Upload
niaz-huassain-shahani
View
1.604
Download
113
Embed Size (px)
DESCRIPTION
shaft design for underground mines, for the ore passing, .ventilation, uses in get workers and equipments into or out on the surface etc....
Citation preview
PRESENTATION TOPICSHAFT SINKING
PRESENTED BYNIAZ M SHAHANI-11MN69 (GL)
AFTAB ALI KHOSO-11MN73NASIR ALI MIRJAT-11MN80NOMAN KHATRI-11MN76
DEPARTMENT OF MINING ENGINEERING MUET JAMSHORO
(11-04-2014)
SHAFT SINKING
Objectives
IntroductionDefinitionShaft collarShaft sinking methods Down-the-hole shaft sinking methodWood/steel pilingOpen caissonCementing processFreezing processTypes of shafts
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.
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.
Shaft collarOn 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 withconcrete
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;
1. Down-the-hole Shaft sinking Methods
2. Remote Shaft sinking Methods
3. Raiseboring Method
Down-the-hole-Shaft
sinking method
Wall support
1. Rock bolting & meshing
2. cast-in-place lining
3. pre-cast lining
Wall support
1. Drilling & blasting
2. shaft-boring mucking
3. V-mole with pilot hole
W a ll s u p p o r t
Excavation methodDrilling & 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.
Mucking:The operation of loading broken rock by hand or machine, usually in shafts or 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-shell-grab
equipment.
V-mole with pilot holeThe 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.
Wall supporting methodsRock 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.
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.
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.
Shaft sinking methods
a) Wood/Steel PilingThe first set of piles, forming a circle aroundthe shaft site is started at the surface. Asthe piles are driven down, the ground isexcavated, and a circular crib is put in everyfew feet. In this way the shaft is sunk in aseries of short wooden cylinders.
b) Open CaissonIn this method the shaft is started bydigging a shallow excavation and placing acutting shoe on the bottom of the pit. Theground inside and just under the shoe isexcavated and the lining is built up as theshoe sinks.
c) Cementation ProcessCavities 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 ProcessThis 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 to 50
holes are drilled on the circumference of a circle. Circulating pipes are
placed in the holes and a calcium or magnesium chloride solution is
pumped through the pipes to freeze the ground.
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