Filling mining technology

The filling mining method refers to a mining method in which a goaf is filled with a filling while accompanying the mining, transportation and other operations. The purpose of the filling is to support the two gangs of rock in the goaf, and to build the bottom plate for the stratification of the above. It is suitable for the ore and surrounding rock instability, not allowed to have a larger exposed surface of the deposit; the need to protect the surface of the deposit; rare precious metal or high-grade deposits; pyrophoric sulfide deposits; complex occurrence conditions of deposit, etc. .

Filling purpose

1) Support the rock formation and control the pressure of the mining site;

(2) Preventing surface subsidence and protecting surface features;

(3) Provide a working platform to continue to pick up (similar to the function of the retention method);

(4) Improve the stress state of the pillar (from uniaxial compression to triaxial compression) to ensure maximum recovery of mineral resources;

(5) to ensure the safe recovery of high-sulfur deposits with the danger of internal flash fire;

(6) Control deep rock mining rockburst and reduce deep ground temperature;

(7) to ensure the safety of production during open pit and underground joint mining;

(8) Dispose of the same body waste and protect the environment.

Applicable conditions

First, the mining of high-grade rich ore, and requires a relatively high recovery rate and a relatively low depletion rate; or mining of precious metals.

2. Deposits with conditional parts and mining technical conditions, such as:

1. Hydrogeological conditions and ore body shape are more complicated;

2. The ore body is buried deep and the ground pressure is large;

3. The ore or surrounding rock has the danger of spontaneous combustion;

4. The surface or surrounding rock is not allowed to have large area subsidence or violent movement and requires special protection;

5. Mining at the same time in the open air and underground.

3. Suitable for deposits where the ore is stable and the surrounding rock is unstable.

If special support methods or down-stratified filling methods can be used, it can also be used to open ore bodies that are unstable to the ore.

4. Suitable for mining steeply inclined ore bodies

Because the steeply inclined ore body facilitates the feeding of the filling to the stope, and can reduce the space of filling and the area of ​​the filling top. However, if it can be filled with hydraulic or wind power, it can also be used in the mining of gently inclined thin veins.

Filling process

1 filling material

The latest results of the study Nugget plaster Filling the Australian Mount Isa, the design principles stone paste filling. Through several large-scale agitation tests and free fall tests, it was shown that the block gypsum filling can form a uniform filling body. The block gypsum filler is composed of a graded tailings cement slurry and a proportion of block stones, which exhibit similar bond paste characteristics. The compressive strength exceeds 1 Mpa under the condition of an average addition of 1.5% to 2% of cement.

The Williams mine in Canada uses a stabilizer called DELVO, which is used in the block cementing process. As a result, DELVO stabilizers help to reduce pipe blockage and increase strength. After using this stabilizer, the number of cleaning of the surface mixing tank was also reduced by 45%.

The Savuka mine in South Africa uses BF98 plasticizer, which contains gypsum, which acts to increase the filler concentration and reduce the loss of water and fine particles. Plasticizers also ensure increased flow rates at high concentrations and reduce pipe wear and maintenance costs.

Hecla Corporation of the United States has studied the use of Pozzlith 344N blending agent to reduce the amount of filler gelling agent and improve the fluidity of the filler. The result is a 20% reduction in the amount of cement that does not affect the filling strength and fluidity.

2 Filling mechanics

The University of Montreal in Canada has studied a new method for testing stress and strain in on-site fillings. The traditional approach is to combine borehole sampling with indoor model testing. The new method is to use a new set of equipment, which can drill holes by itself, install stress and strain sensors inside the drill bit, the signal is transmitted back to the working surface through the cable, and there is a protective layer between the drill tool and the sensor to prevent the sensor from being generated during the drilling process. interference. The average drilling speed is 0.1 m/min. Calculated by 8 hours per shift, 7 sets of data can be measured per shift. The advantage of this method is that it does not affect mining operations.

The American Institute for Occupational Safety and Health studied the relative displacement of the surrounding rock from the lucky Friday mine to the stope, the interaction between the cementation load and the steel bar. Eight stratified data were collected showing that the displacement of the surrounding rock caused the deformation of the filling body, thereby applying a load to the vertical anchor in the filling. The results analysis shows that the backing support system with steel anchors is effective.

Russia's Sergey N. Zhurin conducted a pore pressure control test for tailings discharged tailings. The test experiment was done in Gubkin iron ore, more than 80% of the tail water is pumped to the two mortar test stope observed distribution hole filling pressure zone plate, while the hole filling body also analyzed by FEM model numbers Pressure distribution. The results of the on-site investigation revealed that there is no correlation between the pore pressures in the adjacent stope, and the water pressure of the filling retaining wall mainly depends on the speed of the filter passing through the retaining wall.

South Africa has proposed new filling design standards for existing filling design standards for ultra-deep well mining research, suggesting that 60% to 70% of the goaf should be filled.

3 paste filling

The Australian Mount Isa Mine uses two simple, cost-effective test methods to study paste characteristics when developing paste filling techniques, to help paste filling design, ie flow cone test and small slump cone test. Through these tests, the flow characteristics of the paste can be predicted. The flow cone consists of a cone and a section of outlet tube with a cone angle of 14° and a volume of 2 L. The outlet tube has an inner diameter of 30 mm and a length of 150 mm and is connected to the cone. The small slump cone test is based on the standard slump test of the building. The data shows that the typical slump of the paste is 150-250 mm, the slump of the concrete is 30-60 mm, and the slump of the pumped concrete is 100-125 mm.

The Clinton Mine Paste Filling System in Australia was not operating properly during the first 18 months of operation. Most of the problems were related to pipe wear. Later, ceramic and rubber gaskets were used in the wearable areas to reduce wear. Greatly reduce downtime. At the beginning of the filling, two batches of slurry without added cement are prepared and filled into the pipeline for the purpose of wetting the pipe and then adding cement. At the end of the operation, 2 to 3 batches of cement-free slurry are also charged, and then the pipeline is cleaned with water and air. An air pressure gauge is installed on the surface to determine if the pipe is clean. At the beginning of the air supply, the pressure reached 700 kPa due to the slurry and water in the pipe, and the pressure gradually decreased to 200 kPa, at which time the slurry and water in the pipe were cleaned. If the paste has not yet entered the pipeline within 20 minutes, the pipeline will be cleaned manually or automatically. Since the paste is fed into the pipeline in batches, high dynamic loads are generated in the downhole pipeline. During the first 18 months of operation, due to the dynamic load, the joints of the pipeline are often damaged. To this end, the following measures are taken: The knife-gate (gate knife) type valve is used to limit the flow rate to ensure the semi-continuous flow of the paste in the pipeline; the flange is used to replace the tongue-and-groove tube at the position susceptible to high dynamic load; and the slump is reduced; Install the double flange tube in the appropriate place. The Clinton Mine has established a standard that when the paste has a yield stress of 800 Pa (approximately 85% solids concentration), the paste can be successfully filled. The mine is the first mine in Australia to apply paste filling technology and has achieved many successful experiences.

The Neves Corvo mine in Portugal studied the strength of the paste filling mine and the relationship between laboratory test values ​​and field values. The liquefaction of the paste in the second step of the mine was also studied. The results of laboratory tests and field tests showed that adding 2% cement, the possibility of liquefaction of the paste filling is small, and when adding 0.5% cement, Liquefaction is highly likely, so it is common to add 1% cement to avoid liquefaction. When minimizing the risk of liquefaction, the 28-day uniaxial compressive strength should reach 172 kPa, the cement addition at this time is about 1.5%, and the filling body can reach 10 m.

The Brunswick mine in Canada decided to build a paste filling system in July 1997. Prior to this, the tailings test, loop transport test and pre-feasibility study were completed. The entire system invested $24.1 million. The filling station is controlled by a programmable logic controller (PLCS) hybrid computer system and a Fisher Provox Distributed Control System (DCS). The PLCS processes the digital information, turns on the sequence of the motor and valve, and the DCS processes the analog information to provide an interface for the operator. A processing information system (PI) is used as a database and provides sensor orientation for analysis by filling station operators and technicians. Install 5 mobile cameras at the outlet of the filling pipe to monitor the filling. The video signal is sent to the surface filling station via a set of (Leaky feeder) communication systems and fiber optics. If the filling is drilled into the stop, install an ultrasonic flow meter as close as possible to the outlet to monitor the filling. In the downhole pipeline, 18 sensors are installed to continuously monitor the pressure in the pipeline. The pressure signal is monitored by the downhole PLCS and then transmitted back to the surface filling station via a data cable and fiber optic network. The system also has a Leaky feeder radio communication system for voice communication. The paste mixing at the Brunswick mine uses a blade mixer for continuous operation, unlike traditional batch mixing. Practice has proved that the blade mixer works reliably. Cement is added wet.

In the feasibility study stage, the test results are: solid weight content of 81% to 83%, corresponding slump 178 ~ 254 mm, suitable for preparation and transport. In actual production, the solid weight concentration is 78% to 80%. According to the current change of the mixer, cement can be accurately added and the slump is maintained between 140 and 165 mm.

Japan introduced the Toyoha mine plan to introduce paste filling technology, the main purpose is to prevent heat flow from the goaf and improve the downhole climate. The underground temperature is 10 to 20 times the average temperature of the Japanese islands, and the highest temperature measured in the borehole reaches 242 °C. The mine only completed the surface loop test and the second test was planned downhole.

A mine in Canada studied the compatibility between the rheological properties of the paste and the filling pipe network. The conclusion of the study is that the problem of paste filling comes from one or more of the following aspects: pipe network design, aggregate level With design, water-cement ratio or production process. These issues can be minimized during the design phase. When the rheological properties of the paste are incompatible with the pipe network, a large number of failures will occur. In the pipe network design phase, the pipe diameter, aggregate grading and water-cement ratio determine the operating state of the system, so the system's adaptability should be considered during the design phase. Strength and rheological properties tests should be performed at the same time, not only to meet the strength requirements, but also to ensure that the rheological properties are compatible with the pipe network. The basic principle of design and what must be done is to ensure that the pipe network is compatible with the rheology of the paste.

4 filling equipment and operation

A typical example is the optimization of filling equipment for high concentration filling of the Stratoni mine in Greece. The mine is located in northeast Greece, mining lead and zinc ore to the approach adopted under the filling method. Due to the difficulty in conveying, the filling body beam is often damaged. Therefore, relying on the addition of cement to solve, resulting in increased filling costs, and the construction of a new filling station, economically unreasonable. The solution is to optimize and retrofit existing filling systems, with an investment of only $35,000. Cement consumption accounts for a considerable proportion of operating costs, saving 1% of cement, and the mine can save $50,000 per year. Optimization measures included changing the diameter of the shaft to 100 mm and changing the diameter of the shaft to 125 mm to prevent precipitation of particles in the pipeline. In addition, in order to improve the filling consistency, a control facility is added in the filling station, and the program consistency logic (PLC) is installed on the filling system by controlling the current consistency of the slurry by the metering disc mixer.

Germany has studied advanced filling equipment to reduce or eliminate wear and corrosion methods in filling equipment. The filling pipeline mainly uses basalt- lined steel pipes, which are pressure-resistant and the pipes are flanged. The lining prevents wear and corrosion and provides an almost polished surface.

Australia's Olympic Dam mine uses a deep-hole empty field method, with empty gravel cement filling and stone filling. The filling material enters the top of the stope through the borehole from the surface. Due to the adverse effects of the dust and humid air in the stope, the filling process cannot be observed by the naked eye. To this end, a millimeter-wave radar is developed. Using this radar to observe the filling process and obtain real-time data of the relative positions of different filling bodies is an effective means to control the filling of the stope.

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