TORINO UNMANNED SUBWAYCIVIL WORKSIng. Giorgio FantauzziProject LeaderTurin, 12 July 2010
TORINO SUBWAY 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 circular tunnel contains the double track line has been chosen. The tunnel was bored by TBM.
TORINO SUBWAY LINE 1 : CIVIL WORKS 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 Shafts 5 aeration shaft, built using micropiles 3
TORINO SUBWAY LINE 1 : GEOLOGY / GEOTECHNICSThe formation interested from the tunnel line is mainly constituted by fluvio-glacial and fluvio-Rissian deposit (Quaternary), of gravelsand and cobbles in silty matrix. Within this formation there are 4 units identified by specific granulometric characteristics anddifferent 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 7m measured at crown (Shaft n°6).
TORINO SUBWAY LINE 1MAJOR PROBLEMS:• Interferences with utilities and facilities;• Presence of peoples opposed to the project;• Interferences with existing structures;• Surveys to remove archaeological and weaponsfrom 2nd War;• Traffic management near work sites,interferences with commercial activities;• Public opinion;• High groundwater level. 5
TORINO SUBWAY LINE 1 : FIRST OPERATIONSJob site alterationFacility relocationDiaphragms executionStation box executionSite cleaning and preparing for TBMTBM assembly
TORINO SUBWAY LINE 1 Work site Transportations 7
TORINO SUBWAY LINE 1 Utility relocationTecnological wires:- Electric- Telephonic - Gas pipe - Acqueducts - Sewer - Parking - Monuments - Other 8
TORINO SUBWAY LINE 1 : STATION GEOMETRY• Station dimensions 55x20m;• Station deep from 20 to 25m;• Two entrances and one lift for each station; 9
TORINO SUBWAY LINE 1 – THE EPB MACHINE 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
TORINO SUBWAY LINE 1 – THE RING 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.
TORINO SUBWAY LINE 1 – THE CUT AND COVERMETHODCONSTRUCTION PHASES 12
TORINO SUBWAY LINE 1MANAGEMENT OF THE GREEN ELEMENTSThe 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;• Definition of the removal intervention typology (cuttingdown or transplanting) in accordance with: species dimension phytopathological status• Evaluation of the possibility of relocating the trees in originalsite, at the end of the works.
TORINO SUBWAY LINE 1MANAGEMENT OF THE GREEN ELEMENTS 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.
TORINO SUBWAY LINE 1 – SOIL IMPROVEMENT To avoid water inflow Break In TBM Break Out TBM Bottom groutingTo reduce settlements Lateral shield Full improvement at crown 44
TORINO SUBWAY LINE 1 – SOIL IMPROVEMENT 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 done from the surface and/or from in service shafts and tunnels.
TORINO SUBWAY LINE 1 – ENVIRONEMENTALMONITORING NOISE 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. VIBRATION The vibration monitoring campaigns are in progress and realized on 14 receptors: • 37 short period measurements • 10 long period measurements (24 hours) AIR In the following chart have been highlighted the reference and results with the trends and the PM10 limits exceeding. 46
TORINO SUBWAY LINE 1 – STRUCTURAL MONITORING To reduce the residual risk we defined trigger levels for displacement/rotations on structures and surrouding buildings TRIGGER LEVELS • Attention: increase the frequency of monitoring data to understand the real behaviour •Alarm: apply counter-measures to solve the problems 47
TORINO SUBWAY LINE 1 – STRUCTURAL MONITORING 48
TORINO SUBWAY LINE 1 – STRUCTURAL MONITORINGAutomatic monitoring withelectrolevels : the distortionsmeasured during the excavationphase was less than theestablished trigger levels 49
TORINO SUBWAY LINE 1 – CONCLUSION OF WORK START: 08.01.2007 Finishing date (CONTRACTUAL) : 03.05.2010 Finishing date (REAL) : 03.02.2010 TECNIMONT finished the civil works two months before the foreseen contractual date 50
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