different methods of shaft boring

1. MODERN SHAFT BORING
TECHNOLOGY

2. WHAT IS SHAFT BORING
???
 It is the method of sinking of shafts without the use of
any explosives and drilling-blasting operations
 It involves the use of some advanced technologies of
tunneling used vertically(as shaft are vertical)
 The system consists of a cutter wheel mounted on a
carriage and a clam type mucking unit
 The carriage is mounted on a slew structure that rotates
about the vertical axis of the shaft
 The rock cuttings are mucked into a hopper, which
discharge the muck into sinking kibbles/buckets for its
discharge at the surface

3. o The strata which gives large amount of water, must be
sealed off by grout before the SBM begins boring.
o To unstable ground immediate lining is possible by
making use of walling platform immediately above the
machine installation
o In shaft boring techniques drill string is not required and
the precise verticality of the shaft can be maintained

4. HISTORY OF SHAFT
BORING
 It is the newest and probably the least mature
technology of shaft sinking.
 The concept had been proposed as early as in
1960’s.
 However, problems of muck removal prevailed.
 The Shaft Boring Machine was invented in
Germany in 1978 by Aker Wirth Co.

5. DIFFERENT METHODS
OF SHAFT BORING
 FULL FACE BORING
 SHAFT CORING
 COMBINED METHOD
 RAISE BORING/REAMING

6. FULL FACE BORING
This is a method in which the Shaft Boring Machines are
used directly to bore the shaft.

7. Depending upon the presence of a pilot hole at the centre
there are two further classification of the method
 V-MOLE METHOD
 BLIND-HOLE METHOD

8. THE V-MOLE METHOD
 The method involves the drilling of a pilot hole at the
centre before the starting of operation.
 Diameter of pilot hole ranges from 1.83 to 2.4m.
 Pilot hole serves to remove the rock debris formed
during boring.
 It actually involves reaming the pilot hole
downwards by the use of Shaft Boring Machine.

9.  The machine is laser guided which helps it to drill
vertical holes accurately .
 Shaft diameter in the range 5.0 to 8.5m can be attained
by this method.
 Reaming, muck disposal, shaft support and permanent
shaft equipping are performed continuously and
concurrently.
 The method offers a fast and efficient alternative to
make shafts.

10. A V-MOLE MACHINE

11. THE V-MOLE METHOD

12. THE BLIND HOLE
METHOD
 This method also uses Shaft Boring Machines to
make the shaft.
 Unlike the V-Mole method the central pilot hole is
not drilled in this case.
 Rather the SBM moves down on its own as directed
by the crew.
 The muck is removed from shaft bottom using
clamshell buckets which is later hoisted up to the
surface.

13.  The hoisting system is hydraulically operated from the
surface rig.
 The method is slower compared to V-Mole method as
muck removal constitutes a major part of the cycle time.

14. THE BLIND-HOLE METHOD

15. CORING METHOD
 The method is still in its experimental stage and not
put to full use.
 It involves removing 20-30% of the annular area of
the shaft using conventional drilling techniques.
 The remaining central region is removed as a core
in various stages( hence the name).
 The method is claimed to be most efficient of all
boring methods.

16. COMBINED METHOD
 In this method a part of the rock is brought to the
surface as core and the rest is broken.
 The cuttings are brought to the surface by the use
of any suitable drilling fluid.
 The drilling fluid also serves to prevent caving in of
the shaft sides.

17. RAISE
BORING/REAMING
 This process includes producing a circular
excavation either between two existing levels in an
underground mine or between the surface and an
existing level in a mine.
 First the Boring Machine is setup on an upper level
and a small diameter(around 9”) pilot hole is drilled
usually with a tricone bit down to the lower level

18.  When the hole is completed the drill bit is removed
and replaced by a reamer head having the
diameter same as that of the required raise.
 Roller cutters are mounted on the reamer head .
 When it is rotated and pulled back upward
towards the machine the rock debris falls by
gravity into the lower level from where it is
removed

19. THE RAISE BORING METHOD

20. EQUIPMENTS
 Tricone roller bit
 Rig and the Hoisting system
 Shaft Boring Machine(SBM)
 Reamer Bit

21. EQUIPMENTS
EXPLAINED
 Tricone roller bit:
 Used to drill the pilot hole in case of V-Mole method
and raise boring.
 Shaft Boring Machine(SBM):
 Cutter wheel- used to break the rock at the shaft
bottom
 Disc cutter- these are mounted on the cutter wheel
and are actually responsible to shear break the
rocks.

22.  Clamshell buckets-it loads directly from the
shaft bottom and discharges the muck into
a hopper.
 Hopper- it is a central collecting place for
muck which is later hoisted to the surface.
 Gripper shoes/ring- used to position the
machine in the shaft by engaging the sides
of the shaft.
 Walking cylinders- the allow the machine to
advance up or down the shaft in
increments.
 Swivel- suspends the SBM from the

23. OPERATIONS IN AN
SBM Excavation
 Mucking
 Gripping
 Rock support
 Guidance

24.  Reamer bit:
 It is used to increase the diameter of the previously
drilled pilot hole to attain the desired shaft/raise
diameter.
 It also has disc cutters mounted on it which actually
shear the rock.

25. A REAMER BIT/HEAD

26. COMPARISION WITH CONVENTIONAL
METHODS OF SINKING
SL
NO
Factors Conventional
Sinking
Shaft Boring
1 Depth restrictions None Economical from 800m
2 Diameter
restrictions
None 4.5-8.5m
3 Speed of sink Faster upto 800m Faster from 800m onwards
4 Lining thickness Thicker Thinner
5 Safety aspects Poorer Best
6 Kibble hoist
requirements
Large hoist are
required
Small hoist are sufficient
7 Sinking crew size Large small