SHAFT SINKING

Akshay S KrishnaVNIT Nagpur

Mining the mineral deposits Temporary storage and treatment of

sewage Bridge and other deep foundations Hydraulic lift pits and Wells In conjunction with tunneling system or

network for the purpose of lifts, escalators,stair and ladder-ways,Ventilation, drainage and pumping.

PURPOSES ….

Circular shafts are preferred in almost all situations due to their stability characteristics.

When strata are competent one, such as that in most of the metal mines, rectangular or elliptical shafts give the advantage of proper use of their cross sectional areas

SHAPES ….

Positioning w.r.t to deposit’s geometry

Positioning w.r.t. surface topography

Position w.r.t. geological disturbances, water table and ground conditions

LOCATION ….

Hoist with head gear and suspension gear The scaffold Kibble or sinking buckets Shaft centering devices Muck disposal bins and chutes Shaft ventilators with rigid and flexible

ducting

ITEMS NEEDED ….

Face and main pumps with suction and delivery pipe ranges

Compressed air and water pipelines Portable pneumatic lights Concrete mixers and delivery range Blasting cables

ITEMS NEEDED ….

Power supply Water supply Transport Stores Repairs Refreshment Housing Social life

SERVICES TO BE PROVIDED ….

Reaching up to the rock head

Sinking through the rock

Sinking through the abnormal or difficult ground, if any, using special methods.

BASIC OPERATIONS ….

The ground is excavated using ordinary excavating tools and appliances or by the use of mechanical excavators such as clamshells, backhoes etc.

Cranes are used to hoist the muck if the cover is thick.

If this procedure is not feasible then either the ground should be consolidated prior to carry out any excavation, or a suitable special sinking method should be adopted.

REACHING UPTO THE ROCK HEAD

No blasting should be done to preserve its original strength.

Large area than the finished diameter of the shaft should be excavated taking into account the allowance for the thickness of temporary and permanent linings

The shaft collar is built of the concrete of the required strength and keyed to the bed rock

1. Drilling2. Blasting3.Mucking and Hoisting4. Support or shaft lining5. Auxiliary operations: a) Dewatering b) Ventilation c) Lighting or illumination d) Shaft centering

SINKING THROUGH THE ROCK …

Use of sinkers to drill holes of 32–38 mm. diameter and the shaft jumbos (equipped with number of drifters) to drill holes of 40–55 mm. dia. is made

The hole’s length varies between 1.5 m and 3 m if the sinkers are used, and it can be up to 5 m in case of the shaft jumbos

Wedge cut, pyramid and step cut are the common drilling patterns adopted

DRILLING …

Usually, high-density water resistant explosives, such as N-G based, are used

Use of water or sand-clay mixture can be made to act as a stemming material.

Usually series-parallel connections are made to connect the detonators at the face and this circuit is then connected to the blasting cable suspended in the shaft and leading right up to the surface.

Face is blasted after taking due precautions.

BLASTING .…

Aluminium based water gel explosives (refer sec. 5.4.5) and high frequency electro -magnetically initiated detonators are succesfully used these days

Improved environmental conditions,improved safety due to better shock sensitivity characteristics, Ease of use of loose detonators ,economic advantages are some of the factors favouring Al based gels

BLASTING .…

Another variation is the use of emulsion explosive with booster and Nonel detonators

They have advantages like Less expensive and faster loading than cartridge explosives ,Provides full borehole coupling , Reduce drilling and Better fragmentation.

BLASTING ….

The mucking efficiency depends upon the size of rock fragments, hoisting depth, shaft cross-section and water inflow rate

Several types of shaft muckers are available

Arm loaders such as riddle mucker, cryderman mucker, cactus grab and backhoe mucker

Rocker shovel such as Eimco-630

Scrapers – used for very large dimensioned shafts

MUCKERS ….

CRYDERMAN MUCKER

CACTUS GRAB …

ROCKER SHOVEL ….

SCRAPERS ….

Basically there are two types of lining: Temporary and Permanent. The make of water and strength of the strata through which the sinking operation is to be carried out govern the choice

In some situations temporary support is not required, whereas in others, it becomes essential to protect the crew and equipment from any side fall

LINING ….

They can be of use if the ground through which shaft is to be sunk is loose or unstable such as sand, mud, gravel or alluvium, or when excessive amount of water is encountered, which can not be dealt with the sinking pumps

Piling system,Caisson methods, Cementation,Freezing method,Shaft drilling & Boring are special methods of shaft sinking

SPECIAL METHODS ….

Surface and underground excavations;methods,techniques & equipments - Ratan Raj Tatiya

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