Presentation on Shafts

1. PRESENTATION TOPIC
SHAFT DESIGN AND
SINKING
Presented By Under guidance of
Pramoda G Dr. Balasubramanian A
2nd semester, Geology Professor

2. Shaft Definitions
Shaft- A rotating member used to transmit power.
Axle- A stationary member used as support for rotating elements such as
wheels, idler gears, etc.
Spindle- A short shaft or axle (e.g., head-stock spindle of a lathe).
Stub shaft- A shaft that is integral with a motor, engine or prime mover
and is of a size, shape, and projection as to permit easy connection to
other shafts
Line shaft- A shaft connected to a prime mover and used to transmit
power to one or several machines
Jackshaft- (Sometimes called countershaft). A short shaft that connects a
prime mover with a line shaft or a machine
Flexible shaft- A connector which permits transmission of motion between
two members whose axes are at an angle with each other

3. What does it mean “shaft design”? shaft design ?
1. Material selection
2. Geometric layout
3. Stress and strength: static and fatigue
4. Deflection and rigidity: bending defl., torsional, twisting,
slope at bearings and shaft- supported elements, and shear
deflection due to transverse loading on short shafts.
5. Vibration: critical speed
Material selection
• Many shafts are made from low carbon, cold-drawn or hot-rolled
steel.
• Alloy steel: Nickel chromium and vanadium are steel Nickel, some
of the common alloying materials. However alloy steel is expensive.
• Shafts usually don’t need to be surface hardened unless they serve
as the actual journal of a bearing surface.
• Hardening of surface (wear resistant): case hardening and
carburizing ; cyaniding and nitriding.

4. Purpose of a Shafts
• To access an ore body .
• To transport men and material to from underground workings .
• For hoisting ore and waste from underground.
• Storage of nuclear waste
Shaft Cross Sections
1. Rectangular Shafts
Most shafts that were constructed in the 1900’s were of a rectangular cross-
section because of the shape of the pieces of equipment that were taken
down the shaft i.e. cages, skips, and counterweights were all square or
rectangular in nature and so it made a lot of sense to sink or mine
rectangular shafts. Breaking a square / rectangular shutter was however
problematic and this slowed down the rate of sinking.

5. 2 Circular Shafts
Almost all the hard rock mines now have circular shafts because the
cross section provides good geometry for airflow and good rock
support characteristics. The circular shutter is ease to move when
doing concurrent lining resulting in faster work progress during
sinking operations. This is an important aspect when it comes to the
cash flow of the project.
3 Elliptical Shafts
Elliptical shafts were designed as an alternative to large circular
shafts by simply adding half moons along the main axis. This had the
effect of reducing the circular excavation and therefore the cost of
sinking the shaft.

6. • Identify possible mining layouts
• Define standard mining block (stope or panel size) per
layout
• Calculate steady state conditions per level
• Define steady state inputs/outputs requirements per level
• Determine minimum access dimensions to cater for
equipment and ventilation
• Calculate development requirements to get to steady state
• Simulate full level production from start of block to ore
body extremity
• Determine the maximum number of levels that will operate
simultaneously
Determining the rate of mining can be as follows:

7. 1 Criteria for choosing a Vertical Shaft
A vertical shaft should be chosen under the following conditions:
• Ore body should be steep dipping
• Ideal for deep ore bodies
• Provides quick access to ore body
• Most economic hoisting method for depths exceeding 500m
• Quicker return on capital investment
2 Criteria for choosing a Decline or Inclined Shaft
A decline or inclined shaft should be considered under the
scenarios:
• Flat dipping ore body
• Shallow ore bodies
• Require high throughput
• Require low initial capital costs
• Want to avoid some of the environmental concerns
(headgear)

8. Choosing the Right Shaft
The size or dimensions of each shaft will differ according to the
intended duty for each unit. There are three types, namely:
vertical, decline and
inclined shafts.
a) Narrow tabular deposits (steep & flat dipping – gold,
platinum, etc)
b) Wide tabular deposits (coal, potash)
c) Massive deposits (copper, nickel, iron ore)

9. Different types of shafts
Shaft type Diameters (m) Depths (m)
Mining ventilation 1-6 50-1500
Mining ore passes 3-7 50-1500
Mining access shafts 5-10 50-1500
Water treatment shafts 1-3 20-100
Tunnel access shaft 5-20 10-50

11. Objectives
Introduction
Definition
Shaft collar
Shaft sinking methods
Down-the-hole shaft sinking method
Wood/steel piling
Open caisson
Cementing process
Freezing process
Types of shafts

12. Introduction
shaft sinking, excavation from the surface of an opening in the earth.
Shafts, which are generally vertical, are usually distinguished from tunnels,
which are horizontal.
Little difficulty is experienced in shaft sinking through solid rock, which
contains little water.
Shafts sunk in loose water-bearing soils and lined with cast iron or with concrete
masonry 1 to 2 ft (30-61 cm) thick, built in sections as the work advances.
Shaft sinking through rock is generally accomplished by blasting.
Diameter and depth depends upon the type of the shaft
Shafts are usually circular or rectangular.

13. Definition
Shaft: A vertical or inclined tunnel from surface for the conveyance of
men, materials, hoisting ore, pumping water and providing ventilation.
Sinking: The work in excavating a shaft.
Shaft sinking:
It may be described as an excavation of vertical or inclined tunnel from
surface for conveyance of men, materials, ventilation, pumping water, in
addition to hoisting ore and waste rock.
It is also called Shaft Construction or Shaft Mining.

14. Shaft collar
On the surface of an underground
mine, a collar is required for a shaft or
raise entry, Collars are also required
For ventilation shafts, service shafts,
and for all raises that reach surface.
collars are normally lined with
concrete
Methods of shaft
sinking
There are different methods of shaft sinking/construction. Actually
three possible methods allowing a shaft to me sunk through highly
weathered over burden on the basis of Excavation and Wall support.
These are;
Down-the-hole Shaft sinking Methods
Remote Shaft sinking Methods
Raiseboring Method

15. Down-the-hole-Shaft
sinking method
1. Rock bolting & meshing
2. cast-in-place lining
3. pre-cast lining
1. Drilling & blasting
2. shaft-boring mucking
3. V-mole with pilot hole

16. Excavation method
Drilling & blasting:
A shaft is constructed by drilling holes and filling them with explosives.
Using this method, drilling and blasting can sink around 5-10 metres in one
blast.
This is very labour-intensive, unsafe and has high running costs.
The most viable alternative for shafts up to 100m in length.

17. Mucking:
The operation of loading broken rock by hand or machine, usually in shafts
tunnels.
Note: Muck, any useless material produced in mining.
mucking out cuttings from the bottom of the shaft.
Usually this would require some skip-hoisting, bucket-hoisting or clam-
grab equipment.

19. V-mole with pilot hole
The V-mole is an improvement on the concept of the shaft boring machine.
Before boring, a pilot-hole is drilled, to assist in both cuttings removal and
guiding the machine along the correct path.
The V-mole uses grippers to hold on to the side of the shaft .
The V-mole is a costly machine not suited for drilling short shafts.

20. Wall supporting methods
Rock bolting and meshing
A wire mesh is fastened to the walls with evenly spaced rock bolts.
Rock bolting is a commonly used, cheap method. The rock-bolts increase
normal stresses on joints so that shear failure along joints becomes more
difficult.
Often rock bolts and mesh are used as a basis for shotcreting.
Water in-flow during shotcreting severely reduces the quality of shotcrete.

22. Cast-in-place lining
It is possible to cast concrete rings as the shaft sink progresses.
This method provides a smooth, watertight and permanent lining for the
shaft.
The casing can be reinforced to cope with horizontal stresses (i.e. ring-
shaped reinforcement) making the casing elements more economical.

24. Pre-cast lining segments
In sands, mudstone and sandstone, steel, pre-stressed concrete or composite liners
with a smaller diameter (i.e. up to the 4.5 dia: )than the shaft are lowered after drilling
out the hole.
Concrete can then be poured behind the walls to create the lining.

25. Shaft sinking methods
a) Wood/Steel Piling
The first set of piles, forming a circle around
the shaft site is started at the surface. As
the piles are driven down, the ground is
excavated, and a circular crib is put in every
few feet. In this way the shaft is sunk in a
series of short wooden cylinders.
b) Open Caisson
In this method the shaft is started by
digging a shallow excavation and placing a
cutting shoe on the bottom of the pit. The
ground inside and just under the shoe is
excavated and the lining is built up as the
shoe sinks.

26. c) Cementation Process
Cavities and fissures are filled with quick-setting cement under high
pressure then allowed to set. Cement pumps are designed for
pressure as high as 5000 lb/sqin.
d) Freezing Process
This method was first used in 1883. The wet round is artificially frozen
and then blasted and excavated as though it were solid rock. From 20
50 holes are drilled on the circumference of a circle. Circulating pipes
placed in the holes and a calcium or magnesium chloride solution is
pumped through the pipes to freeze the ground.

27. CONCLUSION
• Shafts for a newly founded ore body or indeed existing ore
reserves.
• The methodology is cannot be avoid the optimization
process to come up with best economic option.
• Shaft must have adequate torsional strength to
transmit torque and not be over stressed.
• Shafts are mounted in bearings and transmit power
through devices such as gears, pulleys, cams and
clutches.
• Shaft must sustain a combination of bending and
torsional loads

28. REFERENCE
1. J.E Shigley and C.R Mischke , Mechanical Engineering
Design , McGraw Hill Publication, 5th Edition. 1989.
2. M.F Spotts, Design of Machine Elements, Prentice Hall
India Pvt. Limited, 6th Edition, 1991.
3. Khurmi, R.S. and Gupta J.K., Text book on Machine
Design, Eurasia Publishing House, New Delhi.
4. Sharma, C.S. and Purohit Kamalesh, Design of Machine
Elements, Prentice Hall of India, New Delhi, 2003.