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Extraction

Building Stone Extraction

Abstract

In respect to building stone resources, Iran is the 4th country in the whole world, but unfortunately due to technical issues in processing, the country is yet to achieve an appropriate market share in global market. Counties with high global market share, possess higher technology of quarrying. Extraction technology has a very decisive influence on economic efficiency of the project. Physical and mechanical properties of the stone should be considered while selecting the suitable method of extraction. One of the best and most popular procedures is deploying wire saws. Advantages of this method include extraction with explosives and capability of line cutting. Nowadays, as explosives have been banned, so wire saws and chemicals are the most popular methods in Iran. In this article, we have tried to introduce different extraction methods and mention their advantages and disadvantages.

Key Words: Dimension Stone, Extraction Technology, Adamantine Wire Saw, Expansive Chemicals, Line Cutting Method

Introduction

Mining industry has greatly developed in recent years, and considering this, open-pit mining is widely applied in many precious quarries of Iran. Iran owns great resources of dimension stones; however, there are many obstacles that have prevented it from achieving a good market share in the world. In particular, inappropriate methods for production, extraction and processing, especially for hard stone, like Granite, are the reason behind this problem.

There are various methods for extraction of dimension stones, such as laser, water jet and explosives, but all of them have problems. Being expensive, having limited equipment, and low quality are some of the disadvantages. The most common method is using wire saws and expansive chemicals.

Common Terms

Block: A piece of stone with at least 500 Kg weight to 20 tonnes.

Square: A square piece of stone with 10 tonnes weight

Slab: A large, thick, flat piece of stone, produced from cutting cops and squares in stone cutting factories.

Crushed Stone: Shapeless stone that is produced while cutting and extracting squares and cops.

Flower Pot Stones: Crushed stones that are useful for producing ornamental things. In Onyx quarries, crushed stones weighing less than 500 Kg are considered in this category.

Stones with the following properties are able to be mechanically quarried:

  • No Alteration
  • No cracks and seals
  • No schistosity
  • Being polishable
  • Acceptable Hardness
  • Extraction conditions being favorable
  • Sufficient resource and being economically viable

Key Factors in Selecting Optimal Extraction Method

  • Geological Features
  • Economic Infrastructure
  • Resource Quantity
  • Combining Different Methods: In respect to topography, a combination of methods may be more economic and suitable.
  • Country’s Legislation
  • Rarity and quality of the Stone
  • Type of use

Various Extraction Methods

1- Line Cutting

2- Car Cutting

3- Water Jet

4- Jet Burner or Flaming Jet

5- Steel Wire Saw

6- Diamond Wire Saw

7- Expansive Chemicals

1- Line Cutting Method

This is the oldest procedure of extraction. In this method some holes are dug on a line, with specific distance. The amount of distance depends on the stones, its density and strength. The block is cut more easily if the distance between holes is decreased; however, the more holes means the more money. As a result it is very important to determine the optimal distance for every stone, through experiments.

Number of holes in each block lowers as width and length of block increase. Therefore it is more profitable to produce blocks with more length and width. It should be also considered that size of block, is dependent on the conditions of mine and available equipment.  Depth of holes is determined in respect to type of stone and height of the block, For instance, the ratio (depth of holes to height of block) is 0.8 for Granite, 0.33 to 0.5 for Limestone and 0.66 for Onyx. This method is much more appropriate for Travertine quarries, and also Granite quarries, due to its hardness.

After boring holes, it’s time to extricate the blocks, which is conducted in 3 different ways:

1-1- Wedge and Blades

In This method, 2 metal blades and a metal wedge are put into the hole (as shown in figure 1), then the wedge is hit by a 10 Kg sledgehammer until the stone is cut.

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Wedge and Blades Method

 

1-2- Mechanical Method (Blades and Rock Splitter)

A Hydraulic hammer is deployed to cut into stone, the advantage of this procedure is the less time and physical power that it needs. The needed impetus is provided by electricity or compressed air, and sometimes a gasoline engine might be used.

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Mechanical Method

1-3- Explosives

In Granite quarries, at first some horizontal and vertical holes are bored and then explosives are used to cut the block. In this procedure, explosive material that have low density and explosion speed are used, like “K – Pipe charge”.

2- Car Cutting Method

Stone cutting machines are very efficient but when it comes to hard stones like Granite, their efficiency is extremely decreased. In this method, machines are deployed to cut blocks and minimizing machinery transportation is a goal to achieve

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Stone Cutting Machines in Action

Car cutting machines are split into 3 different categories:

2-1- Stone Cutting Machines Using Chain

This machine can cut stones both horizontally and vertically. Generally this method has some disadvantages in comparison to diamond wire saw:

1- Depth of cutting is limited to 40 mm

2- It is 30% more expensive, due to greater cutting depth

3- Higher maintenance costs

4- More expertise is demanded

5- Limited cutting depth

However, the advantages include:

1- 40% higher cutting velocity

2- Cutting rear surface of blocks is easier and also quicker

3- Safer

4- It does not need digging holes, so this helps compensate for the extra costs.

2-2- Stone Cutting Machines Using Discs

The discs are identical to the one used in stone cutting factories, by using diamond or more expensive alloy for discs, cutting velocity rises and it will also be able to cut Granite.

2-3- Stone Cutting Machines Using Mill

Unlike machines that use discs, this machine is invented to produce large blocks. The mill is moved by a gear powered by the engine.

2-4- Advantages of Stone Cutting Machine

1- 40% higher cutting velocity

2- Cutting rear surface of blocks is easier and also quicker

3- Safer

4- It does not need digging holes, so this helps compensate for the extra costs.

5- High quality

6- Little noise

2-5- Disadvantages of Stone Cutting Machine

1- Depth of cutting is less than diamond wire saw method

2- It is approximately 30% more expensive

3- Higher maintenance costs

4- More expertise is demanded

5- Limited cutting depth

6- Geometrical status

3- Hydromechanical Method (Water Jet)

In this procedure, a narrow jet of water is applied to the area with high pressure and cut through the block. Special nozzles are deployed and needed power is provided by hydraulic engines.

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Water Jet and its Components

4- Jet Burner (Flaming Jet)

In this method, by means of flame, a cutting as wide as 70 to 100 mm is dug in blocks. As a matter of fact, cutting is produced by burning and melting the block. Heat is provided by gas oil as main fuel, but compressed air may also be available. The cutting process is performed by operator and the produced flame is 1200 Celsius hot. Due to the expansion caused by heat, the surface of block falls apart. 40 to 50 liter of fuel is consumed per 1 square meter of cutting. This procedure is not very popular because of its high fuel consumption and problems related to protection of workers against heat; however only in some Granite quarries that other options are also expensive, this method is deployed.

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Flaming Jet Method

 

5- Steel Wire Saw Method

Deploying this procedure dates from about 100 years ago, in European countries such as Italy. First of all, some holes as long as 30 meters are dug and then steel wires are put in the holes. The base of the process is revolving movement of a steel wire accompanied by Silica powder and water. The system is consisted of a power unit, some pulleys and a tension producer unit. To provide this tension, some hanging weights are applied, this helps cutting both horizontal and vertical surfaces.

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Steel Wire Saw

5-1- Advantages of Steel Wire Saw Method

  • Capability of cutting large areas (2000 m2)
  • Capability of being used in far places
  • Useful for underground mines
  • Vertical and horizontal operation
  • Simple design and easy maintenance
  • Capability of producing block with suitable shape
  • Low energy consumption
  • High efficiency for carbonate stone like Marble

5-2- Disadvantages of Steel Wire Saw Method

  • High costs
  • Complexity of machinery
  • Water pumping dificulties
  • Providing silica powder problems
  • Low cutting velocity (1 m/hr)
  • Decay of wire and material
  • Installing equipment takes too long
  • Wire may be torn or stuck

6- Diamond Wire Saw

There are a 25 to 45 meter (150 m maximum)long diamond wire and a pulley, which help cut the stone. First of all two perpendicular holes are dug in the stone, and then diamond wire is applied. The machine moves automatically on rails by electronic and hydraulic equipment. Tension in the wire is about 100 to 150 Kg and is maintained. The machine can cut both vertically and horizontally only by changing the axis of the wire. Horizontall cutting should be started before vertical one has begun, because the block may fall off and press the wire adversely. Finally hydraulic jacks are deployed for transportation of cut blocks.

6-1- Machines Used in Diamond Wire Saw Method

1- Cutting Machine: Consisted of engine, pulleys and rails

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Cutting Machine Used in Diamond Wire Saw Method

2- Diamond Wire: Consisted of diamond segment, metal spring, safety rings, space rings, metal wire

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Diamond Wire Saw Components

 

There are different wires available for cutting stones with various level of hardness, and wire movement speed is also dependent on the hardness. It is 20-30 m/s for hard stones and 30-36 m/s for china stone and marble.

Cutting velocity depends on type and quality of the stone, in marble quarries it is about 4-7 m2/hr and in decent condition it may be 9. Diamond wire components decay easily due to friction between wire and stone. Therefore, after 200 to 300 m2 of cutting, metal components like springs should be replaced. For better efficiency and safety it is recommended to check diamond wire every day. A safety ring is deployed to prevent the components from being tossed, when wire is cut. So only 5 segments and springs will be detached from cable.

6-2- Parameters Which Influence Efficiency

The most important point is to produce blocks by minimum cost. Many parameters are effective in cutting operation which are divided into 2 categories as relatively controllable and uncontrollable. Uncontrollable parameters include physical and mechanical properties of the stone which must be determined before cutting operation. Secondly by adjusting relatively controllable parameters a decent cutting operation is achievable. These parameters are shown in table:

Parameters Which Influence Efficiency

 

Uncontrollable Parameters Relatively Controllable Parameters
Stone Properties / Hardness Strength Cutting Machine Properties / Operation Properties

 

Water Content

Degree of Alteration

Condition of Discontinuities

Components of StonePowerWire Velocity

Diamond Segment Structure

Dimension of Block

Geometry of Wire While Cutting

Machine Oscillation

Water UsageTechnical PersonnelApplied Technics

As segments decay, cutting rate and efficiency of the wire decrease and cost of operation rises. It is very crucial to minimize decay and maximize efficiency by adjusting operation condition.

6-3- Advantages of Diamond Wire Saw Method

  • Wide Range of Application
  • Need to fewer labor force
  • Noise-free Operation
  • No Powder particles or Oscillation
  • High Efficiency
  • Low Waste
  • High Quality of the Produced block for processing
  • Capability of Cutting in Large Dimension
  • No Stone Tossing

6-4- Disadvantages

  • Need to Preliminary Boring
  • Water Provision
  • High Operative Cost
  • Need to Skilled Personnel

7- Expansive Chemicals Method

Nowadays mining has progressed greatly, and many companies and institutes have invented material and methods which have the highest efficiency and lowest cost and are also environment-friendly.

One of the things that is getting increasingly popular is expansive powder. The mechanism of this method is more similar to wedge and blade method rather than the explosive material method. First of all parallel holes must be bored and then a mixture of this powder and water should be applied into the holes. After a while the mixture expands and applies great pressure into the holes walls. These powders are classified into different types as FRACT.AG, Dexpan, Ket-Rac and Estimat.

7-1- FRACT.AG: FRACT.AG is a highly expansive mortar to demolish and cut rocks and concretes. FRACT.AG swells when poured into a hole and develops a pressure higher than 8000 t/m2 on the holes walls. Thereby breaking them open. FRACT.AG is environmentally friendly because it releases no toxic fumes or harmful substances of any kind. This powder is effective from sub-zero temperature to 70 Celsius and is available in 6 different types in respect to environment temperature. Isfahan, Lavasan and Meybod Granite quarries are the most important quarries that use FRACT.AG in Iran. Low cost and no need to heavy machinery are some of this method’s advantages.

7-1-1- Advantages of FRACT.AG

  • Compatible with environment temperature
  • Adjustable Operation Speed
  • Low Powder Usage
  • Easily Applied to Horizontal holes
  • Capability of Being Pumped
  • No Toxic Gas Emission
  • High Compressive Stress
  • No need to completely boring a hole
  • Low Cost
  • No Need to Heavy Machinery
  • Long Distance Between Holes
  • No Need to Pure Water
  • Squared or Rectangular Shape of Produced Stones

 

 

7-2- Dexpan

This is more popular in the United States for extraction of building stones.

7-3- Ket-Rac

This a chemical that applies tension into holes walls, and does not produce great amount of gas and heat but the result is similar to explosion. This chemical is also used in Iran.

7-4- Stamite

This chemical is less expensive than others; however, high operative costs and less amount of extraction leads to high final cost. It is noise-free and also without any danger but is less popular in mines. Stamite is available in 4 various types, and each one is suitable for a specific environment temperature. One the most significant disadvantage of this method is its late or no reaction and the fact that it is not useful for cutting floors.

7-5- Advantages of Expansive Chemicals

  • No Need to Explosives
  • Easy Application: This method does not need skilled labor force and can be instructed easily
  • Easy Transportation
  • Arbitrary Cutting Shape
  • Environment Friendly: Generally expansive powders are consisted of natural mineral which means they are not harmful to the environment

7-6- Disadvantages

  • Non-standard Production: Most of available powders in Iran are not produced according to the standards, due to financial reasons. Therefore most of the production lacks desired quality.
  • Weather Condition: In Iran, There are not various powders for different weather conditions, and the same powder is used in cold/hot regions of the country. As a result, in cold areas the efficiency of the operation decreases substantially.
  • Danger of Explosion
  • Small Dimension of Cut Blocks
  • Health Issues: Many people who work with powders produced in Iran, have reported that they are experiencing eye and lung problems, although the connection yet to be proved. However the application of cheap material in the production of the powders may be the reason. Also emission of toxic gasses from these non-standard powders is possible.

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Expansive Chemicals

 

Popular Extraction Methods in Iran

Building stone industry has 80 billion dollars turnover per year, and Iran can take a 10% of this amount and has 8 billion dollars of export. Until 1366 most miners didn’t pay attention to extraction method but making more money was more important to them. In respect to profitability of dimension stones, many investors chose that without much experience. In 1366, dimension stone council decided to change extraction method from explosive into modern procedures. And in the second Symposium of mining in Kerman, they decided that only mines that do not deploy explosive methods can be exploited.

Currently wire saw method is deployed in 90% of the mines of Iran. Other methods include: expansive chemicals (ket-rak), wedge and blades, steel wire saw, car cutting.

References

  1. Fatemi, A. Parvin, 2004, Technical and Economical Examination of Steel Wire Saw Method for Extraction of Granite, 1st Conference on Mine Engineering, Tarbiat Modares University
  2. Sharifi, 1988, Building Stones and Their Role in Iran’s Economy, 1st Seminar on Building Stones
  3. Bakhtiari, H. Mirzayee, 1999, Guide to Dimension Stone Selection, Road, Housing and Urban Development Research Center
  4. Iran Stone Magazine, Autumn and Winter of 2005, No. 286 and 287
  5. Khodadadi, 2002, Design of Dimension Stone Quarry, Using Steel Wire Saw Method, Master of Science Thesis, University of Tarbiat Modares
  6. Hamidi Anaraki, 1996, Non-explosive Extraction Methods, Geological Survey of Iran
  7. Fazel Bastami, 2006, (Extraction of) Building Stones, Roshan Rooz Publication
  8. Fahimi Far, 2002, Competitiveness of Building Stone Processing Plants in the World Market, Report of the 2nd and 3rd Stage of Industrial and Educational Research Plan, Iran’s Ministry of Industry, Mine and Trade
  9. Filgueira, M., Pinatti, DG. (2005), In Situ diamond wires: diameter determination of the external cutting rope, International Journal of Refractory Metals & Hard Materials, Vol. 23, PP. 85-90 Published by Elsevier Ltd.
  10. Filgueira, M., (2000), In Situ diamond wires Production. PhD thesis. State University of North Fluminense, Advanced Materials Lab.
  11. Thoreau B., (1984), Diamond impregnated wire for sawing hard abrasive stones, Ind. Diam. Rev. 2, , 94 – 95.
  12. trentec.com.
  13. Summers, D. A. and Lehnhoff, T. F. (1977), Water Jet Drilling in Sandstone and Granite, Proc. 18thSymposium on Rock Mechancis,PP.243-244.
  14. Sharma, S. (2005), Cost Effective Granite Extraction Techniques.
  15. Bhardwaj, G. S. & Sharma, S. (2010), Granite extraction and treatment techniques, Mining Engineers Journal.
  16. http://www.forum.98ia.com
  17. http://Kardolamas.com/fract-ag
  18. http://www.smtnews.ir
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