DEWATERING TECHNIQUESDEWATERING TECHNIQUES

MINE DRAINAGE TECHNIQUESMINE DRAINAGE TECHNIQUES

DEWATERING A MINEDEWATERING A MINE

By definition;By definition;

To drain out water from a mine,To drain out water from a mine,

To disposed off water from mine,To disposed off water from mine,

To transport water from mine .To transport water from mine .

A mining excavation receiving water from various A mining excavation receiving water from various resources and may generate variety of operational and resources and may generate variety of operational and logistic problems to the mining operations.logistic problems to the mining operations.

DEWATERING A MINEDEWATERING A MINE

Once the water has entered, the excavation has to drain-off that Once the water has entered, the excavation has to drain-off that water from a minewater from a mine

Before the entry of water into excavation, mine should be Before the entry of water into excavation, mine should be prevented from the entry of water.prevented from the entry of water.

Hence, the mine drainage technique are implemented by;Hence, the mine drainage technique are implemented by;

1.1. PREVENTIVE MEASURESPREVENTIVE MEASURES

2.2. PROTECTIVE MEASURES.PROTECTIVE MEASURES.

PREVENTIVE MEASURESPREVENTIVE MEASURES

The technique is used to keep away water from entering The technique is used to keep away water from entering into mine.into mine.

It is more economical to keep water out of mine than to It is more economical to keep water out of mine than to drain it out after it has entered into mine workingsdrain it out after it has entered into mine workings

Each gallon of water that is prevented from entering the Each gallon of water that is prevented from entering the mine, is one less gallon that will have to be collected, mine, is one less gallon that will have to be collected, transported and disposed-off.transported and disposed-off.

The aim of this technique is to prevent or delay inflow or The aim of this technique is to prevent or delay inflow or reduce intensity of water, the following are the measures reduce intensity of water, the following are the measures taken for the prevention;taken for the prevention;

1.1. Reduce, postpone or avoid inflows.Reduce, postpone or avoid inflows.a.a. By locating excavation or shaft in least permeable groundBy locating excavation or shaft in least permeable ground

b.b. By retreat mining from bottom to top.By retreat mining from bottom to top.

2.2. Divert, drain or intercept water near surfaceDivert, drain or intercept water near surfacea.a. Divert drain streams, lakes, rivers etcDivert drain streams, lakes, rivers etc

b.b. Catch water in ditches or in shafts to prevent inflow to the Catch water in ditches or in shafts to prevent inflow to the deeper sections of mine.deeper sections of mine.

3.3. Protective Layers & BarriersProtective Layers & Barriersa.a. By leaving enough solid ground between mine & waterBy leaving enough solid ground between mine & water

b.b. By leaving pillars on fissures to minimize inflow.By leaving pillars on fissures to minimize inflow.

The following precaution can be established to keep away The following precaution can be established to keep away the water from mine or to minimize the inflow;the water from mine or to minimize the inflow;

i.i. Avoiding the sitting of shaft, bore hole and other Avoiding the sitting of shaft, bore hole and other openings in low spots on the surface.openings in low spots on the surface.

ii.ii. Fluming and other measures can prevent surface run-Fluming and other measures can prevent surface run-off entering in mine.off entering in mine.

iii.iii. Preventing the water influx when aquifer might be Preventing the water influx when aquifer might be more difficult.more difficult.

iv.iv. Shafts should have water tight collars sufficiently high Shafts should have water tight collars sufficiently high above ground to prevent water flowing into the shaft.above ground to prevent water flowing into the shaft.

v.v. Some of the more important ways of preventing water influx in Some of the more important ways of preventing water influx in mines include:mines include:

a)a) Design of excavation minimizes breaking to aquifers or to the Design of excavation minimizes breaking to aquifers or to the surface through appropriate width/depth (w/d) ratio.surface through appropriate width/depth (w/d) ratio.

b)b) Proper sitting of shafts to avoid low spots and the use of pre-Proper sitting of shafts to avoid low spots and the use of pre-grouting during sinking and lining of the shafts.grouting during sinking and lining of the shafts.

c)c) Providing adequate pillar support under water bodies or Providing adequate pillar support under water bodies or underground aquifer, or alternatively providing mine pillar underground aquifer, or alternatively providing mine pillar design based on proper w/d ratio.design based on proper w/d ratio.

d)d) Concreting all exploratory drill holes to that water can not Concreting all exploratory drill holes to that water can not accumulate into themaccumulate into them

d)d) Concreting all exploratory drill holes to that water can not Concreting all exploratory drill holes to that water can not accumulate into them,accumulate into them,

e)e) Keeping test holes properly dried ahead of active workings Keeping test holes properly dried ahead of active workings when approaching a suspected abandoned mine using the when approaching a suspected abandoned mine using the old workings as a sump.old workings as a sump.

PROTECTIVE MEASURESPROTECTIVE MEASURES

o It is a technique to drain out the water accumulated in mines.It is a technique to drain out the water accumulated in mines.

o Also called dewatering technique which solely depends upon Also called dewatering technique which solely depends upon the geology, hydrology, hydrogeology of the mining site, the geology, hydrology, hydrogeology of the mining site, mining methods and cost effectiveness.mining methods and cost effectiveness.

o To minimize the problems associated with influx of unwanted To minimize the problems associated with influx of unwanted water into underground mines, a three step process of water into underground mines, a three step process of drainage, which is following;drainage, which is following;

DEWATERING TECHNIQUESDEWATERING TECHNIQUES

WATER COLLECTIONWATER COLLECTION

WATER TRANPORTATIONWATER TRANPORTATION

WATER DISPOSALWATER DISPOSAL

COLLECTIONCOLLECTION

It is the first stage of dewatering system.It is the first stage of dewatering system.

When prevention of mine water becomes ineffective then When prevention of mine water becomes ineffective then appropriate collection should be there so that the water appropriate collection should be there so that the water from mines is collected at a suitable place from where it from mines is collected at a suitable place from where it can be transported or pumped-outcan be transported or pumped-out

The water in mine should be collected with the help of The water in mine should be collected with the help of SUMPSSUMPS

SUMPSUMP

The sumps are made to collect water in mines (reservoir), and The sumps are made to collect water in mines (reservoir), and the main sump is made up of bricks and cement.the main sump is made up of bricks and cement.

The capacity of sumps depends upon the quantity of water. The capacity of sumps depends upon the quantity of water.

The necessary characteristics of a sump are;The necessary characteristics of a sump are;

The main or final sump must be deep enough to carry the entire The main or final sump must be deep enough to carry the entire water rushed into minewater rushed into mine

If necessary, the secondary sump, or intermediate sump, or If necessary, the secondary sump, or intermediate sump, or temporary sump at a shallower level should be constructed to temporary sump at a shallower level should be constructed to improve condition.improve condition.

SUMPSUMP

Water flowing towards the sump will also carry fines, which may Water flowing towards the sump will also carry fines, which may be abrasive so it will damage the pumping equipments,be abrasive so it will damage the pumping equipments,

To reduce it, fines should be stopped by sedimentation and To reduce it, fines should be stopped by sedimentation and filtration processes,filtration processes,

For that purpose, sump may be lined with gravel.For that purpose, sump may be lined with gravel.

The size of the sump should be larger than that necessary to, The size of the sump should be larger than that necessary to, physically accommodate the pumps,physically accommodate the pumps,

There should be a provision of enough space between sump There should be a provision of enough space between sump and pumps.and pumps.

If there is the use of submersible pump, it is preferably be If there is the use of submersible pump, it is preferably be suspended at least 1ft (300mm) above the bottom of the sump suspended at least 1ft (300mm) above the bottom of the sump to protect the pump from the entry of fines.to protect the pump from the entry of fines.

If sediments accumulates in the sump, cleaning & maintenance If sediments accumulates in the sump, cleaning & maintenance of pumps must be done periodically.of pumps must be done periodically.

TRANSPORTATION OF MINE WATERTRANSPORTATION OF MINE WATER

Mine water transporting means pumping of mine water Mine water transporting means pumping of mine water

Where gravity is not possible for water movements in mine, Where gravity is not possible for water movements in mine, some means of transporting or pumping is required.some means of transporting or pumping is required.

Pumping is established with use of PUMPS and PIPES.Pumping is established with use of PUMPS and PIPES.

It is necessary to design effective drainage system for an It is necessary to design effective drainage system for an underground mine.underground mine.

DESIGNING EFFECTIVE UNDERGROUND DESIGNING EFFECTIVE UNDERGROUND DRAINAGE SYSTEMDRAINAGE SYSTEM

To analyze any pumping requirements, certain design To analyze any pumping requirements, certain design parameters must be considered, including;parameters must be considered, including;

1)1) The inputs of mine environment,The inputs of mine environment,

2)2) The output of mine environment,The output of mine environment,

3)3) The available system engineering of dewatering. the The available system engineering of dewatering. the inputs inputs through outputs for disposal.through outputs for disposal.

Note:- knowledge of all three parameters is necessary to deal Note:- knowledge of all three parameters is necessary to deal effectively with the drainage problem of the underground mine effectively with the drainage problem of the underground mine environment.environment.

1.1. INPUTS OF THE MINE ENVIRONMENTSINPUTS OF THE MINE ENVIRONMENTS

Water inputs to the mine environment include:Water inputs to the mine environment include:

Surface run-offSurface run-off

Strata/seam leakage and leakage from old worksStrata/seam leakage and leakage from old works

AquifersAquifers

Leakage of the system (valves, splices, adapters, pin holes etc.Leakage of the system (valves, splices, adapters, pin holes etc.

Accumulation of water from dust sprays or dust suppressions. Accumulation of water from dust sprays or dust suppressions.

Knowing & understanding of the sources of water inputs is Knowing & understanding of the sources of water inputs is necessary to choose the best location for the main mine sump necessary to choose the best location for the main mine sump or intermediate pumping station.or intermediate pumping station.

As well as trying to prevent/control the input of water into the As well as trying to prevent/control the input of water into the mine workingsmine workings

One must look at the makeup and the quality of the water input One must look at the makeup and the quality of the water input beside amount of water in mine.beside amount of water in mine.

In many mines, the water makeup contains particles and In many mines, the water makeup contains particles and sediments from the mining operations which can turn clear sediments from the mining operations which can turn clear water into sludge.water into sludge.

The efficiency and useful life of any pump depends upon the The efficiency and useful life of any pump depends upon the type of material in water (abrasive or acidic) to be handled.type of material in water (abrasive or acidic) to be handled.

In the selection, for example, a turbine pump may better be In the selection, for example, a turbine pump may better be used for the mixture of water, coal, and rock than the centrifugal used for the mixture of water, coal, and rock than the centrifugal pump with higher head.pump with higher head.

The quality of mine water refer to the pH balance and the The quality of mine water refer to the pH balance and the chemical components of the mine water.chemical components of the mine water.

Acidic mine water (pH less than 5.0) is the real environmental Acidic mine water (pH less than 5.0) is the real environmental problem which must be controlled before it leaves the mine problem which must be controlled before it leaves the mine property.property.

2.2. OUTPUT FROM MINE ENVIRONMENTOUTPUT FROM MINE ENVIRONMENT

If prevention of water inputs into mining operation can not If prevention of water inputs into mining operation can not stop all the nuisance water, the output system must be stop all the nuisance water, the output system must be consideredconsidered

Output system contains three separate elements based on Output system contains three separate elements based on the scope of the system.the scope of the system.

These are;These are;

1.1. The run-off drainage system which described the efforts and The run-off drainage system which described the efforts and methods needed to collect the water inputs and channel them methods needed to collect the water inputs and channel them into the drain network.into the drain network.

2.2. The sump interface encompassing the excavation and The sump interface encompassing the excavation and construction requirements necessary for storage and surge construction requirements necessary for storage and surge capabilities of the pumping network.capabilities of the pumping network.

3.3. The pumping network which defines the necessary The pumping network which defines the necessary equipments for efficient transport of the mine water for final equipments for efficient transport of the mine water for final disposal, including the pumps, piping, valves and pump disposal, including the pumps, piping, valves and pump controls.controls.

3.3. SYSTEM ENGINEERING OR ENGINEERING SYSTEM ENGINEERING OR ENGINEERING THE SYSTEMTHE SYSTEM

To simplify the system of dewatering, in the initial stage of To simplify the system of dewatering, in the initial stage of the mine drainage design,the mine drainage design,

The system can be divided into two major sections;The system can be divided into two major sections;

I.I. Drainage system from the working face to the main sump,Drainage system from the working face to the main sump,

II.II. System from main sump to the surface.System from main sump to the surface.

Note:- once the system has been separated into two parts, the Note:- once the system has been separated into two parts, the mining engineer should begin summing up the mine water mining engineer should begin summing up the mine water inputs from working face to be handled.inputs from working face to be handled.

Parameters from the mine inputs will define;Parameters from the mine inputs will define;

• Minimum pumping rate,Minimum pumping rate,

• Power sources and requirements,Power sources and requirements,

• Sump capacity and location,Sump capacity and location,

• Heavy drainage area,Heavy drainage area,

• Construction requirements for the final design.Construction requirements for the final design.