Application of post-filling mining method in sublevel caving stage in irregular thick ore body

A domestic tungsten mine has been produced for several decades. Previously it was small-scale mining. After expansion, it reached 1.485 million t/a and the service life was about 25 years. Due to the large extent of the mining area and the length of the ore body, the occurrence of the production is severe, and the mining technical conditions vary greatly. It is obviously unreasonable for the mine to use the same mining method. At present, the mine adopts the shallow hole retention method for the steeply inclined thin ore body, which has the characteristics of high efficiency and safe operation. However, for the irregular low-grade thick ore body, the mining method and other mining methods are difficult to carry and remove the ore. Problems such as large depletion rate, poor safety conditions, and low production efficiency [1-3]. The thick ore body is the first mining area after the mine expansion and transformation is put into operation, and whether the mining method is reasonable is critical to the future production of the mine. At present, the price of tungsten concentrate products is further lower than that of mine expansion design. The pressure on mine production costs is high. Under the current market conditions and mining technology conditions, the research and optimization of mining methods can effectively control and reduce production costs and ensure corporate profits. It is a subject that must be studied intensively [4-5].
01
1 mining technical conditions
Irregular low-grade thick ore body mainly refers to the II11 ore body in the south mining area of ​​the mine. It belongs to the contact metasomal skarn type scheelite ore body, which is produced in the positive contact zone between the top of the granite and the limestone. Intrusion of surrounding rock limestone, no large faults in the mining area, stable rock, single shape, good hydrogeological conditions; ore body trend is similar to north and south, tending to east, dip
It is 10°～90°; the ore body space has a large change in shape, which is lenticular, irregular thin plate and other output, and the thickness of the ore body is very different.

The experimental stope of this mining method research selects the 160~250m elevation of the south mining area, the 13-14 exploration line, and the Y11 ore body of Y=38394000～38394200m. The thickness of the ore body varies greatly, with an average thickness of 23m and an average inclination of 58°. The ore body of 160~200m elevation is continuous and thick, and some of the inclusions are embedded with the thickness of more than 20m. The ore body of 200~250m elevation has evolved into three branches. The thickness of a few ore bodies in the branch is only ten meters, most of which are More than 20m. Multiple top and bottom slate stone ore skarn, granite, marble, and limestone, hard solid ore, a density of 3.16t / m3, f = 8 ~ 10, the coefficient of 1.5 to 1.6 loose The natural angle of repose is 45°; the rock density is 2.6 to 2.8 t/m3, f=8 to 12, the looseness coefficient is 1.5 to 1.7, and the natural angle of repose is 45°. The three-dimensional geological model of the ore body in the test mining section is shown in Figure 1.

2 mining method selection
The first mining area of ​​the tungsten mine is an irregular low-grade inclined to steeply inclined thick ore body, and the ore rock has good stability. According to the characteristics of occurrence, mining technical conditions and national technical and economic policies, it is appropriate to start from the current technical management level of the mine. The mining method is adopted to ensure the ore grade, investment, simple process, less operation, and convenient management.
Due to the serious mining situation of the miners, there are many goafs, and the surface is not allowed to collapse. In view of ensuring the ore grade and eliminating the caving method, the feasible mining methods mainly include the open field method and the empty field type post-filling mining method. Due to the low value of raw ore mining, in the current technical and economic conditions, in order to reduce the mining cost, the mining area has the conditions for stockpiling tailings. The method of first empty field and post-filling filling is adopted to reduce the loss of lean and improve the recovery rate. And the purpose of protecting the surface. According to the mining experience of mines with similar conditions at home and abroad, combined with the requirements of the production capacity of the mine, comparative analysis of various mining methods, layer screening, determination of the use of medium and deep hole sublevel caving stage, mining, post-filling mining method is more suitable for the irregularity of the mine The ore body is characterized by its technical economy [6-7].
3 Application of post-filling mining method in mining area of ​​medium and deep hole sublevel caving stage
3.1 Stope layout and structural parameters
The area is divided into 100m along the ore body, and a 15m wide pillar is left between the panels. The vertical ore body in each panel is divided into a mine room and a mine room column. The length of the mine is 40m (adjusted with the thickness of the ore body), the width is 20m, the column width of the mine room is 10m, and the top column is 10m thick. The bottom structure of the trench is used to discharge the scraper. The middle section is 90m high (160~250m middle section) and is divided into five stages of 170, 185, 200, 215, 230m, of which 170m is the non-track concentrated ore section and 160m is the middle section of the orbital centralized transportation. In order to facilitate the mining, a slippery mine is arranged along the ore body every 100m. The method of filling and mining of the mine in the middle and deep hole sublevel caving stage is shown in Figure 2.

3.2 mining cutting
The mining engineering mainly includes segmented roadway, mining roadway, mining roadway, sectioned rock drilling roadway, sectioned rock drilling roadway, slipway contact road, ore slipway, etc.; , cutting cross lanes, cutting patios, etc.
A bottoming roadway is arranged at the bottom of the mine house, and a fan-shaped medium-deep hole is drilled in the roadway, and a concentrating trench is formed after the blasting; the segmented roadway is arranged outside the lower part of the ore body, and the segmented roadway is every step. 10~12m will be used to excavate the ore approaching into the minehouse at 45°, and connect with the ore collecting trench to form the ore outbound channel. At the end of each stope, 2.5 to the recovery boundary
3m to dig a cutting ventilation patio and a cutting crossway to form a continuous airflow between the stope and the upper and lower sections. The cutting ventilation patio is connected with the upper section rock drilling road and the upper middle section roadway, and is drilled in the cutting cross section. Parallel to the deep hole, the cutting patio is used as a free surface to form a cutting groove [8].
3.3 mining process
A step-by-step empty-field mining room is opened, and the tailings are cemented to fill the mining room. After the cement body reaches a certain strength, the two-step segmented empty field is used to open the mining column, and the post-filling is filled. The bottom of the pillar is filled with full tailings cement 10m. In order to reduce the filling cost, the top and bottom pillars will be recovered in the next stage, and the remaining empty areas will be filled with non-cemented solid tailings and waste rock. Mining house mining
Starting from the cutting slot, the mining is carried out at the other end of the mine; the sections are harvested from top to bottom, and the upper section is advanced 2 to 3 rows of blastholes to form a stepped working surface [9-10].
3.3.1 Rock drilling
The YGZ-90 rock drill is equipped with a disc bracket to drill the upper fan-shaped medium-deep hole in the section rock drilling roadway with a hole diameter of 60-65mm. Each YSC-45 rock drill is used to assist in drilling individual side holes.
The drilling method is a common rock drilling method used in the mining method of the medium-deep hole sublevel caving stage. In order to reduce the large block rate, the eye-catching mode, the parameters of the hole and the charge amount can be controlled. Before the mining, the cutting patio is opened to form a cutting groove. The drilling parameters of the deep hole in the trough are 1 to 1.2 m, and the bottom distance is 2 m. The parameters of the deep hole drilling in the mining are 1.2-1.5m, and the bottom distance is 1.8~3m. Due to the good stability of the ore, the middle and deep holes near the top plate should be over 0.5m deep.
3.3.2 Blasting
After the blasthole is finished, the cutting groove is used as the initial free surface lateral single-stage split blasting or multi-stage simultaneous blasting, and each blasting 3 to 5 rows of blastholes. The BQF-100 charger is used to fill the powdered ammonium explosives. The non-conducting squib detonators are slightly detonated, the same row and the same segment, each row is segmented, and the detonating tube is connected in parallel.
3.3.3 Stope ventilation
At the time of mining, the fresh air flow from the stopway passes through the section roadway and the various loading roads to reach the mining face; when rock drilling, the fresh air flow from the slope passes through the section roadway and section rock drilling The roadway reaches the rock drilling face. The dirty wind after cleaning the working face is merged into the return air duct of the previous section through the cut return air courtyard, and then the surface is extracted through the return air well.

In order to improve the ventilation effect of the working face, the local fan is used for ventilating during the rock drilling and after the blasting.
3.3.4 support
The section rock drilling road, the bottom structure of the mine, and the pedestrian well are generally not supported. For the unstable section, the bolt or spray anchor net is used for support. The shotcrete is 100mm thick and the concrete strength grade is C20. distance of 800mm × 800mm, metal mesh specification is 1.8m × 1.8m.
3.3.5 mining
Mining with CY-2 2.0m3 diesel scraper. The ore under the caving is concentrated in the 170m section trench, which is transported from the outbound mine to the stopway by the scraper and slipped to the mid-160m loading.
3.3.6 filling process
After the mining and mining columns are harvested and mined, the goaf is filled with helium. Before filling, the roadway leading to the stope is closed, and the filling and retaining wall is constructed in the bottom of the stope. The filling water pipe is laid from top to bottom, and the cutting return air patio and the upper middle section are used as filling channels.
The mined area of ​​the mine is filled with full tailings cement. The cement material is C32.5, the filling slurry concentration is controlled at 68%~72%, the bottom of the empty area is 1:4 lime sand ratio, and the filling height is 10m. The lower part adopts a 1:6 lime-sand ratio and the filling height is 7m; the upper part of the stope adopts a 1:8 lime-sand ratio and is filled to the upper stage. The bottom of the mined-out area of ​​the pillar is filled with cement with full tailings. The ratio of sand to sand is 1:4 and the filling height is 10m. The upper part is filled with non-cemented waste rock and tailings.
4 test mining effect
The main technical and economic indicators of the test mining stope are shown in Table 1. It can be known that the production capacity of a single stope can reach 518t/d, as long as the four stopries can be harvested at the same time to meet the requirements of the production capacity of 2000t/d. The medium-deep hole sublevel caving stage mine post-filling mining method effectively reduces the depletion rate, loss rate, explosive unit consumption, and kilotons.
The mining ratio and mining costs increase mining efficiency and increase economic efficiency. The test results are ideal and have reached the expected targets.

5 Conclusion
The domestic reserves of a certain tungsten ore have a reserve of more than 70 million tons. The irregular low-grade and large ore bodies account for a large proportion. According to the technical conditions of the ore mining, the mining in the sublevel caving stage is followed by the mining method, which is divided into two steps. Back mining, one step back to the mining room, after the full tail sand cement filling, two steps back to the mining column, non-cemented filling. Shallow with the original
Compared with the hole retention method, the mining method has a high degree of mechanization, safe operating conditions, convenient management, and large recovery strength, which can greatly increase production capacity and reduce mining costs. Through industrial tests, good technical and economic indicators have been obtained. In the sublevel caving stage, the successful application of the post-filling mining method in the irregular low-grade thick ore body provides a reference for mines with similar technical conditions.

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Article source: "Modern Mining", 2016.12
Author: Ting-Ting Hu; Resources and Safety Engineering, Central South University, Hunan Nonferrous Metal Research Institute;
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