4 Main Methods of Stone Mining

Stone Mining

According to different environments of stone mines, stone mining methods can be divided into four categories, including splitting mining method, controlled blasting mining method, sawing mining method and combined mining method.

Splitting Mining Method

The splitting mining method is a mining method that uses the splitting characteristics of stone to split and separate stone from ore bodies or stone masses with simple tools, simple machines or expansion agents. It includes wedge cavity wedge fracturing, drilling wedge fracturing, drilling hydraulic fracturing and drilling expansion agent fracturing.

Wedge cavity and wedge-splitting mining are mostly used for manual mining. In the ore body or weathering zone with exposed stone mass and developed fractures, the natural fracture conditions of the ore body can be fully utilized, especially for the mining of protruding stone mass or boulder with several geometric space planes of the stone mass in a free state and only one or two jets connected with the main ore body. This method is suitable for granite mines lacking water and electricity and can be used as an auxiliary mining method for other mining methods. This method is also suitable for mining thin ore bodies of stone with a thickness of 1~2m.

Drilling wedge splitting is a semi-mechanized mining method that uses mechanical drilling instead of manual drilling. Compared with wedge cavity wedge splitting, it has the characteristics of high mining efficiency, low labor intensity, less investment in drilling machine, simple operation and easy to master. If enough stone drills are equipped, a certain mining scale can be formed. This method has strong adaptability and is less affected by the mine temperature and natural conditions. It is mainly used as the main mining method for small and medium-sized granite mines, and can also be used as an auxiliary mining method for disassembling the separation body and trimming granite blocks.

Drilling hydraulic fracturing is to use a stone drill to drill holes and use a hydraulic fracturing machine to replace manual wedge fracturing. With the help of hydraulic thrust, the hydraulic power is transmitted to the wedge compression rod through the piston of the splitter placed in the drill hole in advance to drive the splitting wedge to vertically pressurize the hole wall of the drill hole. Under the action of mechanical pressure, the drill hole in the stone will expand at the most concentrated stress position. If several hydraulic splitters are placed in the row holes arranged along a straight line and pressurized at the same time, the row holes can be split along their connecting lines. Because mechanical splitting is used instead of manual wedge splitting, the consistency of row hole splitting is ensured, the success rate of block disintegration and shaping is improved, the block rate and mining efficiency of stone mining are improved, and the labor intensity of workers is reduced. The drilling hydraulic fracturing mining method can be used for stone mass separation in granite mines with good integrity, but the most commonly used methods are the disintegration of separation bodies and the shaping of blocks.

The principle of borehole expansion agent fracturing mining is the same as that of borehole wedge fracturing and borehole hydraulic fracturing mining, except that the expansion agent is used as the power for stone fracturing. The most widely used expansion agent is expansive cement. During operation, only the expansive cement needs to be mixed with water and poured into the drain hole. In the closed state, it can produce huge expansion pressure. When it is encapsulated in the borehole, the expansion pressure and tension generated are enough to split and separate the stone. Compared with the other two splitting methods, the expansion process of expansive cement is relatively slow, and the drying speed is related to the temperature of the operating environment, the type of expansive agent, the mixing concentration, the borehole diameter and other factors. The drying time under low-temperature environments is several to ten times longer than that under high temperatures. At present, there are various types of expansion agents for use in stone mines under different climatic conditions.

The methods of drilling wedge fracturing and drilling hydraulic fracturing are mining methods that take advantage of the splitting characteristics of stone. In principle, they can be used for the mining of granite and marble. Because most granites have good splitting properties, these two methods are generally used for granite mining. When mining granite, the workload of stone drilling is very large. It is generally necessary to drill 10 m holes to mine the stone with a total amount of ore and stone per cubic meter. If the rate of waste materials is calculated as 30%, it is generally necessary to drill 30~40 m holes to mine the finished waste materials per cubic meter. Of course, the number of boreholes is related to such factors as the splitting characteristics of stone, the quality of boreholes and the correctness of operation methods. The above parameters are only for reference. Many granite mines at home and abroad adopt drilling wedge fracturing, drilling hydraulic fracturing and drilling expansion agent fracturing methods for mining. The drilling equipment used in mining methods such as drilling wedge fracturing and drilling hydraulic fracturing includes pneumatic, internal combustion, liquid seat or electric stone drills. These types of stone drills have high drilling efficiency, good drilling quality and convenient operation. The single-hole perpendicularity and straightness of row holes drilled by multi-head bench drill are better, and the flatness error of row holes is smaller, which is more conducive to improving the success rate of splitting stone.

Because the splitting property of marble is very poor, and the splitting direction is difficult to control, if the splitting method is used for mining, the rate and quality of blocks cannot be guaranteed. Therefore, except for the layered marble ore body with a thickness of 1~2m and the marble ore body with good splitting properties, it is basically not used for marble mining. In some granite mines with poor splitting properties, the splitting mining method is not applicable.

There is also a grooving expansion method. During the operation, the bottom plane of the separation body is cut and separated with a diamond bead saw. On the inner wall of the drilling holes of the other two vertical facades, the stone is separated after grooving and expansion with a grooving device. The method has the advantages of fewer grooving holes, improved working conditions and reduced labor intensity. There are groove lines in the borehole, which will produce a stress concentration effect when subjected to an external force. The stone body will be disconnected orderly along the groove line, and the groove line has a guiding function to ensure that the section of the separated stone block is flat without deflection. The requirements for the quality of the expansion agent are not high, and the mine is easy to achieve the purpose of producing its own expansion agent. In addition, the production cost will also be reduced, and the cost of block mining will be relatively small, which can increase considerable economic benefits for the enterprise.

The splitting mining method can be used for the mining of open pit stone mines, and even for the mining of tunnel or cave stone mines under specific conditions.

Controlled Blasting Method

The controlled blasting mining method is a mining method in which different blasting materials are put into the stone holes, and different ignition methods are used to separate the rocks from the stone mass. In fact, controlled blasting is to control some performance parameters of gunpowder and blasting materials, use blasting agents that are different from conventional gunpowder and other blasting materials, and select appropriate blasting methods, reasonable blasting parameters and corresponding blasting processes to make the stone ore body and block after blasting operations not damaged by blasting, and maintain the strength and characteristics of the original stone. The correct use of the controlled blasting method can ensure that the stone and ore body after blasting separation will not have blasting cracks and other damages. In addition to improving the rate of mined waste materials, it also ensures the rate of waste materials.

Controlled blasting mining can be divided into black powder controlled blasting, No. 2 stone nitrate explosive controlled blasting, metal high-energy incendiary agent controlled blasting, stone burst tube controlled blasting, detonating cord controlled blasting, detonating tube controlled blasting and other methods.

Controlled blasting has been widely used in marble and granite mines. It is characterized by strong adaptability, low requirements for ore body conditions, external natural conditions and operating environment, and simple equipment. Controlled blasting can be carried out in stone mines equipped with stone drills. As the controlled blasting method is simple and easy to operate, has less investment and is quick to take effect, it is very suitable for the mining of stone mines.

As an auxiliary means, controlled blasting is mainly used for the stripping of the surrounding stone of the ore body, the development of the preparation trench, the removal of interlayer and inclusion in the ore body and the secondary crushing, etc. in the mines where marble is mined mechanically. Due to the poor splitting property of marble itself, compared with the method of sawing for marble mining, it is obviously inappropriate to use controlled blasting mining as the main means of separating or disintegrating the separated bodies in marble mining, or even shaping the blocks, because it will bring a lot of waste and loss of the stone, and only a very low rate of blocks can be obtained.

In granite mining, it is precise because of its good splitting characteristics that the controlled blasting mining method has become the most widely used mining method in international granite mines.

From the perspective of safety, the controlled blasting mining method is mainly used for the mining of open-pit stone mines. It should be prohibited to use it in tunnels, especially in cave-type stone mines.

Sawing Mining Method

Sawing mining is a high-quality and high-efficiency mining method for marble. As an auxiliary mining method, it has been gradually used in some processes of granite mining in recent years. The sawing method is a set of mechanized mining systems consisting mainly of stone sawing equipment and other auxiliary equipment. According to the different sawing equipment, the sawing method can be divided into wire rope sawing machine mining, diamond bead sawing mining, arm sawing (diamond mining band saw or chain arm mining saw) mining and circular sawing machine mining for marble blocks, and diamond bead sawing mining and circular sawing machine mining for granite.

In the sawing and mining of the above-mentioned stone materials, except for the circular sawing machine, their common feature is to use the flexible cutting tools with support (arm sawing machine) or without support (diamond bead sawing machine) to cut the stone on the ore body into hexahedral stone separators with huge volume and regular shape, and then the sawing machine itself or other equipment will disassemble and reshape them into hexahedral regular and flat blocks that meet the requirements of commodities. The arm sawing machine can even directly cut and mine qualified blocks with standard volume from the orebody. The single (double) knife stone cutter (large diameter disc mining saw, commonly known as the dog head saw) was invented by the Chinese. It is mainly used in granite mines. It is combined with the bead saw or manual splitting method to form a new granite block mining method. The traditional circular sawing machine is mainly used for mining stones for construction, usually including stones for building walls, ground engineering, road construction, and water conservancy projects, piers, ports, and dams. The types of stones include stone, block stone, slate, block stone, mushroom stone, etc.

When using sawing method to mine stone, there are certain requirements for geological conditions, natural conditions and equipment matching of the ore body. For example, when using a wire rope sawing machine to mine marble, the hardness coefficient of stone ϝ It should be less than 10. For steeply inclined stone ore bodies, the stone mass layer thickness should preferably exceed 10m. Stone ore bodies with small horizontal or inclined angles can be mined by sawing method even though the stone layer thickness is thin, as long as the quarried blocks can meet the requirements of the size and specification of the commodities. Even if there are cracks of different degrees in the stone ore body, sawing method can also be used for mining as long as the required rate of quarrying waste materials can be achieved. However, for stone ore bodies with many karst caves and open fissures, the general sawing method is not applicable, because the quartz mortar, as the cutting abrasive of wire rope sawing machine, and the cooling water of diamond cutter will lose a lot from these open fissures or karst caves, making the sawing machine unable to work normally. However, there is a chain arm sawing machine with dry cutting tools, which can be used in marble mines with karst caves or open fissures because it does not require cooling water. In addition, stone mines using the sawing method must have a sufficient water supply. If the arm diamond mining band saw with water-cooled sawing is used, there are certain requirements for water supply. If the sawing equipment with cooling water is used in a highly cold area, its operation period can only be carried out in the nonfreezing period, and the mining period of the sawing method will be shortened. In addition to adequate water supply, the mines using wire rope sawing machines should also provide sufficient quartz sand. When using the sawing mining method, there are many kinds of special auxiliary equipment required, such as large diameter hydraulic drilling machine or stone drill, hydraulic stone jacking machine, hydraulic or pneumatic bag jacking, hoisting and transportation equipment with a certain lifting capacity, etc.

The characteristics of sawing mining method are that it can cut a large area and mine a larger volume of stone, with strong adaptability, small sawing seam loss, good squareness of mined blocks, high mining efficiency, low comprehensive mining cost, simple equipment operation and low labor intensity of workers.

The diamond bead saw can cut the disassembly or shaping surface as small as 2m2, and the cutting surface of the separation body as large as 150m2 or even larger. It can also cut the horizontal, vertical or inclined cutting surface at any angle according to the natural conditions of the ore body, with a wide range of applications. When using a wire rope stone sawing machine or diamond bead saw, the mining bench with a height of 15m can be sawed; When the armed cutter is used, the sawing depth can also reach 3-6m. When using diamond bead saws to mine granite, the consumption cost of diamond bead ropes decreases gradually with the increase of the volume of the separator. With the increase of the height of the mining bench and the increase of the sawing depth, a larger separator can be obtained, which is beneficial to reduce the impact of cracks on the rate of waste materials and improve the rate of waste materials for mining stone. When using a wire rope sawing machine to mine marble, the width of sawing seam is only 4mm. When using a diamond bead sawing machine to mine marble or granite, the width of sawing seam is only 10-12mm. Even when using an arm sawing machine to mine marble or serpentine stone, the width of sawing seam is only about 40mm. Therefore, the loss caused by sawing seams in sawing mining can be ignored. The block mined by sawing mining method can achieve 6 geometric surfaces smooth, regular and flat. It also has a high mining efficiency. When cutting limestone with diamond bead saws, the efficiency can reach 15~16m2/h, and when sawing hard granite, the efficiency can also reach 3~5m2/h. When sawing relatively soft granite such as Norwegian Blue Pearl, the sawing efficiency can even reach 15m2/h. In addition, the sawing equipment is simple to operate and easy to maintain, and the auxiliary work time for installation in place is short. Therefore, sawing mining method is the most ideal and advanced method for mining stone materials at present.

Combined Mining Method

The combined mining method is a combined mining method formed by combining several methods of splitting mining, controlled blasting mining and sawing mining. Because of the variety and color of each kind of stone, the occurrence of the ore body is different, as well as the geological conditions of the mine, the external and internal conditions of the ore body, and the economic strength of the mining enterprises, it is difficult to use one or several simple basic stone mining methods to cover all the stone mining process systems. Therefore, according to the actual conditions of the mine, it is the most reasonable choice to select the combined mining method that is suitable for stone mining.

Combined Mining Method for Marble

The hardness of marble is low and it is easy to cut, so sawing is the main method to use machinery to mine marble. There are many kinds of equipment for the mechanized mining of marble blocks. Different mining systems can be formed according to the combination of different equipment.

① Mining Marble with Diamond Wire Saw

The marble mechanized mining system, which takes a diamond wire saw machine as the main mining equipment and is equipped with large aperture hydraulic or pneumatic drilling machines, pneumatic drills, hydraulic jacks, hydraulic pushing bags, pneumatic pushing bags, mast cranes, loaders and other auxiliary equipment, is a mechanized mining system that currently uses a wide range of sawing methods to mine marble, and is suitable for hillside open-pit marble mines. The diamond bead sawing machine for marble mining generally adopts the cutting mode of fixed linear speed.

② Mining Marble by Combination of Diamond Wire Saw and Arm Saw

On the basis of a diamond wire sawing mining system, equipped with an arm sawing machine, the marble mechanized mining system can be formed. This mining system is not only suitable for hillside open-pit and plane depression open-pit marble mines but also adopts a special tunnel mining arm saw, which is also the best choice for the mining of tunnel-type and cave-type marble mines. There are two kinds of arm saws: chain arm saws and diamond mining band saws. The chain arm sawing machine uses hard alloy as the cutting tool, which is suitable for the mining of light-colored stones such as marble and limestone below medium hardness. The structure and movement principle of the diamond mining band saw are similar to those of the chain arm saw, and its cutting tool is a diamond cutter head. The diamond mining band saw is characterized by fast cutting speed, and it can also cut hard marble (serpentine) or silicified marble.

Theoretically, this system is the most widely used mechanized marble mining system. In addition, there is also a mining system that is separately combined with an arm saw, which is suitable for the exploitation of marble mines in the open pit type of mountain slopes and flat depressions.

③ Combined Mining System of Diamond Wire Saw and Mobile Mine Stone Cutting Machine

This system is a method of sawing and mining marble, which is developed on the basis of sawing and mining construction stone saws. During mining, the bead saw is used to separate and cut the horizontal plane of the separator first, and the mobile mine stone cutter is used to cut the vertical saw seam with a depth of 650~1850mm on the ore body to directly decompose the ore body into waste materials. The horizontal plane can also be separated by the method of a horizontal dense rows of holes combined with splitting, and then splitting and disassembling the separation body to produce waste materials.

Combined Mining Method for Granite

Granite, as a building material, is characterized by high hardness and is difficult to cut. In domestic granite mining, flame-cutting machines are generally used to dig and develop cutting ditches, and hand-held or bench-mounted stone drills are used to drill and drill row holes, and combined with traditional methods such as splitting machines, manual wedges or controlled blasting. With the continuous improvement of the performance of diamond wire saws, the new mining system of replacing flame cutters with wire saws has been widely used. In addition, a method of quarrying granite with a single (double) cutter and splitting is also used in China.

① Mining Granite with Mechanical Splitting Method

The most typical system for granite mining by the splitting method is a mechanized mining system consisting of a bench-type or wheel-type stone drill as the main mining machine, hydraulic splitting machine, hydraulic jacking machine, hydraulic jacking bag, slow-acting winch, wheel loader, mast crane, flame cutting machine and other equipment.

Most granite mines in China use the relatively primitive manual splitting method. In such mines, hand-held stone drills are often used to drill shallow wedge holes, and manually wedge and split granite, and a cable hoisting and transportation system consisting of a simple derrick crane and a winch are used to hoist and transport stone.

② Mining Granite by Combined Row Hole Drilling and Controlled Blasting

The basic principle of this mining system is basically the same as the above method, but the drilling is basically a parallel row of holes with the same depth as the separation surface. The separation body and the ore bed stone are separated by controlled blasting, and the decomposition of the bulk integral separation body is processed. The hydraulic splitting machine or manual wedge splitting method is only used when disassembling small separation bodies or shaping blocks. In addition to the portable stone drill that can be used to drill the row holes, the row holes in Dayuan are all drilled with a bench drill. From the perspective of mining efficiency, the combined mining efficiency of row-hole drilling and controlled blasting is higher than that of the pure splitting method.

The combination of the splitting method and controlled blasting for granite mining is the basic mining method used by most granite mines at home and abroad at present. The way of drilling and arranging holes marks the level of mechanization and the quality of mined waste materials. Some highly mechanized granite mines at home and abroad use single-head, double-head or pneumatic bench drills with more drill heads to drill row holes, while more advanced granite mines abroad use hydraulic bench drills to drill row holes. In general domestic granite mines, the drilling and drilling of row holes are completed by using a hand-held stone drill, which can only be called semi-mechanized granite mining.

③ Mining Granite with Truck Mounted Stone Drilling System

The vehicle-mounted stone drilling system is a system for mechanized granite mining, in which hydraulic or pneumatic stone drills, hydraulic splitters, loaders, generators or air compressors and other equipment are installed on the same dedicated vehicle. The truck-mounted stone drill is a multi-functional integrated mining system, which is composed of a crawler or tire tractor equipped with a movable arm similar to the working arm of an excavator. The power of the equipment, such as electric power and hydraulic system, comes from the internal combustion engine of the tractor. The end of the movable pipe can be installed with a special drilling bench, hydraulic fracturing machine and other auxiliary tools to complete most mining operations such as row hole drilling, hydraulic fracturing, block displacement, simple stripping of ore body overburden, gravel removal, etc. This machine is very suitable for mining operations in mines lacking water and electricity. At present, the practical vehicle-mounted stone drill system for stone mines has not been produced in China.

④ Granite Mining System Assisted by Diamond Wire Saw

With the increasing maturity of the bead saw mining technology for sawing granite, and the continuous reduction of the cost of cutting granite with bead wire, the system of bead saw participating in granite mining has become the mainstream system of granite mining at home and abroad, and has also become the symbol of the modernization of stone mining. In granite mining, a mechanized granite mining method has been formed, which is mainly composed of diamond bead saws, combined with single and multi-head bench-type stone drills, hydraulic fracturing machines, hydraulic jacking machines, pneumatic and hydraulic jacking bags and other auxiliary mechanical equipment in various structural forms, as well as various hoisting equipment such as mast cranes. These equipment are combined in different forms to form different mining methods. In Brazil, Spain, India and many Nordic countries, which are the major producers of granite blocks abroad, the matching rate of diamond bead saws for granite mining has almost reached 100%.

The diamond wire sawing mining technology not only makes the traditional granite mining work more modern but also improves the poor working conditions of the mine. At the same time, it establishes and consolidates the foundation of non-destructive stone mining technology. It is a mining method conducive to environmental protection and saving stone resources.

⑤ Granite Full Sawing with Diamond Wire Saw

This method is worth popularizing for the exploitation of granite with poor splitting properties and rare varieties. It can protect the block and ore body from being damaged to the greatest extent and can mine a regular block. The diamond wire saw full sawing mining method has been successfully used in domestic granite mines and has achieved good results. Using this method in Sanlida Emerald Green and Jiulongbi Granite Mines in Fujian Province, China, complete sand-sawn blocks that can be used for cutting large slabs have been successfully mined. In emerald green mines, the rate of blocks has also increased from less than 5% to more than 40%.

⑥ Granite Mining with Single/Double Cutter

This is a very innovative stone mining method in China, which has been successful. It uses a single or double cutter for granite mining, which is equipped with a 4.2m saw blade with the largest diameter and combines the splitting method to mine granite. This method has high efficiency and low sawing cost. When the ore body conditions are relatively good, the rate of waste materials can reach more than 40%, and the mining steps formed are very neat. It is a new granite mining method suitable for national conditions and protecting stone resources. However, it is required that the rock stratum structure is stable, the strike is gentle, the rock splitting is good, and the color is single. If the stone pattern is related to the ore body shape and the mining direction is wrong, only the sawing machine with the largest diameter saw blade (4.2m) can be used to meet the requirement that the mining height reaches 1.85m for sand sawing.

⑦ A Tentative Plan for Cavern Mining of Granite with High-Pressure Water Equipment and Diamond Wire Saw

At present, the bead sawing mining method cannot be used to mine granite mines in caves or shafts. It is feasible to adopt special high-pressure water-cutting equipment combined with a diamond wire saw to conduct granite cave or roadway mining from the perspective of technology. This method has been studied abroad but is restricted by the high price of high-pressure water-cutting equipment, a large number of maintenance costs, and high mining costs, this more advanced mining equipment and method are still in the test stage to be further improved. If the various indicators of this technology can reach the level of industrial production, it will bring revolutionary changes in stone mining.

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