cement injection grouting. A consolidated slab
is created above the tunnel section in order to avoid any localized
instability from developing around it.
Different grouting geometry have been defined, based on relative
position between the tunnel and pre-existing structures, as well as
site accessibility and surface site areas use.
The project includes full-face cement grouting in the areas adjacent
to the stations where the TBM will enter into or exit from the stations:
the diaphragm walls in these particular areas will be partially
demolished to let the TBMs in and out. In accordance with the
environmental conditions, the drilling and grouting operations were
environmental conditions, the drilling and grouting operations were
done from the surface and/or from in service shafts and tunnels.

MONITORING
• STRUCTURAL MONITORING:
– TENSION (STRAIN GAUGES, LOAD CELLS, etc.)
– DEFORMATION, SETTLEMENT (INCLINOMETERS,
OPTICAL TARGET, etc.)
• BUILDING MONITORING:
– BUILDINGS DISPLACEMENTS (TOPOGRAPHIC
SURVEYING, ELECTRONIC LEVEL, CONTINUOUS
MONITORING, CLINOMETER, etc.)
– CRACK GROWTH (CRACK MONITOR)
– VIBRATION (VIBROMETER)
BE: Strain gauge
CTC: Optical target
IN: Inclinometer

Interferences with subservices
Example: existing sanitary sewer

Interferences with subservices
Example: rain water sewer

Torino metro urban project should take account of a multidisciplinary approach that
considers all the processes of the entire lifecycle and performance of the works.
The integrated methodological approach, implemented in the execution of projects and
works of construction into urban areas, must necessarily involve the adoption of a process of
continual revision of the initial assumptions of the design, through the continuous
analysis of monitoring data for proper risk management.

Multidisciplinary analysis;
Design review;
Management of environmental issues;
Management of public opinion;
are elements that are becoming increasingly important in the execution of a project
are elements that are becoming increasingly important in the execution of a project
and the subsequent works.
This approach addresses the proper way to proceed towards subjects who are able
to manage not only the design phase, but also the construction phase
to ensure consistency in approach, construction and commitment during the
whole lifecycle of the project.

THANK YOU
THANK YOU

Torino Metro Experience

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