Difficult Ground Solutions: A Methodology for Enhanced TBM Performance in Challenging Conditions Introduction: Difficult Ground Solutions The

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Ariel Bennett
6 years ago
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2 Difficult Ground Solutions: A Methodology for Enhanced TBM Performance in Challenging Conditions Introduction: Difficult Ground Solutions The Techniques: Strategies for Difficult Ground Solutions Water Inflows Face Collapse Squeezing Ground TBM Project Designs for Difficult Ground Delaware Aqueduct Repair Gerede Water Tunnel Conclusions

3 What is Difficult Ground? Particular Geological Features Fault zones Rock bursting Water inflows Hard, abrasive rock Squeezing ground Collapsing ground Fractured rock Mixed face conditions High water pressures Cobbles and boulders

Difficult Ground Solutions (DGS): When does it Apply? Difficult Ground Solutions (DGS) are a suite of options for non pressurized or pressurized, shielded TBMs in hard rock and mixed ground.

4 Difficult Ground Solutions (DGS): When does it Apply? Difficult Ground Solutions (DGS) are a suite of options for non pressurized or pressurized, shielded TBMs in hard rock and mixed ground. Ground support features can also be applied to Open Gripper TBM s Features are customized for known geologic conditions including squeezing ground, fault zones, water inflows, and collapsing ground

5 Difficult Ground Solutions: Benefits Reduces risk to contractors and owners when a challenge is encountered Like buying risk insurance: A small initial investment can pay off if a difficult feature is encountered VIDEO: Gerede Water Tunnel, Turkey

6 Strategies for Water Inflows: Detection Probe drilling in advance of face Multiple probe holes in faulted areas Read & interpret the bore data (Measurement while Drilling Systems) Probe drilling in advance of face

7 Strategies for Water Inflows: Preventative Machine Design Water inflow prevention at the muck chute Sealable pressure bulkhead Sealable shields

Strategies for Face Collapse: Detection Collapse Detection Cylinders to identify ground when collapsed onto the front shield Temposonic cylinder to measure distance from

8 Strategies for Face Collapse: Detection Collapse Detection Cylinders to identify ground when collapsed onto the front shield Temposonic cylinder to measure distance from shield to ground Cameras to provide visual inspection of the cut face Allows understanding of ground stability Uses pre positioned ports that pass through the back of the cutterhead

Strategies for Face Collapse: Detection and Mitigation Probe/Grout drilling Similar to when water inflows are suspected/detected, it is necessary to

9 Strategies for Face Collapse: Detection and Mitigation Probe/Grout drilling Similar to when water inflows are suspected/detected, it is necessary to detect and grout off zones of concern in collapsing ground Enhanced probe drilling capabilities including ability to grout directly through the face are key

10 Strategies for Face Collapse: Multi Speed Gearboxes Provides High Torque/Low RPM mode to get through fault zones Low Torque/High RPM for rock conditions Breakout thrust/torque options Cutterhead Torque (knm) Low Speed Exceptional Low Speed High Speed Exceptional High Speed Cutterhead Speed (RPM)

11 Strategies for Squeezing Ground: Shield Design Shorter shield design Stepped/tapered shields Overcut capability Convergence measuring system Peripheral shield lubrication High Emergency Thrust and or Super High Breakout Thrust

12 Strategies for Squeezing Ground: Ground Treatment Wands pushed into face and chemical additive (Polyurethane) is pumped into the wands to consolidate the face Forepoling from shield

difficult ground Additional hydraulic rams are used to increase

13 Strategies for Squeezing Ground: Super Thrust Purpose When needed additional thrust force can be generated to move the TBM in difficult ground Additional hydraulic rams are used to increase the total available machine thrust to break the TBM free High Pressure Jack

pressure (static) Multiple Drilling Units installed Periphery and face drilling

14 TBM Design: Delaware Aqueduct Repair Machine design considerations: Hard Abrasive rock Mpa (Granite Gneiss ) Ability to cope with 35bar water pressure (static) Multiple Drilling Units installed Periphery and face drilling required Closable and sealable muck ring and shield system High torque cutterhead Drive System

15 TBM Design: Delaware Aqueduct Repair Multiple drill holes: Need fast, accurate drilling at long distances 60 to 100 m ahead of the TBM Down the hole Hammers: Ideal for drilling multiple holes for water cut off Straighter drilling compared to top hammer drilling

TBM Design: Delaware Aqueduct Repair Two speed gearbox: Operational torque Exceptional torque Cutterhead Torque [knm] 10000 9000 8000 7000 6000 5000 4000 3000

16 TBM Design: Delaware Aqueduct Repair Two speed gearbox: Operational torque Exceptional torque Cutterhead Torque [knm] VFD Torque Curve Cutterhead Speed [rpm] Operational Torque Exceptional Torque

17 TBM Design: Gerede Water Tunnel 5.60 m diameter Crossover (XRE) TBM with Single Shield and EPB TBM characteristics Single direction rock cutterhead High strength shield with closed bulkhead to resist water & mud inflows Bottom screw conveyor Dual ratio transmission for high torque capability High pressure articulation and tail seals High thrust capacity Multi position probe drilling

TBM Design: Gerede Water Tunnel TBM can statically hold up to 20 bar pressure in event of water inflow Extensive sealing system in place Sealing around main bearing, articulation

18 TBM Design: Gerede Water Tunnel TBM can statically hold up to 20 bar pressure in event of water inflow Extensive sealing system in place Sealing around main bearing, articulation joint, gripper and stabilizer shoes Between each seal, grease ensures constant pressure Pressure sensor to detect water and continually grease seals HP Articulation Seals 4 Row Tail Seals

19 TBM Design: Gerede Water Tunnel Sealing system to seal itself off so TBM can continue boring through fault zones Replaceable wear plates to protect against highly abrasive rock Removable sectional casings that can be replaced if needed

front of machine In emergencies, the drill can pull back behind the tail shield at an angle of 16, so it can drill behind

20 TBM Design: Gerede Water Tunnel Necessary to detect and grout off zones of concern TBM has twelve Ø100 mm sealed ports angled at 7, equally spaced around the rear shield and ten Ø100 mm ports through the forward shield Six hatches built into front of machine In emergencies, the drill can pull back behind the tail shield at an angle of 16, so it can drill behind the shields and into the segment lining Probe drilling through a port in the machine shield Probe drilling behind the tail shield

21 TBM Design: Gerede Water Tunnel Stepped shield design Peripheral shield lubrication View of stepped shields (left) and peripheral shield lubrication port (above)

22 Difficult Ground Solutions: Takeaway Points The features of Difficult Ground Solutions (DGS) provide accurate ground investigation, particularly on shielded TBMs DGS is well suited to long tunnels and high cover tunnels in mountainous areas DGS features should be built into the TBM in case of adverse conditions, rather than being added in the tunnel. Contractors must work with the equipment manufacturer from the beginning to develop a solution The efficacy of DGS is there to assist when it is obvious a detailed geological survey and report cannot be economically provided

23 Questions? Sydney Metro

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