H A R D R O C K T B M D E S I G N F E AT U R E S F O R D I F F I C U LT G R O U N D C O N D I T I O N S. Tyler Sandell The Robbins Company

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1 RISK MANAGEMENT: H A R D R O C K T B M D E S I G N F E AT U R E S F O R D I F F I C U LT G R O U N D C O N D I T I O N S Tyler Sandell The Robbins Company

2 PRESENTATION OUTLINE RISK MANAGEMENT IN DIFFICULT GROUND OVERVIEW Introduction Risk Management: Identify Assess and Monitor Response Taking Control Conclusions Q & A

3 AN OUNCE OF PREVENTION IS WORTH A POUND OF CURE -Benjamin Franklin Properly Installed Ground Support Using the McNally System and Steel Sets

4 A L I T T L E R I S K M A N A G E M E N T S AV E S A L O T O F FA N C L E A N I N G - U n a t t r i b u t e d

5 I NTRODUCTION IDENTIFY: WHAT RISKS DOES THE GROUND PRESENT?

6 WHAT IS MEANT BY DIFFICULT GROUND? Particular Geological Features: + Water inflows + High water pressures + Fault zones + Rock bursting + Hard, abrasive rock + Squeezing ground + Fractured rock + Mixed face conditions + Cobbles and boulders

7 BEGINNINGS OF DIFFICULT GROUND SOLUTIONS (DGS): COLLAPSING/SQUEEZING GROUND K A R G I H E P P G E O L O G Y AT T I M E O F T B M O R D E R G E O L O G Y O F P R O J E C T AT 5 0 % C O M P L E T E

8 INTRODUCTION DIFFICULT GROUND SOLUTIONS WHAT IS IT? + Difficult Ground Solutions (DGS) is a suite of options for non-pressurized, shielded TBMs in hard rock and mixed ground + Features are customized for known geologic conditions including squeezing ground, fault zones, water inflows, and collapsing ground

9 ASSESS and MONITOR: TOOLS AND STRATEGIES FOR LEARNING WHAT S AHEAD

10 Risk Comes From Not Knowing What You re Doing - Warren Buffet

11 Heavy Water and Muck Inflow Veligonda, India 10 m Double Shield TBM

12 STRATEGY GOOD GROUND KNOWLEDGE DETECTION Good geological advance investigation within the tunnel is cost effective Probe drilling in advance of face Multiple probe holes in faulted areas Probe drilling in advance of face

13 TUNNELING IN ROCK WITH WATER PROBE DRILLING Capable of accurate drilling at long distances: 60 to 100 m ahead of the TBM

14 TBM DESIGNS PROBE DRILLING 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

15 PROBE DRILLING EQUIPMENT Wasarra DTH water hammers Ideal for drilling in water environment Straighter drilling Drill tests completed near jobsite Ripamonti Drill Feeds Blowout preventers

16 STRATEGY MEASUREMENT WHILE DRILLING (MWD) & OTHER SYSTEMS MWD system and TBM data interprets geological model Understanding the rock mass, improving general performance Documentation of the existing rock formation Amberg TSP System One or more shot lines w/small explosive charges Four receivers Geoelectrical BEAM System Whole cutterhead or single cutting tools can act as measuring electrode

17 FACE COLLAPSE FACE INSPECTION CAMERA Purpose To see the cut face in front of the TBM Allows understanding of ground stability Uses prepositioned ports that pass through the back of the cutterhead

18 TAKING CONTROL: TOOLS AND STRATEGIES FOR MITIGATING THE RISKS OF DIFFICULT GROUND

19 STRATEGY CHEMICAL GROUT Wands pushed into face and chemical additive (Polyurethane) is pumped into the wands to consolidate the face

20 STRATEGY FOREPOLING Typical overlapping forepoling arrangement

21 SMOOTH CUTTERHEAD DESIGN + Purpose A smoother surface does not permit the cutterhead to become stuck due to changing ground conditions and collapse. + Grilled bucket openings + No face buckets

22 STRATEGY HIGH-TORQUE MAIN DRIVES Purpose When loose material comes against the cutterhead higher torque is required to commence rotation. Two speed gearboxes allow both high torque and high speed without increasing HP/KW.

23 Cutterhead Torque (knm) TBM FEATURES FOR DIFFICULT GROUND STRATEGY HIGH-TORQUE MAIN DRIVES Gerede Torque Curve Two-Speed Gearbox Low Speed Dual Range Gearbox: Low RPM/High Torque High RPM/Low Torque High Speed Cutterhead Speed (RPM)

24 TUNNELING IN ROCK WITH WATER WATER INFLOW PREVENTION Three-axis main bearing with 35 bar static pressure protection Outer Seal Layout Inner Seal Layout

25 TUNNELING IN FAULTED & FRACTURED ROCK SEALABLE/REPLACEABLE SCREW CONVEYOR Screw conveyor designed in removable and replaceable sections, with wear plating for use in abrasive ground Screw conveyor can be sealed off so the TBM can continue to advance in water-bearing ground Sequential operation of screw conveyor Replaceable wear plates and sections of screw for use in rock conditions

26 STRATEGY MUCK CHUTE CLOSURE DOORS Purpose is to reduce the volume of incoming water and fines passing through the muck chute Can be flapper door type or guillotine type

27 TUNNELING IN ROCK WITH WATER WATER INFLOW PREVENTION Sealable Pressure Bulkhead

28 Alternative To Muck Chute Closure Doors

29 METHODS & LESSONS LEARNED WATER STRATEGY: SEALING OF DOUBLE SHIELD GAPS

30 STRATEGY RAPID ADVANCE SHIELDS Rapid Advance Shield Design for difficult ground entails a number of features to effectively excavate in squeezing conditions: Shorter shield design Stepped/tapered shields Convergence measuring system Peripheral shield lubrication Hydraulic shield breakout system

31 FACE COLLAPSE COLLAPSE DETECTION CYLINDER (CDC) Purpose Identifies ground when it has started to collapse onto the forward shield of the TBM. Temposonic cylinder to measure distance from shield to ground Read distance measurement from operators screen

32 TUNNELING IN ROCK WITH WATER RAPID ADVANCE SHIELDS Stepped Shield Design Considerations: Fines and muck flow Steering Protection against squeezing ground Shimming of gage cutters Nominal overcut and 50 mm overcut shown

33 TUNNELING IN ROCK WITH WATER RAPID ADVANCE SHIELDS

34 TUNNELING IN ROCK WITH WATER RAPID ADVANCE SHIELDS Peripheral Shield Lubrication

35 STRATEGY 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

36 INTRODUCTION 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 Image credit: Bilgin & Algan (2012). The performance of a TBM in squeezing ground in Uluabat, Turkey. Tunnelling & Underground Space Technology 32:

37 CONCLUSIONS DIFFICULT GROUND SOLUTIONS TAKEAWAY POINTS + Identify the risk it s important to know as much about the ground as possible before you start and equip the TBM with the right tools for the job. + If you re tunneling in the mountains, your geotech will probably not be accurate so it s best to be prepared for everything! + The DGS features should be built into the TBM, rather than being added in the tunnel. + Assess and monitor the risk We have probe drills and many other tools to provide information about what we will be encountering. Use them! + Contractors and project owners must work with the equipment manufacturer from the beginning to develop a solution for challenging projects.

38 THANK YOU!

39 SIDE NOTE: MAIN BEAM TBM